Worksheet Thermochemistry 41y41
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1st worksheet SYSTEM AND SURROUNDING EXOTHERMIC AND ENDOTHERMIC REACTION THERMOCHEMISTRY EQUATION CHARACTERISTICS OF ENTHALPY CHANGE Drs. M. Hariyanto SMA Negeri 3 Malang (State Senior High School) Jl. Sultan Agung Utara No 7 Phone (0341) 324 768 Malang 65111 (website : http://psb-sman3malang.com )
Before we study about Thermochemistry, we should review the previous material: substances that involved in reaction, what is relationship between number of moles of substances in reaction and coefficient, physical states of substance, the evidences of chemical reaction, and units of energy and heat. Answer the following questions! No Questions 1 Identify, which substances that called reactants and products in the following reaction: Ca(OH)2(aq)+2HCl(aq) →CaCl2(aq) +2H2O(l) 2 a. Balance the following reaction: ..(NH4)2SO4(aq)+.. KOH(aq) →.. K2SO4(aq)+ …H2O(l)+ .. NH3(g) b. Write the proportional of number of moles of each substance! c. If 2 moles of ammonium sulfate react with 2 moles of potassium hydroxide, how many moles of potassium sulfate and ammonia gas that produced?
Answer Reactants: ………………………….. Products :…………………………… a. …………………………………… b. …………………………………….. c. ……………………………………..
3
Mention the physical states that you knew before!
………………………………………….. …………………………………………..
4
How to write the chemical formula of the following substances: a. Hydrogen gas b. Oxygen gas c. Nitrogen gas d. Fluorine gas e. Chlorine gas f. Bromine liquid g. Iodine solid
………………….. ………………….. ………………….. ………………….. ………………….. ………………….. …………………..
Thermochemistry/sman3malang/;by m. hariyanto
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h. i. j. k. l.
4
5
Phosphorus Sulfur Iron Carbon Glucose that consists of 6 atoms of C, 12 atoms of H, and 6 atoms of O per molecule m. Barium phosphate n. Aluminum sulfate Give the evidences or phenomena that accompany the chemical reaction What is heat? What is the unit of heat?
………………….. ………………………. ………………………. ………………………. ................... ………………………. ………………………. ……………………………………………….. ………………………………………….. ………………………………………….. ………………………………………….. ………………………………………….. …………………………………………..
System and Surrounding Purposes
Students are able to: Identify the system and the surroundings for chemical reactions.
Assignment
Observe the following figure and complete the blank! Cases Figures System Student is observing Aqueous solution of aqueous solution of sodium hydroxide Sodium hydroxide in test-tube
Teacher is observing mixture of aqueous solutions of silver nitrate and hydrochloric acid aqueous solution react to produce silver chloride solid and nitric acid aqueous solution in Erlenmeyer-flask
Surrounding -Test-tube -space outside of test-tube
……………………..
………………………
……………………..
………………………
………………………
………………………
……………………..
……………………..
Thermochemistry/sman3malang/;by m. hariyanto
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Conclusion
Based on your observation of the cases above, conclude and describe the definition of system and surrounding!
Exothermic and Endothermic Reaction Based on heat or energy that accompany (absorbed or released by) the system, chemical reaction classified into 2 (two) types), that is exothermic and endothermic reaction. Heat or energy moves/flows from system to the surroundings or the other around way. How heat for chemical reactions can be expressed? What is exothermic reaction? What is endothermic reaction? To answer the questions above, please do the activity below!
Purposes
Students are able to: 1. describe how heat for chemical reactions can be expressed as the change of enthalpy, ∆H 2. Identify the characteristics of exothermic and endothermic reactions.
Information of Enthalpy,H and Enthalpy Change, ∆H
1. Enthalpy (H) or heat content is chemical energy stored within a substance is a type of potential energy. 2. Enthalpy change (∆H) is the amount of heat released or absorbed by system at constant pressure. Enthalpy change of chemical reaction can be expressed as follows: ∆H = Hproducts - Hreactants 3. The value of enthalpy change, ∆H depend on the amount of enthalpy of reactants and enthalpy of products. If enthalpy of products is more than enthalpy of reactants, the value of ∆H is positive, the system absorbed heat from the surrounding. In the other way, if enthalpy of product is less than enthalpy of reactant, the value of ∆H is negative, the system release heat to the surrounding.
Thermochemistry/sman3malang/;by m. hariyanto
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Experiment of exothermic and endothermic reaction a. Equipments and materials No Equipments/materials 1 Thermometer 2 Glass beaker 3 Plastic teaspoon 4 NaOH solid 5 NaCl solid 6 NH4Cl solid 7 Distilled water
Capacity -10 to 100˚C 100 mL -
Number 1 3 3 1.5 teaspoon 1.5 teaspoon 1.5 teaspoon 50 mL
b. Procedure 1) Place about 15 mL of distilled water in a 100 mL glass beaker and measure its temperature. Add one half of teaspoon of sodium hydroxide solid, stir gently, and record any change in temperature. 2) Repeat procedure 1) using one half of teaspoon of ammonium chloride 3) Repeat procedure 1) using one half of teaspoon of sodium chloride c. Data observation Experiment 1 2 3
Solute ………….. ………….. …………..
Solvent ………….. ………….. …………..
Initial temperature ………….. ………….. …………..
Final Type of temperature process ………….. ………….. ………….. ………….. ………….. …………..
NOTE: 1. Type of process is exothermic reaction, if final temperature is more than initial temperature 2. Type of process is endothermic reaction, if final temperature is less than initial temperature d. Assignment Based on the data above, answer the following questions No Questions Answer 1 The system releases heat to the ……………………………………………………………… surroundings if final temperature is more than initial temperature. …………………………………………………………….. What is the type of process? 2 The system absorbs heat from the ……………………………………………………………… surroundings if final temperature is less than initial temperature. …………………………………………………………….. What is the type of process? 3 Based on the answers of questions ……………………………………………………………… no 1, a. which experiment that called …………………………………………………………….. exothermic reaction?
Thermochemistry/sman3malang/;by m. hariyanto
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b. which experiment that called endothermic reaction? 4
What do you think of the value of enthalpy change of a. exothermic reaction? b. Endothermic change?
……………………………………………………………… ……………………………………………………………..
e. Conclusion Conclude the characteristic of each type of process (exothermic and endothermic) about flowing of heat, amount of enthalpy of system and surroundings (or product and reactant), and the value of enthalpy change!
Additional Notes
Thermochemistry/sman3malang/;by m. hariyanto
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Thermochemistry Equation and Characteristics of Enthalpy Change After understanding the enthalpy, enthalpy change, and characteristics of exothermic reaction and endothermic reaction, now how to express the equation of reaction with energy/heat that accompany? And what are the characteristics of enthalpy change? To answer them, do the following activity!
A. THERMOCHEMISTRY EQUATION
Purpose
Students are able to: express/write the thermochemistry equation
Assignment 1. Observe and complete the following table No 1
2
3
4
5
Process 0.5 moles of nitrogen gas with 1.5 moles of hydrogen gas react to produce 1 mole of ammonia gas by releasing 46 kJ of heat 1 mole of nitrogen gas with 3 moles of hydrogen gas react to produce 2 mole of ammonia gas by releasing 92 kJ of heat 2 mole of carbon solid with 1 mole of hydrogen gas react to produce 1 mole of acetylene (C2H2) gas by absorbing 227 kJ of heat 4 mole of carbon solid with 2 moles of hydrogen gas react to produce 2 moles of acetylene (C2H2) gas by absorbing 554 kJ of heat 1 mole of carbon solid with 2 moles of hydrogen gas react to produce 1 mole of methane (CH4) gas by releasing 75 kJ of heat
Thermochemistry Equation 0.5 N2(g) + 3/2 H2(g) → NH3(g) ∆H=-46 kJ
N2(g) + 3 H2(g) → 2NH3(g)
2C(s) + H2(g) → C2H2(g)
∆H=-92 kJ
∆H=+227 kJ
…………………………………………………………………
…………………………………………………………………
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6
7
8
3 moles of carbon solid with 6 moles of hydrogen gas react to produce 3 mole of methane (CH4) gas by releasing … kJ of heat 2 moles of carbon solid, 3 moles of hydrogen gas, and 0.5 moles of oxygen gas react to produce 1 mole of ethanol (C2H5OH ) liquid by releasing 278 kJ of heat 1 mole of carbon solid, 1.5 moles of hydrogen gas, and 0.25 moles of oxygen gas react to produce 0.5 moles of ethanol (C2H5OH ) liquid by releasing … kJ of heat
…………………………………………………………………
…………………………………………………………………
…………………………………………………………………
2. Answer the following questions No 1
Question Please observe the process and their thermochemistry equation above. Identify what anything that thermochemistry equation) described/shown?
Answer ………………………………………………………. ………………………………………………………. ………………………………………………………. ………………………………………………………. ……………………………………………………….
Conclusion Based on the answer of question above, describe the definition of thermochemistry equation!
B. THE CHARACTERISTICS OF ENTHALPY CHANGE
Purpose
Students are able to: describe the characteristics of enthalpy change
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Assignment 1. Observe and complete the following table a. The relationship between enthalpy change and number of mole of substance No Process Thermochemistry Equation 1 2 moles of carbon solid, 3 moles of hydrogen gas, and 0.5 moles ………………………………………………………………… of oxygen gas react to produce 1 mole of ethanol (C2H5OH ) liquid by releasing 278 kJ of heat 2 1 mole of carbon solid, 1.5 moles of hydrogen gas, and 0.25 ………………………………………………………………… moles of oxygen gas react to produce 0.5 moles of ethanol (C2H5OH ) liquid by releasing … kJ of heat
No 1
2
b. The relationship between enthalpy change and direction of reaction Process Thermochemistry Equation 0.5 moles of nitrogen gas with 1.5 moles of hydrogen gas react ………………………………………………………………… to produce 1 mole of ammonia gas by releasing 46 kJ of heat 1 mole of ammonia gas decomposes to produce 0.5 ………………………………………………………………… moles of nitrogen gas with 1.5 moles of hydrogen gas by absorbing 46 kJ of heat
c. The relationship between enthalpy change of some reactions and enthalpy change of total reaction No Process Thermochemistry Equation 1 Reaction I 1 mole of nitrogen gas and 1 mole ………………………………………………………………… of oxygen gas react to produce 2 mole of nitrogen monoxide by absorbing 180 kJ of heat 2 Reaction II 2 moles of nitrogen monoxide gas ………………………………………………………………… and 1 mole of oxygen gas react to produce 2 mole of nitrogen dioxide by releasing 112 kJ of heat
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3
Reaction III 1 moles of nitrogen gas and 2 mole of oxygen gas react to produce 2 mole of nitrogen dioxide by absorbing 68 kJ of heat
Reaction I :………………………………………………… Reaction II :…………………………………………………+ Reaction III:………………………………………………..
2. Answer the following questions No 1 2 3
Questions What is the relationship between enthalpy change and number of mole of substance in thermochemistry equation? What is the relationship between enthalpy change and direction of reaction in thermochemistry equation? What is the relationship between enthalpy change of some reactions and enthalpy change of total reaction in thermochemistry equation?
Answer …………………………………………………. …………………………………………………. ………………………………………………….
Conclusion
01. Identify the systems and the surroundings for: a. mixture of aqueous solution of barium nitrate and aqueous solution of sulfuric acid that placed in the glass beaker b. mixture of aqueous solution of Lead(II) nitrate and aqueous solution of sodium iodide that placed in the test tube c. reaction of nitrogen gas and oxygen gas to produce nitrogen monoxide in the air
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02. Identify the following process are endothermic or exothermic reaction! a. reaction of aqueous solution of sodium hydroxide and aqueous solution of hydrochloric acid in test tube so temperature of test tube wall increases 10˚C b. combustion of methane gas to produce 888 kJ of heat c. dissolving of urea in the water in test tube so the temperature of test tube is decreasing d. N2(g) + 2O2(g) → 2NO(g) – 68 kJ e. C(graphite) + O2 → CO2(g) ∆H=-393.5 kJ f. Given the diagram of energy of carbon disulfide formation below: H 4CS2(g) Product 4C(s)+ S8(v) Ractants
03. Write the thermochemistry equation of the following process! a. 1 mole of hydrogen gas and 0.5 moles of oxygen gas react to produce vapor of water by releasing 285.8 kJ of heat. b. 2 moles of carbon solid and 2 mole of hydrogen gas react to give 1 moles of ethylene (C2H4) gas by absorbing 52 kJ of heat.
04. Given: 2H2(g) + O2(g) → 2H2O(l) ∆H=-571.6 kJ a. Calculate the heat that released by formation of 1 mole of water vapor b. Calculate the heat that released by formation of 9 grams of water vapor c. Calculate the heat that released by decomposition of 1 mole of water vapor to produce hydrogen gas and oxygen gas
Thermochemistry/sman3malang/;by m. hariyanto
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d. Calculate the heat that released by decomposition of 3.6 grams of water vapor to produce hydrogen gas and oxygen gas.
05. Given: Reaction I : C(graphite) + ½ O2(g) → CO(g) ∆H=-110.5 kJ ∆H=-282 kJ Reaction II : CO(g) + ½ O2(g) → CO2(g) Calculate enthalpy change of the following reaction: C(graphite) + O2(g) → CO2(g)
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2nd worksheet TYPE OF ENTHALPY CHANGE Drs. M. Hariyanto SMA Negeri 3 Malang (State Senior High School) Jl. Sultan Agung Utara No 7 Phone (0341) 324 768 Malang 65111 (website : http://psb-sman3malang.com )
We should review the previous material: exothermic and endothermic reaction, thermochemistry equation, and characteristics of enthalpy change. We also study the type of reaction before. How many types of enthalpy change? How to determine the magnitude of each enthalpy change? Answer the following questions! No Questions Given: H2(g) +1/2 O2(g)→2H2O(l) ∆H=-235.8 kJ T
a. Identify the reaction above is exothermic or endothermic. b. Calculate the heat that released/absorbed by formation of 3.6 g of water vapor c. Calculate the heat that released/absorbed by decomposition of 4.5 grams of water vapor
2
What factors that determine the value and magnitude of enthalpy change? (Please answer based on the activity 3b worksheet 1)
Answer 1. ………………………………………… 2. ……………………………………….. ……………………………………….. ……………………………………….. 3. ……………………………………….. ……………………………………….. ……………………………………….. …………………………………… .………………………………….. …………………………………… .…………………………………..
Information
Standard Enthalpy Change (∆H˚) Standard enthalpy change is symbolized by ∆H˚ (delta H degree or delta H zero). Standard enthalpy change is measured at standard state 1. For compound - The standard state of a gaseous substance is pressure of exactly 1 atmosphere - The standard state of a substance present in a solution, standard state is a concentration of exactly 1 M - The standard state of pure substance in a condensed state (liquid or solid), standard state is the pure or liquid 2. For element - The standard state of an element is the form in which the element exists under condition of 1 atmosphere and 25˚C.
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Type of Reaction Purposes
Students are able to: Identify the type of chemical reactions.
Assignments
1) Observe the following reactions (Please do at your home before doing activity 2) a) Physical Change No Process Type of Process 1 H2O(s) → H2O(l) Melting 2 H2O(l) → H2O(g) Evaporation 3 H2O(s) → H2O(g) Sublimation No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
b) Chemical Change/reaction Reaction C(s) + 2H2(g) → CH4(g) H2(g) +S(s) + 2O2(g) → H2SO4(l) 2Cs) +3H2(g) +1/2 O2(g) → C2H5OH(l) CH4(g) → C(s) + 2H2(g) H2SO4(l) → H2(g) +S(s) + 2O2(g) C2H5OH(l) → 2Cs) +3H2(g) +1/2 O2(g) C(s) + O2(g) → CO2(g) S(s) + O2(g) → SO2(g) CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l) H2(g) → 2H(g) O2(g) → 2O(g) N2(g) → 2N(g) CH4(g) → C(g) + 4H(g) H2O(g) →….. + …….. NaCl(s) → NaCl(aq) C6H12O6(s) → C6H12O6(aq) NaOH(s) → ………… HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq) + 2H2O(l)
Thermochemistry/sman3malang/;by m. hariyanto
Type of Reaction Formation Formation ………………………. Decomposition ………………………. ………………………. Combustion Combustion ……………………… ………………………. Atomization Atomization Atomization Atomization Atomization Dissolving Dissolving Dissolving Neutralization Neutralization
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2) Based on the tables above, answer the following question! No Questions Answer 1 Based on the process at physical change table, observe the physical states of each reactant a. ………………………………………… and product, and the name of process. ……………………………………….. a. What is melting process? b. What is melting evaporation? b. ……………………………………….. c. What is melting sublimation? ……………………………………….. c. ……………………………………….. ……………………………………….. 2
Based on reaction of formation (reaction 1,2, and 3 at table of chemical change above): a. Identify (element or compound) the reactants and products of reactions b. What is formation reaction? Based on reaction of decomposition (reaction 4,5, and 6 at table of chemical change above): a. Identify (element or compound) the reactants and products of reactions b. What is formation decomposition? Based on reaction of combustion (reaction 7,8,9 and 10 at table of chemical change above): a. Identify the element that reacts with substances (C, S, CH4, and C6H12O6) b. What is combustion reaction?
a. …………………………………………….. …………………………………………….. b. …………………………………………….. ……………………………………………..
5
Based on reaction of atomization (reaction 11-15 at table of chemical change above): a. Identify (element or atom) the reactants and products of the reactions! b. What is atomization reaction?
a. …………………………………………….. …………………………………………….. b. …………………………………………….. ……………………………………………..
6
Based on the process at dissolving (reaction 16-18 at chemical change above),: a. Identify the physical states of each reactant and product b. What is dissolving process?
a. …………………………………………….. …………………………………………….. b. …………………………………………….. .…………………………………………..
7
Based on reaction of neutralization (reaction 19-20 at table of chemical change above): c. Identify (acid, base, or salt) the reactants the reactions! d. What is neutralization reaction?
a. …………………………………………….. …………………………………………….. b. …………………………………………….. ……………………………………………..
3
4
Thermochemistry/sman3malang/;by m. hariyanto
a. …………………………………………….. …………………………………………….. b. …………………………………………….. …………………………………………….. a. …………………………………………….. …………………………………………….. b. …………………………………………….. ……………………………………………..
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3) Conclude the definition of each type of reaction/process by completing the following table! No 1
Process/Reaction Melting
2
Evaporation
3
Sublimation
4
Formation
5
Decomposition
6
Combustion
7
Atomization
8
Dissolving
8
Neutralization
Thermochemistry/sman3malang/;by m. hariyanto
Definition
General Equation X(s) → X(l)
Element X + element Y → Compound XY
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Type of Enthalpy Change After understanding the type of process/reaction, the following activity you are going to study about the type of enthalpy change. How many types of enthalpy change in thermochemistry? How to write the equation for each enthalpy change? To answer the questions, please do the following activity!
Purposes
Students are able to: 1. write the equation for the standard enthalpy of formation 2. write the equation for the standard enthalpy of combustion 3. write the equation for the standard enthalpy of atomization 4. write the equation for the standard enthalpy of solution 5. write the equation for the standard enthalpy of neutralization
Assignments
1) Observe and complete the following table! (Enthalpy is measured at 1 atmospheric pressure and 25˚C)
No
Thermochemistry Equation
Type of Process
Type of Enthalpy
1
1H2O(s) → H2O(l) ∆H=+6.02 kJ
………………….
Standard enthalpy of 0
fusion (∆ H fus ) 2
1H2O(l) → H2O(g) ∆H=+41.1 kJ
.………………….
Standard enthalpy of 0
vaporization (∆ H vap ) 3
1H2O(s) → H2O(g) ∆H=+47.12 kJ
.………………….
Standard enthalpy of 0
sublimation (∆ H sub ) 4
C(s) + O2(g) → 1CO2(g) ∆H=-393.5 kJ
.………………….
Standard enthalpy of 0
formation (∆ H f ) 5
2C(s) + H2(g) →1 C2H2(g) ∆H=+226.7 kJ
.………………….
Standard enthalpy of 0
formation (∆ H f ) 6
1C2H6(g) +7/2 O2(g) → 2CO2(g) + 3H2O(l) ∆H=-1560kJ
.………………….
Standard enthalpy of 0
combustion (∆ H c ) 7
1C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l) ∆H=-2220kJ
.………………….
Standard enthalpy of 0
combustion (∆ H c ) 8
1C6H6(g) +15/2 O2(g) → 6CO2(g) + 3H2O(l) ∆H=-3293kJ
.………………….
Standard enthalpy of 0
combustion (∆ H c )
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9
1H2(g) → 2H(g)
∆H=+432 kJ
.………………….
Standard enthalpy of 0
atomization (∆ H a ) 10
1HF(g) → H(g) + F(g) ∆H=+565 kJ
.………………….
Standard enthalpy of 0
atomization (∆ H a ) 11
1NaOH(s) → NaOH(aq) ∆H=-42.7 kJ
.………………….
Standard enthalpy of 0
solution (∆ H sol ) 12
1Na2NO3(s) → Na2NO3 (aq) ∆H=+20.5 kJ
.………………….
Standard enthalpy of 0
solution (∆ H sol ) 13
HCl(aq)+NaOH(aq)→ NaCl(aq) +1H2O(l) ∆H=-57.1 kJ
.………………….
Standard enthalpy of neutralization 0
(∆ H neut ) 14
HNO3(aq)+KOH(aq)→ KNO3(aq) +1H2O(l) ∆H=-57.3 kJ
.………………….
Standard enthalpy of neutralization 0
(∆ H neut )
2) Based on the data above answer the following questions No Questions 1 Based on the thermochemistry equation table above (no 1,2, and 3) a. How many moles of substances that melted, evaporated, and sublimated? b. What is standard enthalpy of fusion? c. What is standard enthalpy of vaporization? d. What is standard enthalpy of sublimation?
Answer a. ………………………………………… ……………………………………….. b. ……………………………………….. ……………………………………….. c. ……………………………………….. ……………………………………….. d. ……………………………………….. ………………………………………..
2
Based on the thermochemistry equation table above (no 4 and 5) a. How many moles of compound that form their elements? b. What is standard enthalpy of formation?
a. ………………………………………… ……………………………………….. b. ……………………………………….. ………………………………………..
3
Based on the thermochemistry equation table above (no 6, 7 and 8) a. How many moles of substance that combusted? b. What is the sign of enthalpy change of thermochemistry no. 6, 7 and 8?
a. ………………………………………… ……………………………………….. b. ……………………………………….. ………………………………………..
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c. What is standard enthalpy of combustion? 4
5
6
Based on the thermochemistry equation table above (no 9 and 10) a. How many moles of substance that atomized into their atoms? b. What is the sign of enthalpy change of thermo chemistry no 9 and 10? c. What is standard enthalpy of atomization? Based on the thermochemistry equation table above (no 11 and 12) a. How many moles of substance that dissolved into the solvent? b. What is standard enthalpy of solution?
Based on the thermochemistry equation table above (no 13 and 14) a. How many moles of water that produced at the process? b. What is the sign of enthalpy change of thermo chemistry no 13 and 14? c. What is standard enthalpy of neutralization?
Thermochemistry/sman3malang/;by m. hariyanto
c. ……………………………………….. ………………………………………..
a. ………………………………………… ……………………………………….. b. ……………………………………….. ……………………………………….. c. ……………………………………….. ………………………………………..
a. ………………………………………… ……………………………………….. b. ……………………………………….. ………………………………………..
a. ………………………………………… ……………………………………….. b. ……………………………………….. ……………………………………….. c. ……………………………………….. ………………………………………..
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3) Conclude the definition of each type of reaction/process by completing the following table! No 1
Type of Enthalpy Change
General Equation
Standard enthalpy of fusion (∆ H
2
Definition
0 fus
X(s) → X(l)
∆H=+x kJ
)
Standard enthalpy of 0
vaporization (∆ H vap )
3
Standard enthalpy of 0
sublimation (∆ H sub )
4
Standard enthalpy of
Element X + element Y → Compound XY ∆H=+/- x kJ
0 f
formation (∆ H )
5
Standard enthalpy of 0
combustion (∆ H c )
6
Standard enthalpy of 0
atomization (∆ H a )
7
Standard enthalpy of 0
solution (∆ H sol )
8
Standard enthalpy of neutralization 0
(∆ H neut )
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01.
What is the type of the following process? a. I2(s) → I2(g) b. MgC2(s) → MgC2(aq) c. C12H22O11(s) + 11O2(g) → 12CO2(g) + 11H2O(l) d. ½ N2(g) + 2H2(g) + ½ Cl2(g) → NH4Cl(s) e. 2HCl(aq) + Ca(OH)2(aq) → CaCl2(aq) + 2H2O(l)
02.
Write the thermochemistry equation of formation, if given the following data: a. ∆ H 0f C6H12O6(s) = -1260 kJ/mol b. ∆ H 0f Fe2O3(s) = -822 kJ/mol c. ∆ H 0f HBr(g) = -36.4 kJ/mol d. ∆ H 0f of nitrogen monoxide gas = +90.4 kJ/mol
03.
Write the thermochemistry equation of combustion, if given the following data: a. ∆ H c0 C6H12O6(s) = -2803 kJ/mol b. ∆ H c0 C(graphite) = -393.505 kJ/mol c. ∆ H c0 of Hydrogen gas = -286 kJ/mol d. ∆ H c0 B2H6(g) = -2035 kJ/mol
Thermochemistry/sman3malang/;by m. hariyanto
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04.
Write the thermochemistry equation of atomization, if given the following data: a. ∆ H a0 HCl(g) = +428.02 kJ/mol b. ∆ H a0 CH4 (g) = +1656 kJ/mol c. ∆ H a0 H2O(g) = +1856 kJ/mol d. ∆ H a0 NH3(g) = +1167 kJ/mol
05.
Write the thermochemistry equation of solution, if given the following data: 0 CaSO4(s) = -17.8 kJ/mol a. ∆ H sol 0 KNO3(s) = +34.9 kJ/mol b. ∆ H sol
06.
Write the thermochemistry equation of neutralization for aqueous solution Hydrochloric acid and aqueous solution of ammonia if given their standard of neutralization is -52.2 kJ/mole.
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07.
Given the standard enthalpy of solution of sodium hydroxide solid is -43 kJ/mol. Calculate the heat that released/absorbed for dissolving 800 grams of sodium hydroxide in the water.
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3rd worksheet MEASUREMENT OF ENTHALPY CHANGE FOR A REACTION BY EXPERIMENT
Drs. M. Hariyanto SMA Negeri 3 Malang (State Senior High School) Jl. Sultan Agung Utara No 7 Phone (0341) 324 768 Malang 65111 (website : http://psb-sman3malang.com )
There are five way to determine or calculate enthalpy change for a reaction, that is experiment/calorimetric, Hess’ Law, use data of standard enthalpy of formation (∆ H 0f ), use data of standard enthalpy of combustion (∆ H c0 ), and use data of standard enthalpy of atomization (∆ H a0 ) or Energy bonding (D). The following activity will determine enthalpy change for a reaction by experiment or calorimetry.
Before we determine or calculate the enthalpy change by calorimetric, all of you have to understand the relationship between heat (Q) and temperature change (∆T) 1. Information a. Calorimetry Calorimetry is measuring heat based on observing the temperature change when a body absorbs or releases energy as heat. The device used experimentally to determine the heat associated with chemical reaction is called calorimeter.
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Calorimeter 1) The relationship between heat (Q) and temperature change (∆T) Q = m.c. ∆T Q = C. ∆T
Q = heat (Joule) m = mass (g) c = specific heat capacity (J.K-1.g-1) C = heat capacity (J.K-1) ∆T = temperature change (K or ˚C)
2) Calculate heat of reaction by calorimetry Based on conservation energy law:
QABSORBED + QRELEASED = 0 If reaction/system releases heat, so surroundings (solution/water and calorimeter) absorb heat.
QCALORIMETER + QSOLUTION + QREACTION = 0 QREACTION = - (QCALORIMETER + QSOLUTION) NOTE: QCALORIMETER = CCALOIMETER. ∆T QSOLUTION = mSOLUTION.cSOLUTION. ∆T
Measurement of Enthalpy Change by Experiment Purposes Students are able to measure the enthalpy of reaction
Equipments and materials No 1 2 3 4 5 6 7
Equipments/materials Thermometer Graduated cylinder Polystyrene cup Glass container Glass stirring rod HCl solution NaOH solution
Capacity -10 to 100˚C 100 mL 1M 1M
Thermochemistry/sman3malang/;by m. hariyanto
Number 1 2 1 1 1 50 mL 50 mL
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Procedure (1) Place 50 mL of HCl solution into a polystyrene cup and measure its temperature. Place the cup a glass container (2) Measure 50 mL of 1M NaOH solution into a graduated cylinder and meausure its temperature (3) Mix the NaOH solution to HCl solution, stir briefly with a glass stirring rod, and note the maximum temperature reached.
Assignments (1) Record the data observation Initial Temperature HCl NaOH Average
Final Temperature
Temperature Change
(2) By assuming the head absorbed by the cup and the heat losses to the air are negligible, calculate the amount of energy released and calculate heat of reaction (QREACTION). The heat released is the heat of neutralization of 50 mL of 1M of HCl solution and 50 mL of 1M of NaOH solution.
(3) Calculate the enthalpy change per mole of water (H2O) that produced by reaction of 1 M of HCl solution and 1M of NaOH solution
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(4) Write the thermochemistry equation!
(5) What is the type of the enthalpy change?
01.
500 mL of 1M of nitric acid solution is mixed to 500 mL of 1M of potassium hydroxide solution. The temperature increases 7.5˚C, given the specific heat capacity of water is 4.20 J. ˚C-1.g-1. Calculate: a. calculate heat of reaction b. calculate the enthalpy of neutralization of nitric acid solution and potassium hydroxide solution c. write the thermal equation
02.
Given the enthalpy of combustion of carbon is -418 kJ/mol. How many grams of carbon to boil 500 mL of water at 25˚C; 1 atmospheric pressure. Given specific heat capacity of water is 4.18 J.K.g-1.
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4th worksheet HESS’ LAW Drs. M. Hariyanto SMA Negeri 3 Malang (State Senior High School) Jl. Sultan Agung Utara No 7 Phone (0341) 324 768 Malang 65111 (website : http://psb-sman3malang.com )
There are five way to determine or calculate enthalpy change for a reaction, that is experiment/calorimetric, Hess’ Law, use data of standard enthalpy of formation (∆ H 0f ), use data of standard enthalpy of combustion (∆ H c0 ), and use data of standard enthalpy of atomization (∆ H a0 ) or Energy bonding (D). The following activity will determine enthalpy change for a reaction by Hess’ Law.
Before we determine or calculate the enthalpy change by Hess’ Law, it is necessary to review the previous material, that is the characteristics of enthalpy change and diagram of energy level. 1. Answer the following questions! No Questions 1 Given thermochemistry equation:
Answer a. ………………………………………..
0
C(graphite) + O2(g) → CO2(g) ∆ H =-394 kJ
a. determine enthalpy change for formation of 2.2 g of carbon dioxide gas from graphite and oxygen gas b. determine enthalpy change for decomposition of 11 g of carbon dioxide gas into graphite and oxygen gas 2
Given thermochemistry equation:
b. ………………………………………..
a. …………………………………… 0
II. N2(g) + 2O2(g) → 2NO2(g) ∆ H =+68 kJ 0
III. O2(g) + 2NO(g) → 2NO2(g) ∆ H =-112 kJ
Draw the diagram of energy level of: a. reaction I
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b. reaction II
b. ……………………………………..
c. by combining the diagram of energy level of reaction I and reaction II, calculate ∆ H 0 of:
c. ……………………………………..
N2(g) + O2(g) → 2NO(g)
Hess’ Law Purposes Students are able to 1. understand Hess’ Law 2. use Hess’ Law to determine enthalpy change for q reaction
Information State function In thermodynamics, a state function, state quantity, or a function of state, is a property of a system that depends only on the current state of the system, not on the way in which the system acquired that state. A state function describes the equilibrium state of a system. For example, potential energy, internal energy, enthalpy and entropy are state quantities because they describe quantitatively an equilibrium state of thermodynamic systems.
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Assignment 1) Observe and complete the following table! No
1
Process
Diagram of Energy Level
Energy Cycle
Student is standing at the first floor. She are going to reach third floor through two route: Route I: Student reaches the third floor by stepping on the stairs through the second floor, and the third floor Route II: Student reaches the third floor directly by lift.
1stfloor →3rdfloor ∆Ep3
Route II: C(s) + O2(g) →CO2(g) ∆H3=-394kJ
Enthalpy (H)
Carbon dioxide gas is formatted from carbon and oxygen by two route: Route I: C(s) + ½ O2(g)→CO(g) ∆H1=-111kJ CO(g)+ ½ O2(g)→CO2(g) ∆H2=283kJ
Relationship among the energies
1stfloor →2ndfloor ∆Ep1 2ndfloor →3rdfloor ∆Ep2
The height of the second floor is 3 m and the height of third floor is 6 m from the first floor.
2
The Sum of Process/Reaction
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∆Ep3 = ∆Ep1 + ∆Ep2 +
2) Based on the data above, answer the following questions! No Questions 1 a. Compare the magnitude of potential energy change (process 1) for route I (one step)and route II ( two step), is it the same or different? b. Based on the answer of question 1a, does the magnitude of potential change depend on the pathway of process? c. Conclude the magnitude of potential energy of one step process and a series steps of process. 2
Answer
a. Compare the magnitude of enthalpy change (process 2) for route I (one step)and route II ( two step), is it the same or different? b. Based on the answer of question 2a, does the magnitude of enthalpy change depend on the pathway of process? c. Conclude the magnitude of enthalpy change of one step process and a series steps of process.
Conclusion The answer of assignment no 2c is the expression of Hess’ Law, conclude it! HESS’ LAW The magnitude of enthalpy change in going on from some initial state (a particular set of reactants) to some final state ( a particular of products) is dependent/independent*) of the pathway, the enthalpy change is the same/different*) whether the reaction take place in one step or in a series of steps.
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01. Given the thermal equation: N2(g) + O2(g) → 2NO(g) ∆H=180 kJ 2NO(g) + O2(g) → 2NO2(g) ∆H=-112 kJ Calculate the enthalpy change of reaction N2(g) + O2(g) → 2NO2(g) by the following methods: a. diagram of energy level b. energy cycles c. summing of reactions
02. Given the thermal equation: C(graphite) + O2(g) → CO2(g) ∆H=-394 kJ C(diamond) + O2(g) → CO2(g) ∆H=-396 kJ Calculate the enthalpy change of reaction C(graphite) → C(diamond) by the following methods: a. diagram of energy level b. energy cycles c. summing of reactions
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03. Given the following equation: ∆H=-822 kJ 2Fe(s) + 3/2 O2(g) → Fe2O3(s) ∆H=-110.5 kJ C(graphite) + O2(g) → CO2(g) Determine enthalpy change of the following reaction (by method of energy cycle and summing reactions): Fe2O3(s) + 3C(graphite) → 2Fe(s)+ CO2(g)
04. Given the following data: ∆H=-394 kJ (a) C(s) + O2(g) → CO2(g) (b) C3H4(g) + 4O2 (g) → 3CO2(g) + 2H2O(l) ∆H=-1938 kJ ∆H=-286 kJ (c) H2(g) + ½ O2(g) → H2O(l) Calculate ∆H for the synthesis of propyne (C3H4) from its elements, according to the equation by method of energy cycle and summing the reactions 3C(s) + 2H2(g) → C3H4(g)
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05. Given the following data: ∆H=-283 kJ (a) CO(g) + ½ O2(g) → CO2(g) ∆H=-286 kJ (b) H2(g) + ½ O2(g) → H2O(l) (c) CH3OH(l)+ 3/2 O2(g)→ CO2(g)+2H2O(l) ∆H=-715 kJ Calculate ∆H for the following reaction by method of summing the reactions CO(g) + 2H2(g) → CH3OH(l)
06. Given the following data: ∆H=-1273 kJ (a) 2B(s) + 3/2 O2(g) → B2O3(s) (b) B2H6(g) + 3O2 (g) → B2O3(s) + 3H2O(g) ∆H=-2035 kJ ∆H=-286 kJ (c) H2(g) + ½ O2(g) → H2O(l) ∆H=+44 kJ (d) H2O(l)→ H2O(g) Calculate ∆H for the synthesis of diborane (B2H6) from its elements, according to the equation by method of summing the reactions 2B(s) + 3H2(g) → B2H6(g)
07. Given the following data: ∆H=-102 kJ PH3(g) + HI(g) → PH4I(s) ∆H=+5.4kJ P(s) + 3/2 H2(g) → PH3(g) ∆H=+53kJ H2(g) + I2(g) → 2HI(g) Calculate the heat released/absorbed for formation of 8.1 g of PH4I (Mr=162).
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Additional Notes
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5th worksheet CALCULATION ENTHALPY CHANGE FOR A REACTION BASED ON: 9 THE DATA OF STANDARD ENTHALPY OF FORMATION 9 THE DATA OF STANDARD ENTHALPY OF COMBUSTION 9 THE DATA OF STANDARD ENTHALPY OF ATOMIZATION/BONDING ENERGY
Drs. M. Hariyanto SMA Negeri 3 Malang (State Senior High School) Jl. Sultan Agung Utara No 7 Phone (0341) 324 768 Malang 65111 (website : http://psb-sman3malang.com )
Enthalpy change for a reaction can be determined by experiment/calorimetric, Hess’ Law, based on the data of standard enthalpy of formation, based on the data of standard enthalpy of combustion, based on the data of bonding energy. The following activities are the three way to calculate enthalpy change for a reaction.
CALCULATION ∆HREACTION BASED ON THE DATA OF ∆Hf Purposes Students are able to calculate the enthalpy change for a reaction based on the data of standard enthalpy of formation
Assignments 1) Read and complete the following table based on the previous material of Hess’ energy cycle
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No
1
2
Process
The reactants react each other to produce the products accompanied by ∆Hreaction. Each reactant is formed from its elements accompanied by ∆Hf REACTANT and each product is formed from its elements by accompanied by ∆Hf PRODUCT 1. Draw the direction of arrow at energy cycle 2. write the relationship among ∆Hreaction, ∆Hf REACTANT, and ∆Hf PRODUCT Propyne gas (C3H4) is combusted to produce carbon dioxide gas (CO2) and water (H2O) accompanied by ∆Hreaction. C3H4(g), CO2(g), and H2O(l) are formed from their elements, C(s), H2(g), and O2(g) accompanied by ∆Hf C3H4(g), ∆Hf CO2(g), and ∆Hf H2O(l)
Thermochemistry/sman3malang/;by m. hariyanto
Hess’ Energy Cycle
∆Hreaction
Reactants
Products
Relationship among the enthalpy change
∆Hreaction=……………………………..
∆Hf PRODUCT
∆Hf REACTANT Elements
∆Hreaction
C3H4(g) + 4O2 (g) → 3CO2(g) + 2H2O(l) ∆Hf C3H4(g)
3.∆Hf CO2(g) 2.∆Hf H2O (l)
C(s) + 2H2(g) + 4O2(g)
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∆Hreaction=……………………………..
2) Conclude! What is the relationship among enthalpy change of reaction (∆Hreaction), the sum of standard enthalpy of formation of reactants (∑∆Hf of reactants), and the sum of standard enthalpy of formation of products (∑∆Hf of products)
Additional Notes
CALCULATION ∆HREACTION BASED ON THE DATA OF ∆HC Purposes Students are able to calculate the enthalpy change for a reaction based on the data of standard enthalpy of combustion
Assignments 1) Read and complete the following table based on the previous material of Hess’ energy cycle
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No
1
2
Process
The reactants react each other to produce the products accompanied by ∆Hreaction. Each reactant is combusted to produce the product of combustion accompanied by ∆Hc REACTANT and each product also is combusted to produce the products of combustion by accompanied by ∆Hc PRODUCT 1. Draw the direction of arrow at energy cycle 2. write the relationship among ∆Hreaction, ∆Hc REACTANT, and ∆Hc PRODUCT Propyne gas (C3H4) is formed from its elements, C(s) and H2(g) accompanied by ∆Hreaction. C(s), H2(g), and C3H4(g) are combusted to produce carbon dioxide gas (CO2) and water (H2O) accompanied by ∆Hc C(s), ∆Hc H2(g), and ∆Hc C3H4(g).
Hess’ Energy Cycle
∆Hreaction
Reactants
∆Hc
Products
∆Hreaction=……………………………..
∆Hc PRODUCT
REACTANT
Products of combustion
3C(s)
+ 2H2 (g)
∆Hreaction
→
3.∆Hc C(s) 2.∆Hc H2(g)
3CO2(g) + 2H2O(l)
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Relationship among the enthalpy change
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C3H4(g) ∆HcC3H4(g)
∆Hreaction=……………………………..
2) Conclude! What is the relationship among enthalpy change of reaction (∆Hreaction), the sum of standard enthalpy of combustion of reactants (∑∆Hc of reactants), and the sum of standard enthalpy of combustion of products (∑∆Hc of products)
Additional Notes
CALCULATION ∆HREACTION BASED ON THE DATA OF ∆Ha or Bonding Energy Purposes Students are able to calculate the enthalpy change for a reaction based on the data of bonding energy
Pre-knowledge Before to use data of bonding energy to calculate the enthalpy change for a reaction, we are going to review how to draw the structure formula or displayed formula, because it show the number and type of covalent bonding.
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Answer the following questions! No Questions 1 Draw the structure formula for the following substance and how many bonds of each type of bonding? a. H2 b. H2S c. NH3 d. C2H6 e. C2H4 f. C2H2
Answer
Information 1. Bonding energy of diatomic molecule Bonding energy is the amount of energy required to break one mole of bond in gaseous phase of covalent substance to form product in the gaseous phase at constant temperature and pressure. So bonding energy of diatomic molecule is the same with enthalpy of atomization. Example: Enthalpy atomization (∆Ha) of F2(g)= +159 kJ/mol, so the thermochemistry equation is: F2(g) → 2F(g) ∆H=+159 kJ or F-F(g) → 2F(g) ∆H=+159 kJ Bonding energy of F-F in F2 (DF-F)=+159 kJ For diatomic molecule: Bonding Energy (D) = Enthalpy of atomization (∆Ha) 2. Bonding energy of polyatomic molecule Bonding energy is the average of enthalpy of atomization for a number of different species (molecules or ions) containing particular bonding. Example: Enthalpy atomization (∆Ha) of H2O(g)= +926.7 kJ/mol, so the thermochemistry equation is: → 2H(g) + O(g) ∆H=+926.7 kJ Or H-O-H(g) → 2H(g) + O(g) ∆H=+926.7 kJ H2O(g) The number of O-H bond in per mole of H2O is two moles, so Bonding energy of O-H=
926.7kJ =463.4 kJ/mole 2 moles
For polyatomic molecules: Bonding Energy (D) =
Enthalpy of atomization number of mole of bond
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Assignments 1) Read and complete the following table based on the previous material of Hess’ energy cycle No
1
2
Process
The reactants react each other to produce the products accompanied by ∆Hreaction. Each reactant is atomized to produce their atoms accompanied by ∆Ha REACTANT or ∑DREACYANT and each product also is atomized to produce their by accompanied by ∆Ha PRODUCT or ∑DPRODUCT a. Draw the direction of arrow at energy cycle b. write the relationship among ∆Hreaction, D REACTANT, and DPRODUCT Propene gas (C3H4) is hydrogenised to produce Propyne gas (C3H4) accompanied by ∆Hreaction. C3H4(g), H2(g), and C3H4(g) are atomized to produce their atoms, C(g) and H(g) accompanied by ∆Ha C3H4(g), ∆Ha H2(g), and ∆Ha C3H4(g). ∆Ha C3H6=1.DC=C+1.DC-C+6.DC-H ∆Ha C3H4=1.DC≡C+1.DC-C+4.DC-H ∆Ha H2=1.DH-H
Thermochemistry/sman3malang/;by m. hariyanto
Hess’ Energy Cycle
∆Hreaction
Reactants
Products
Relationship among the enthalpy change
∆Hreaction=……………………………..
∑D PRODUCT
∑DREACTANT Atoms
C3H4(g)
∆Hreaction
+ H2 (g)
∆Ha C3H4
→
∆Ha H2
C3H6(g) ∆HaC3H6
3Cg)+ 6H(g)
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∆Hreaction=……………………………..
2) Conclude! What is the relationship among enthalpy change of reaction (∆Hreaction), the sum of bonding energy of reactants (∑D of reactants), and the sum of bonding energy of products (∑D of products)
Additional Notes
01. Calculate enthalpy change of the following reaction: 3C(s) + F2O3(s) → 2Fe(s) + 3CO(g) Given: ∆Hf F2O3(s)= -822 kJ/mole ∆Hf CO(g) = -110 kJ/mole
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02. The lunar module which landed the first man on the Moon in 1969 used methylhydrazine, CH3NHNH2, and dinitrogen tetraoxide as propellants. The equation reaction in the engine is given as follows: 4CH3NHNH2(l) + 5N2O4(l) → 4CO2(g) + 9N2(g) + 12H2O(l) Calculate enthalpy change of reaction if the appropriate enthalpy changes of formation are given below: CH3NHNH2(l) = +53kJ/mole =-20kJ/mole N2O4(l) =-394kJ/mole CO2(g) =-285kJ/mole H2O(l)
03. Given standard enthalpy of combustion for some substances: ∆Hc C(s) = -394kJ/mole ∆Hc H2(g) = -286kJ/mole ∆Hc C3H4(g)= -1938kJ/mole Calculate standard enthalpy of formation for propyne (C3H4)
04. Changing 2 mole of C(graphite) to C(diamond) need 2 kJ of heat. Calculate standard enthalpy of combustion of C(diamond) if given standard enthalpy of combustion of C(graphite) is 396kJ/mole.
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05. Calculate the heat released by combustion of 5.6 g ethylene, C2H4 gas if he appropriate of bonding energies are given below: DC=C = + 611kJ/mole DO=O = +498kJ/mole DC=O = +736kJ/mole DH-O = +464kJ/mole
06. Given the following data: = + 946kJ/mole DN≡N = +436kJ/mole DH-H ∆Hf NH3(g)= -46kJ/mole Calculate the bonding energy of N-H in ammonia gas.
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Before we study about Thermochemistry, we should review the previous material: substances that involved in reaction, what is relationship between number of moles of substances in reaction and coefficient, physical states of substance, the evidences of chemical reaction, and units of energy and heat. Answer the following questions! No Questions 1 Identify, which substances that called reactants and products in the following reaction: Ca(OH)2(aq)+2HCl(aq) →CaCl2(aq) +2H2O(l) 2 a. Balance the following reaction: ..(NH4)2SO4(aq)+.. KOH(aq) →.. K2SO4(aq)+ …H2O(l)+ .. NH3(g) b. Write the proportional of number of moles of each substance! c. If 2 moles of ammonium sulfate react with 2 moles of potassium hydroxide, how many moles of potassium sulfate and ammonia gas that produced?
Answer Reactants: ………………………….. Products :…………………………… a. …………………………………… b. …………………………………….. c. ……………………………………..
3
Mention the physical states that you knew before!
………………………………………….. …………………………………………..
4
How to write the chemical formula of the following substances: a. Hydrogen gas b. Oxygen gas c. Nitrogen gas d. Fluorine gas e. Chlorine gas f. Bromine liquid g. Iodine solid
………………….. ………………….. ………………….. ………………….. ………………….. ………………….. …………………..
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h. i. j. k. l.
4
5
Phosphorus Sulfur Iron Carbon Glucose that consists of 6 atoms of C, 12 atoms of H, and 6 atoms of O per molecule m. Barium phosphate n. Aluminum sulfate Give the evidences or phenomena that accompany the chemical reaction What is heat? What is the unit of heat?
………………….. ………………………. ………………………. ………………………. ................... ………………………. ………………………. ……………………………………………….. ………………………………………….. ………………………………………….. ………………………………………….. ………………………………………….. …………………………………………..
System and Surrounding Purposes
Students are able to: Identify the system and the surroundings for chemical reactions.
Assignment
Observe the following figure and complete the blank! Cases Figures System Student is observing Aqueous solution of aqueous solution of sodium hydroxide Sodium hydroxide in test-tube
Teacher is observing mixture of aqueous solutions of silver nitrate and hydrochloric acid aqueous solution react to produce silver chloride solid and nitric acid aqueous solution in Erlenmeyer-flask
Surrounding -Test-tube -space outside of test-tube
……………………..
………………………
……………………..
………………………
………………………
………………………
……………………..
……………………..
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Conclusion
Based on your observation of the cases above, conclude and describe the definition of system and surrounding!
Exothermic and Endothermic Reaction Based on heat or energy that accompany (absorbed or released by) the system, chemical reaction classified into 2 (two) types), that is exothermic and endothermic reaction. Heat or energy moves/flows from system to the surroundings or the other around way. How heat for chemical reactions can be expressed? What is exothermic reaction? What is endothermic reaction? To answer the questions above, please do the activity below!
Purposes
Students are able to: 1. describe how heat for chemical reactions can be expressed as the change of enthalpy, ∆H 2. Identify the characteristics of exothermic and endothermic reactions.
Information of Enthalpy,H and Enthalpy Change, ∆H
1. Enthalpy (H) or heat content is chemical energy stored within a substance is a type of potential energy. 2. Enthalpy change (∆H) is the amount of heat released or absorbed by system at constant pressure. Enthalpy change of chemical reaction can be expressed as follows: ∆H = Hproducts - Hreactants 3. The value of enthalpy change, ∆H depend on the amount of enthalpy of reactants and enthalpy of products. If enthalpy of products is more than enthalpy of reactants, the value of ∆H is positive, the system absorbed heat from the surrounding. In the other way, if enthalpy of product is less than enthalpy of reactant, the value of ∆H is negative, the system release heat to the surrounding.
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Experiment of exothermic and endothermic reaction a. Equipments and materials No Equipments/materials 1 Thermometer 2 Glass beaker 3 Plastic teaspoon 4 NaOH solid 5 NaCl solid 6 NH4Cl solid 7 Distilled water
Capacity -10 to 100˚C 100 mL -
Number 1 3 3 1.5 teaspoon 1.5 teaspoon 1.5 teaspoon 50 mL
b. Procedure 1) Place about 15 mL of distilled water in a 100 mL glass beaker and measure its temperature. Add one half of teaspoon of sodium hydroxide solid, stir gently, and record any change in temperature. 2) Repeat procedure 1) using one half of teaspoon of ammonium chloride 3) Repeat procedure 1) using one half of teaspoon of sodium chloride c. Data observation Experiment 1 2 3
Solute ………….. ………….. …………..
Solvent ………….. ………….. …………..
Initial temperature ………….. ………….. …………..
Final Type of temperature process ………….. ………….. ………….. ………….. ………….. …………..
NOTE: 1. Type of process is exothermic reaction, if final temperature is more than initial temperature 2. Type of process is endothermic reaction, if final temperature is less than initial temperature d. Assignment Based on the data above, answer the following questions No Questions Answer 1 The system releases heat to the ……………………………………………………………… surroundings if final temperature is more than initial temperature. …………………………………………………………….. What is the type of process? 2 The system absorbs heat from the ……………………………………………………………… surroundings if final temperature is less than initial temperature. …………………………………………………………….. What is the type of process? 3 Based on the answers of questions ……………………………………………………………… no 1, a. which experiment that called …………………………………………………………….. exothermic reaction?
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b. which experiment that called endothermic reaction? 4
What do you think of the value of enthalpy change of a. exothermic reaction? b. Endothermic change?
……………………………………………………………… ……………………………………………………………..
e. Conclusion Conclude the characteristic of each type of process (exothermic and endothermic) about flowing of heat, amount of enthalpy of system and surroundings (or product and reactant), and the value of enthalpy change!
Additional Notes
Thermochemistry/sman3malang/;by m. hariyanto
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Thermochemistry Equation and Characteristics of Enthalpy Change After understanding the enthalpy, enthalpy change, and characteristics of exothermic reaction and endothermic reaction, now how to express the equation of reaction with energy/heat that accompany? And what are the characteristics of enthalpy change? To answer them, do the following activity!
A. THERMOCHEMISTRY EQUATION
Purpose
Students are able to: express/write the thermochemistry equation
Assignment 1. Observe and complete the following table No 1
2
3
4
5
Process 0.5 moles of nitrogen gas with 1.5 moles of hydrogen gas react to produce 1 mole of ammonia gas by releasing 46 kJ of heat 1 mole of nitrogen gas with 3 moles of hydrogen gas react to produce 2 mole of ammonia gas by releasing 92 kJ of heat 2 mole of carbon solid with 1 mole of hydrogen gas react to produce 1 mole of acetylene (C2H2) gas by absorbing 227 kJ of heat 4 mole of carbon solid with 2 moles of hydrogen gas react to produce 2 moles of acetylene (C2H2) gas by absorbing 554 kJ of heat 1 mole of carbon solid with 2 moles of hydrogen gas react to produce 1 mole of methane (CH4) gas by releasing 75 kJ of heat
Thermochemistry Equation 0.5 N2(g) + 3/2 H2(g) → NH3(g) ∆H=-46 kJ
N2(g) + 3 H2(g) → 2NH3(g)
2C(s) + H2(g) → C2H2(g)
∆H=-92 kJ
∆H=+227 kJ
…………………………………………………………………
…………………………………………………………………
Thermochemistry/sman3malang/;by m. hariyanto
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6
7
8
3 moles of carbon solid with 6 moles of hydrogen gas react to produce 3 mole of methane (CH4) gas by releasing … kJ of heat 2 moles of carbon solid, 3 moles of hydrogen gas, and 0.5 moles of oxygen gas react to produce 1 mole of ethanol (C2H5OH ) liquid by releasing 278 kJ of heat 1 mole of carbon solid, 1.5 moles of hydrogen gas, and 0.25 moles of oxygen gas react to produce 0.5 moles of ethanol (C2H5OH ) liquid by releasing … kJ of heat
…………………………………………………………………
…………………………………………………………………
…………………………………………………………………
2. Answer the following questions No 1
Question Please observe the process and their thermochemistry equation above. Identify what anything that thermochemistry equation) described/shown?
Answer ………………………………………………………. ………………………………………………………. ………………………………………………………. ………………………………………………………. ……………………………………………………….
Conclusion Based on the answer of question above, describe the definition of thermochemistry equation!
B. THE CHARACTERISTICS OF ENTHALPY CHANGE
Purpose
Students are able to: describe the characteristics of enthalpy change
Thermochemistry/sman3malang/;by m. hariyanto
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Assignment 1. Observe and complete the following table a. The relationship between enthalpy change and number of mole of substance No Process Thermochemistry Equation 1 2 moles of carbon solid, 3 moles of hydrogen gas, and 0.5 moles ………………………………………………………………… of oxygen gas react to produce 1 mole of ethanol (C2H5OH ) liquid by releasing 278 kJ of heat 2 1 mole of carbon solid, 1.5 moles of hydrogen gas, and 0.25 ………………………………………………………………… moles of oxygen gas react to produce 0.5 moles of ethanol (C2H5OH ) liquid by releasing … kJ of heat
No 1
2
b. The relationship between enthalpy change and direction of reaction Process Thermochemistry Equation 0.5 moles of nitrogen gas with 1.5 moles of hydrogen gas react ………………………………………………………………… to produce 1 mole of ammonia gas by releasing 46 kJ of heat 1 mole of ammonia gas decomposes to produce 0.5 ………………………………………………………………… moles of nitrogen gas with 1.5 moles of hydrogen gas by absorbing 46 kJ of heat
c. The relationship between enthalpy change of some reactions and enthalpy change of total reaction No Process Thermochemistry Equation 1 Reaction I 1 mole of nitrogen gas and 1 mole ………………………………………………………………… of oxygen gas react to produce 2 mole of nitrogen monoxide by absorbing 180 kJ of heat 2 Reaction II 2 moles of nitrogen monoxide gas ………………………………………………………………… and 1 mole of oxygen gas react to produce 2 mole of nitrogen dioxide by releasing 112 kJ of heat
Thermochemistry/sman3malang/;by m. hariyanto
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3
Reaction III 1 moles of nitrogen gas and 2 mole of oxygen gas react to produce 2 mole of nitrogen dioxide by absorbing 68 kJ of heat
Reaction I :………………………………………………… Reaction II :…………………………………………………+ Reaction III:………………………………………………..
2. Answer the following questions No 1 2 3
Questions What is the relationship between enthalpy change and number of mole of substance in thermochemistry equation? What is the relationship between enthalpy change and direction of reaction in thermochemistry equation? What is the relationship between enthalpy change of some reactions and enthalpy change of total reaction in thermochemistry equation?
Answer …………………………………………………. …………………………………………………. ………………………………………………….
Conclusion
01. Identify the systems and the surroundings for: a. mixture of aqueous solution of barium nitrate and aqueous solution of sulfuric acid that placed in the glass beaker b. mixture of aqueous solution of Lead(II) nitrate and aqueous solution of sodium iodide that placed in the test tube c. reaction of nitrogen gas and oxygen gas to produce nitrogen monoxide in the air
Thermochemistry/sman3malang/;by m. hariyanto
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02. Identify the following process are endothermic or exothermic reaction! a. reaction of aqueous solution of sodium hydroxide and aqueous solution of hydrochloric acid in test tube so temperature of test tube wall increases 10˚C b. combustion of methane gas to produce 888 kJ of heat c. dissolving of urea in the water in test tube so the temperature of test tube is decreasing d. N2(g) + 2O2(g) → 2NO(g) – 68 kJ e. C(graphite) + O2 → CO2(g) ∆H=-393.5 kJ f. Given the diagram of energy of carbon disulfide formation below: H 4CS2(g) Product 4C(s)+ S8(v) Ractants
03. Write the thermochemistry equation of the following process! a. 1 mole of hydrogen gas and 0.5 moles of oxygen gas react to produce vapor of water by releasing 285.8 kJ of heat. b. 2 moles of carbon solid and 2 mole of hydrogen gas react to give 1 moles of ethylene (C2H4) gas by absorbing 52 kJ of heat.
04. Given: 2H2(g) + O2(g) → 2H2O(l) ∆H=-571.6 kJ a. Calculate the heat that released by formation of 1 mole of water vapor b. Calculate the heat that released by formation of 9 grams of water vapor c. Calculate the heat that released by decomposition of 1 mole of water vapor to produce hydrogen gas and oxygen gas
Thermochemistry/sman3malang/;by m. hariyanto
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d. Calculate the heat that released by decomposition of 3.6 grams of water vapor to produce hydrogen gas and oxygen gas.
05. Given: Reaction I : C(graphite) + ½ O2(g) → CO(g) ∆H=-110.5 kJ ∆H=-282 kJ Reaction II : CO(g) + ½ O2(g) → CO2(g) Calculate enthalpy change of the following reaction: C(graphite) + O2(g) → CO2(g)
Thermochemistry/sman3malang/;by m. hariyanto
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2nd worksheet TYPE OF ENTHALPY CHANGE Drs. M. Hariyanto SMA Negeri 3 Malang (State Senior High School) Jl. Sultan Agung Utara No 7 Phone (0341) 324 768 Malang 65111 (website : http://psb-sman3malang.com )
We should review the previous material: exothermic and endothermic reaction, thermochemistry equation, and characteristics of enthalpy change. We also study the type of reaction before. How many types of enthalpy change? How to determine the magnitude of each enthalpy change? Answer the following questions! No Questions Given: H2(g) +1/2 O2(g)→2H2O(l) ∆H=-235.8 kJ T
a. Identify the reaction above is exothermic or endothermic. b. Calculate the heat that released/absorbed by formation of 3.6 g of water vapor c. Calculate the heat that released/absorbed by decomposition of 4.5 grams of water vapor
2
What factors that determine the value and magnitude of enthalpy change? (Please answer based on the activity 3b worksheet 1)
Answer 1. ………………………………………… 2. ……………………………………….. ……………………………………….. ……………………………………….. 3. ……………………………………….. ……………………………………….. ……………………………………….. …………………………………… .………………………………….. …………………………………… .…………………………………..
Information
Standard Enthalpy Change (∆H˚) Standard enthalpy change is symbolized by ∆H˚ (delta H degree or delta H zero). Standard enthalpy change is measured at standard state 1. For compound - The standard state of a gaseous substance is pressure of exactly 1 atmosphere - The standard state of a substance present in a solution, standard state is a concentration of exactly 1 M - The standard state of pure substance in a condensed state (liquid or solid), standard state is the pure or liquid 2. For element - The standard state of an element is the form in which the element exists under condition of 1 atmosphere and 25˚C.
Thermochemistry/sman3malang/;by m. hariyanto
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Type of Reaction Purposes
Students are able to: Identify the type of chemical reactions.
Assignments
1) Observe the following reactions (Please do at your home before doing activity 2) a) Physical Change No Process Type of Process 1 H2O(s) → H2O(l) Melting 2 H2O(l) → H2O(g) Evaporation 3 H2O(s) → H2O(g) Sublimation No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
b) Chemical Change/reaction Reaction C(s) + 2H2(g) → CH4(g) H2(g) +S(s) + 2O2(g) → H2SO4(l) 2Cs) +3H2(g) +1/2 O2(g) → C2H5OH(l) CH4(g) → C(s) + 2H2(g) H2SO4(l) → H2(g) +S(s) + 2O2(g) C2H5OH(l) → 2Cs) +3H2(g) +1/2 O2(g) C(s) + O2(g) → CO2(g) S(s) + O2(g) → SO2(g) CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l) H2(g) → 2H(g) O2(g) → 2O(g) N2(g) → 2N(g) CH4(g) → C(g) + 4H(g) H2O(g) →….. + …….. NaCl(s) → NaCl(aq) C6H12O6(s) → C6H12O6(aq) NaOH(s) → ………… HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq) + 2H2O(l)
Thermochemistry/sman3malang/;by m. hariyanto
Type of Reaction Formation Formation ………………………. Decomposition ………………………. ………………………. Combustion Combustion ……………………… ………………………. Atomization Atomization Atomization Atomization Atomization Dissolving Dissolving Dissolving Neutralization Neutralization
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2) Based on the tables above, answer the following question! No Questions Answer 1 Based on the process at physical change table, observe the physical states of each reactant a. ………………………………………… and product, and the name of process. ……………………………………….. a. What is melting process? b. What is melting evaporation? b. ……………………………………….. c. What is melting sublimation? ……………………………………….. c. ……………………………………….. ……………………………………….. 2
Based on reaction of formation (reaction 1,2, and 3 at table of chemical change above): a. Identify (element or compound) the reactants and products of reactions b. What is formation reaction? Based on reaction of decomposition (reaction 4,5, and 6 at table of chemical change above): a. Identify (element or compound) the reactants and products of reactions b. What is formation decomposition? Based on reaction of combustion (reaction 7,8,9 and 10 at table of chemical change above): a. Identify the element that reacts with substances (C, S, CH4, and C6H12O6) b. What is combustion reaction?
a. …………………………………………….. …………………………………………….. b. …………………………………………….. ……………………………………………..
5
Based on reaction of atomization (reaction 11-15 at table of chemical change above): a. Identify (element or atom) the reactants and products of the reactions! b. What is atomization reaction?
a. …………………………………………….. …………………………………………….. b. …………………………………………….. ……………………………………………..
6
Based on the process at dissolving (reaction 16-18 at chemical change above),: a. Identify the physical states of each reactant and product b. What is dissolving process?
a. …………………………………………….. …………………………………………….. b. …………………………………………….. .…………………………………………..
7
Based on reaction of neutralization (reaction 19-20 at table of chemical change above): c. Identify (acid, base, or salt) the reactants the reactions! d. What is neutralization reaction?
a. …………………………………………….. …………………………………………….. b. …………………………………………….. ……………………………………………..
3
4
Thermochemistry/sman3malang/;by m. hariyanto
a. …………………………………………….. …………………………………………….. b. …………………………………………….. …………………………………………….. a. …………………………………………….. …………………………………………….. b. …………………………………………….. ……………………………………………..
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3) Conclude the definition of each type of reaction/process by completing the following table! No 1
Process/Reaction Melting
2
Evaporation
3
Sublimation
4
Formation
5
Decomposition
6
Combustion
7
Atomization
8
Dissolving
8
Neutralization
Thermochemistry/sman3malang/;by m. hariyanto
Definition
General Equation X(s) → X(l)
Element X + element Y → Compound XY
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Type of Enthalpy Change After understanding the type of process/reaction, the following activity you are going to study about the type of enthalpy change. How many types of enthalpy change in thermochemistry? How to write the equation for each enthalpy change? To answer the questions, please do the following activity!
Purposes
Students are able to: 1. write the equation for the standard enthalpy of formation 2. write the equation for the standard enthalpy of combustion 3. write the equation for the standard enthalpy of atomization 4. write the equation for the standard enthalpy of solution 5. write the equation for the standard enthalpy of neutralization
Assignments
1) Observe and complete the following table! (Enthalpy is measured at 1 atmospheric pressure and 25˚C)
No
Thermochemistry Equation
Type of Process
Type of Enthalpy
1
1H2O(s) → H2O(l) ∆H=+6.02 kJ
………………….
Standard enthalpy of 0
fusion (∆ H fus ) 2
1H2O(l) → H2O(g) ∆H=+41.1 kJ
.………………….
Standard enthalpy of 0
vaporization (∆ H vap ) 3
1H2O(s) → H2O(g) ∆H=+47.12 kJ
.………………….
Standard enthalpy of 0
sublimation (∆ H sub ) 4
C(s) + O2(g) → 1CO2(g) ∆H=-393.5 kJ
.………………….
Standard enthalpy of 0
formation (∆ H f ) 5
2C(s) + H2(g) →1 C2H2(g) ∆H=+226.7 kJ
.………………….
Standard enthalpy of 0
formation (∆ H f ) 6
1C2H6(g) +7/2 O2(g) → 2CO2(g) + 3H2O(l) ∆H=-1560kJ
.………………….
Standard enthalpy of 0
combustion (∆ H c ) 7
1C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l) ∆H=-2220kJ
.………………….
Standard enthalpy of 0
combustion (∆ H c ) 8
1C6H6(g) +15/2 O2(g) → 6CO2(g) + 3H2O(l) ∆H=-3293kJ
.………………….
Standard enthalpy of 0
combustion (∆ H c )
Thermochemistry/sman3malang/;by m. hariyanto
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9
1H2(g) → 2H(g)
∆H=+432 kJ
.………………….
Standard enthalpy of 0
atomization (∆ H a ) 10
1HF(g) → H(g) + F(g) ∆H=+565 kJ
.………………….
Standard enthalpy of 0
atomization (∆ H a ) 11
1NaOH(s) → NaOH(aq) ∆H=-42.7 kJ
.………………….
Standard enthalpy of 0
solution (∆ H sol ) 12
1Na2NO3(s) → Na2NO3 (aq) ∆H=+20.5 kJ
.………………….
Standard enthalpy of 0
solution (∆ H sol ) 13
HCl(aq)+NaOH(aq)→ NaCl(aq) +1H2O(l) ∆H=-57.1 kJ
.………………….
Standard enthalpy of neutralization 0
(∆ H neut ) 14
HNO3(aq)+KOH(aq)→ KNO3(aq) +1H2O(l) ∆H=-57.3 kJ
.………………….
Standard enthalpy of neutralization 0
(∆ H neut )
2) Based on the data above answer the following questions No Questions 1 Based on the thermochemistry equation table above (no 1,2, and 3) a. How many moles of substances that melted, evaporated, and sublimated? b. What is standard enthalpy of fusion? c. What is standard enthalpy of vaporization? d. What is standard enthalpy of sublimation?
Answer a. ………………………………………… ……………………………………….. b. ……………………………………….. ……………………………………….. c. ……………………………………….. ……………………………………….. d. ……………………………………….. ………………………………………..
2
Based on the thermochemistry equation table above (no 4 and 5) a. How many moles of compound that form their elements? b. What is standard enthalpy of formation?
a. ………………………………………… ……………………………………….. b. ……………………………………….. ………………………………………..
3
Based on the thermochemistry equation table above (no 6, 7 and 8) a. How many moles of substance that combusted? b. What is the sign of enthalpy change of thermochemistry no. 6, 7 and 8?
a. ………………………………………… ……………………………………….. b. ……………………………………….. ………………………………………..
Thermochemistry/sman3malang/;by m. hariyanto
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c. What is standard enthalpy of combustion? 4
5
6
Based on the thermochemistry equation table above (no 9 and 10) a. How many moles of substance that atomized into their atoms? b. What is the sign of enthalpy change of thermo chemistry no 9 and 10? c. What is standard enthalpy of atomization? Based on the thermochemistry equation table above (no 11 and 12) a. How many moles of substance that dissolved into the solvent? b. What is standard enthalpy of solution?
Based on the thermochemistry equation table above (no 13 and 14) a. How many moles of water that produced at the process? b. What is the sign of enthalpy change of thermo chemistry no 13 and 14? c. What is standard enthalpy of neutralization?
Thermochemistry/sman3malang/;by m. hariyanto
c. ……………………………………….. ………………………………………..
a. ………………………………………… ……………………………………….. b. ……………………………………….. ……………………………………….. c. ……………………………………….. ………………………………………..
a. ………………………………………… ……………………………………….. b. ……………………………………….. ………………………………………..
a. ………………………………………… ……………………………………….. b. ……………………………………….. ……………………………………….. c. ……………………………………….. ………………………………………..
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3) Conclude the definition of each type of reaction/process by completing the following table! No 1
Type of Enthalpy Change
General Equation
Standard enthalpy of fusion (∆ H
2
Definition
0 fus
X(s) → X(l)
∆H=+x kJ
)
Standard enthalpy of 0
vaporization (∆ H vap )
3
Standard enthalpy of 0
sublimation (∆ H sub )
4
Standard enthalpy of
Element X + element Y → Compound XY ∆H=+/- x kJ
0 f
formation (∆ H )
5
Standard enthalpy of 0
combustion (∆ H c )
6
Standard enthalpy of 0
atomization (∆ H a )
7
Standard enthalpy of 0
solution (∆ H sol )
8
Standard enthalpy of neutralization 0
(∆ H neut )
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01.
What is the type of the following process? a. I2(s) → I2(g) b. MgC2(s) → MgC2(aq) c. C12H22O11(s) + 11O2(g) → 12CO2(g) + 11H2O(l) d. ½ N2(g) + 2H2(g) + ½ Cl2(g) → NH4Cl(s) e. 2HCl(aq) + Ca(OH)2(aq) → CaCl2(aq) + 2H2O(l)
02.
Write the thermochemistry equation of formation, if given the following data: a. ∆ H 0f C6H12O6(s) = -1260 kJ/mol b. ∆ H 0f Fe2O3(s) = -822 kJ/mol c. ∆ H 0f HBr(g) = -36.4 kJ/mol d. ∆ H 0f of nitrogen monoxide gas = +90.4 kJ/mol
03.
Write the thermochemistry equation of combustion, if given the following data: a. ∆ H c0 C6H12O6(s) = -2803 kJ/mol b. ∆ H c0 C(graphite) = -393.505 kJ/mol c. ∆ H c0 of Hydrogen gas = -286 kJ/mol d. ∆ H c0 B2H6(g) = -2035 kJ/mol
Thermochemistry/sman3malang/;by m. hariyanto
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04.
Write the thermochemistry equation of atomization, if given the following data: a. ∆ H a0 HCl(g) = +428.02 kJ/mol b. ∆ H a0 CH4 (g) = +1656 kJ/mol c. ∆ H a0 H2O(g) = +1856 kJ/mol d. ∆ H a0 NH3(g) = +1167 kJ/mol
05.
Write the thermochemistry equation of solution, if given the following data: 0 CaSO4(s) = -17.8 kJ/mol a. ∆ H sol 0 KNO3(s) = +34.9 kJ/mol b. ∆ H sol
06.
Write the thermochemistry equation of neutralization for aqueous solution Hydrochloric acid and aqueous solution of ammonia if given their standard of neutralization is -52.2 kJ/mole.
Thermochemistry/sman3malang/;by m. hariyanto
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07.
Given the standard enthalpy of solution of sodium hydroxide solid is -43 kJ/mol. Calculate the heat that released/absorbed for dissolving 800 grams of sodium hydroxide in the water.
Thermochemistry/sman3malang/;by m. hariyanto
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3rd worksheet MEASUREMENT OF ENTHALPY CHANGE FOR A REACTION BY EXPERIMENT
Drs. M. Hariyanto SMA Negeri 3 Malang (State Senior High School) Jl. Sultan Agung Utara No 7 Phone (0341) 324 768 Malang 65111 (website : http://psb-sman3malang.com )
There are five way to determine or calculate enthalpy change for a reaction, that is experiment/calorimetric, Hess’ Law, use data of standard enthalpy of formation (∆ H 0f ), use data of standard enthalpy of combustion (∆ H c0 ), and use data of standard enthalpy of atomization (∆ H a0 ) or Energy bonding (D). The following activity will determine enthalpy change for a reaction by experiment or calorimetry.
Before we determine or calculate the enthalpy change by calorimetric, all of you have to understand the relationship between heat (Q) and temperature change (∆T) 1. Information a. Calorimetry Calorimetry is measuring heat based on observing the temperature change when a body absorbs or releases energy as heat. The device used experimentally to determine the heat associated with chemical reaction is called calorimeter.
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Calorimeter 1) The relationship between heat (Q) and temperature change (∆T) Q = m.c. ∆T Q = C. ∆T
Q = heat (Joule) m = mass (g) c = specific heat capacity (J.K-1.g-1) C = heat capacity (J.K-1) ∆T = temperature change (K or ˚C)
2) Calculate heat of reaction by calorimetry Based on conservation energy law:
QABSORBED + QRELEASED = 0 If reaction/system releases heat, so surroundings (solution/water and calorimeter) absorb heat.
QCALORIMETER + QSOLUTION + QREACTION = 0 QREACTION = - (QCALORIMETER + QSOLUTION) NOTE: QCALORIMETER = CCALOIMETER. ∆T QSOLUTION = mSOLUTION.cSOLUTION. ∆T
Measurement of Enthalpy Change by Experiment Purposes Students are able to measure the enthalpy of reaction
Equipments and materials No 1 2 3 4 5 6 7
Equipments/materials Thermometer Graduated cylinder Polystyrene cup Glass container Glass stirring rod HCl solution NaOH solution
Capacity -10 to 100˚C 100 mL 1M 1M
Thermochemistry/sman3malang/;by m. hariyanto
Number 1 2 1 1 1 50 mL 50 mL
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Procedure (1) Place 50 mL of HCl solution into a polystyrene cup and measure its temperature. Place the cup a glass container (2) Measure 50 mL of 1M NaOH solution into a graduated cylinder and meausure its temperature (3) Mix the NaOH solution to HCl solution, stir briefly with a glass stirring rod, and note the maximum temperature reached.
Assignments (1) Record the data observation Initial Temperature HCl NaOH Average
Final Temperature
Temperature Change
(2) By assuming the head absorbed by the cup and the heat losses to the air are negligible, calculate the amount of energy released and calculate heat of reaction (QREACTION). The heat released is the heat of neutralization of 50 mL of 1M of HCl solution and 50 mL of 1M of NaOH solution.
(3) Calculate the enthalpy change per mole of water (H2O) that produced by reaction of 1 M of HCl solution and 1M of NaOH solution
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(4) Write the thermochemistry equation!
(5) What is the type of the enthalpy change?
01.
500 mL of 1M of nitric acid solution is mixed to 500 mL of 1M of potassium hydroxide solution. The temperature increases 7.5˚C, given the specific heat capacity of water is 4.20 J. ˚C-1.g-1. Calculate: a. calculate heat of reaction b. calculate the enthalpy of neutralization of nitric acid solution and potassium hydroxide solution c. write the thermal equation
02.
Given the enthalpy of combustion of carbon is -418 kJ/mol. How many grams of carbon to boil 500 mL of water at 25˚C; 1 atmospheric pressure. Given specific heat capacity of water is 4.18 J.K.g-1.
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4th worksheet HESS’ LAW Drs. M. Hariyanto SMA Negeri 3 Malang (State Senior High School) Jl. Sultan Agung Utara No 7 Phone (0341) 324 768 Malang 65111 (website : http://psb-sman3malang.com )
There are five way to determine or calculate enthalpy change for a reaction, that is experiment/calorimetric, Hess’ Law, use data of standard enthalpy of formation (∆ H 0f ), use data of standard enthalpy of combustion (∆ H c0 ), and use data of standard enthalpy of atomization (∆ H a0 ) or Energy bonding (D). The following activity will determine enthalpy change for a reaction by Hess’ Law.
Before we determine or calculate the enthalpy change by Hess’ Law, it is necessary to review the previous material, that is the characteristics of enthalpy change and diagram of energy level. 1. Answer the following questions! No Questions 1 Given thermochemistry equation:
Answer a. ………………………………………..
0
C(graphite) + O2(g) → CO2(g) ∆ H =-394 kJ
a. determine enthalpy change for formation of 2.2 g of carbon dioxide gas from graphite and oxygen gas b. determine enthalpy change for decomposition of 11 g of carbon dioxide gas into graphite and oxygen gas 2
Given thermochemistry equation:
b. ………………………………………..
a. …………………………………… 0
II. N2(g) + 2O2(g) → 2NO2(g) ∆ H =+68 kJ 0
III. O2(g) + 2NO(g) → 2NO2(g) ∆ H =-112 kJ
Draw the diagram of energy level of: a. reaction I
Thermochemistry/sman3malang/;by m. hariyanto
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b. reaction II
b. ……………………………………..
c. by combining the diagram of energy level of reaction I and reaction II, calculate ∆ H 0 of:
c. ……………………………………..
N2(g) + O2(g) → 2NO(g)
Hess’ Law Purposes Students are able to 1. understand Hess’ Law 2. use Hess’ Law to determine enthalpy change for q reaction
Information State function In thermodynamics, a state function, state quantity, or a function of state, is a property of a system that depends only on the current state of the system, not on the way in which the system acquired that state. A state function describes the equilibrium state of a system. For example, potential energy, internal energy, enthalpy and entropy are state quantities because they describe quantitatively an equilibrium state of thermodynamic systems.
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Assignment 1) Observe and complete the following table! No
1
Process
Diagram of Energy Level
Energy Cycle
Student is standing at the first floor. She are going to reach third floor through two route: Route I: Student reaches the third floor by stepping on the stairs through the second floor, and the third floor Route II: Student reaches the third floor directly by lift.
1stfloor →3rdfloor ∆Ep3
Route II: C(s) + O2(g) →CO2(g) ∆H3=-394kJ
Enthalpy (H)
Carbon dioxide gas is formatted from carbon and oxygen by two route: Route I: C(s) + ½ O2(g)→CO(g) ∆H1=-111kJ CO(g)+ ½ O2(g)→CO2(g) ∆H2=283kJ
Relationship among the energies
1stfloor →2ndfloor ∆Ep1 2ndfloor →3rdfloor ∆Ep2
The height of the second floor is 3 m and the height of third floor is 6 m from the first floor.
2
The Sum of Process/Reaction
Thermochemistry/sman3malang/;by m. hariyanto
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∆Ep3 = ∆Ep1 + ∆Ep2 +
2) Based on the data above, answer the following questions! No Questions 1 a. Compare the magnitude of potential energy change (process 1) for route I (one step)and route II ( two step), is it the same or different? b. Based on the answer of question 1a, does the magnitude of potential change depend on the pathway of process? c. Conclude the magnitude of potential energy of one step process and a series steps of process. 2
Answer
a. Compare the magnitude of enthalpy change (process 2) for route I (one step)and route II ( two step), is it the same or different? b. Based on the answer of question 2a, does the magnitude of enthalpy change depend on the pathway of process? c. Conclude the magnitude of enthalpy change of one step process and a series steps of process.
Conclusion The answer of assignment no 2c is the expression of Hess’ Law, conclude it! HESS’ LAW The magnitude of enthalpy change in going on from some initial state (a particular set of reactants) to some final state ( a particular of products) is dependent/independent*) of the pathway, the enthalpy change is the same/different*) whether the reaction take place in one step or in a series of steps.
Thermochemistry/sman3malang/;by m. hariyanto
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01. Given the thermal equation: N2(g) + O2(g) → 2NO(g) ∆H=180 kJ 2NO(g) + O2(g) → 2NO2(g) ∆H=-112 kJ Calculate the enthalpy change of reaction N2(g) + O2(g) → 2NO2(g) by the following methods: a. diagram of energy level b. energy cycles c. summing of reactions
02. Given the thermal equation: C(graphite) + O2(g) → CO2(g) ∆H=-394 kJ C(diamond) + O2(g) → CO2(g) ∆H=-396 kJ Calculate the enthalpy change of reaction C(graphite) → C(diamond) by the following methods: a. diagram of energy level b. energy cycles c. summing of reactions
Thermochemistry/sman3malang/;by m. hariyanto
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03. Given the following equation: ∆H=-822 kJ 2Fe(s) + 3/2 O2(g) → Fe2O3(s) ∆H=-110.5 kJ C(graphite) + O2(g) → CO2(g) Determine enthalpy change of the following reaction (by method of energy cycle and summing reactions): Fe2O3(s) + 3C(graphite) → 2Fe(s)+ CO2(g)
04. Given the following data: ∆H=-394 kJ (a) C(s) + O2(g) → CO2(g) (b) C3H4(g) + 4O2 (g) → 3CO2(g) + 2H2O(l) ∆H=-1938 kJ ∆H=-286 kJ (c) H2(g) + ½ O2(g) → H2O(l) Calculate ∆H for the synthesis of propyne (C3H4) from its elements, according to the equation by method of energy cycle and summing the reactions 3C(s) + 2H2(g) → C3H4(g)
Thermochemistry/sman3malang/;by m. hariyanto
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05. Given the following data: ∆H=-283 kJ (a) CO(g) + ½ O2(g) → CO2(g) ∆H=-286 kJ (b) H2(g) + ½ O2(g) → H2O(l) (c) CH3OH(l)+ 3/2 O2(g)→ CO2(g)+2H2O(l) ∆H=-715 kJ Calculate ∆H for the following reaction by method of summing the reactions CO(g) + 2H2(g) → CH3OH(l)
06. Given the following data: ∆H=-1273 kJ (a) 2B(s) + 3/2 O2(g) → B2O3(s) (b) B2H6(g) + 3O2 (g) → B2O3(s) + 3H2O(g) ∆H=-2035 kJ ∆H=-286 kJ (c) H2(g) + ½ O2(g) → H2O(l) ∆H=+44 kJ (d) H2O(l)→ H2O(g) Calculate ∆H for the synthesis of diborane (B2H6) from its elements, according to the equation by method of summing the reactions 2B(s) + 3H2(g) → B2H6(g)
07. Given the following data: ∆H=-102 kJ PH3(g) + HI(g) → PH4I(s) ∆H=+5.4kJ P(s) + 3/2 H2(g) → PH3(g) ∆H=+53kJ H2(g) + I2(g) → 2HI(g) Calculate the heat released/absorbed for formation of 8.1 g of PH4I (Mr=162).
Thermochemistry/sman3malang/;by m. hariyanto
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Additional Notes
Thermochemistry/sman3malang/;by m. hariyanto
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5th worksheet CALCULATION ENTHALPY CHANGE FOR A REACTION BASED ON: 9 THE DATA OF STANDARD ENTHALPY OF FORMATION 9 THE DATA OF STANDARD ENTHALPY OF COMBUSTION 9 THE DATA OF STANDARD ENTHALPY OF ATOMIZATION/BONDING ENERGY
Drs. M. Hariyanto SMA Negeri 3 Malang (State Senior High School) Jl. Sultan Agung Utara No 7 Phone (0341) 324 768 Malang 65111 (website : http://psb-sman3malang.com )
Enthalpy change for a reaction can be determined by experiment/calorimetric, Hess’ Law, based on the data of standard enthalpy of formation, based on the data of standard enthalpy of combustion, based on the data of bonding energy. The following activities are the three way to calculate enthalpy change for a reaction.
CALCULATION ∆HREACTION BASED ON THE DATA OF ∆Hf Purposes Students are able to calculate the enthalpy change for a reaction based on the data of standard enthalpy of formation
Assignments 1) Read and complete the following table based on the previous material of Hess’ energy cycle
Thermochemistry/sman3malang/;by m. hariyanto
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No
1
2
Process
The reactants react each other to produce the products accompanied by ∆Hreaction. Each reactant is formed from its elements accompanied by ∆Hf REACTANT and each product is formed from its elements by accompanied by ∆Hf PRODUCT 1. Draw the direction of arrow at energy cycle 2. write the relationship among ∆Hreaction, ∆Hf REACTANT, and ∆Hf PRODUCT Propyne gas (C3H4) is combusted to produce carbon dioxide gas (CO2) and water (H2O) accompanied by ∆Hreaction. C3H4(g), CO2(g), and H2O(l) are formed from their elements, C(s), H2(g), and O2(g) accompanied by ∆Hf C3H4(g), ∆Hf CO2(g), and ∆Hf H2O(l)
Thermochemistry/sman3malang/;by m. hariyanto
Hess’ Energy Cycle
∆Hreaction
Reactants
Products
Relationship among the enthalpy change
∆Hreaction=……………………………..
∆Hf PRODUCT
∆Hf REACTANT Elements
∆Hreaction
C3H4(g) + 4O2 (g) → 3CO2(g) + 2H2O(l) ∆Hf C3H4(g)
3.∆Hf CO2(g) 2.∆Hf H2O (l)
C(s) + 2H2(g) + 4O2(g)
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∆Hreaction=……………………………..
2) Conclude! What is the relationship among enthalpy change of reaction (∆Hreaction), the sum of standard enthalpy of formation of reactants (∑∆Hf of reactants), and the sum of standard enthalpy of formation of products (∑∆Hf of products)
Additional Notes
CALCULATION ∆HREACTION BASED ON THE DATA OF ∆HC Purposes Students are able to calculate the enthalpy change for a reaction based on the data of standard enthalpy of combustion
Assignments 1) Read and complete the following table based on the previous material of Hess’ energy cycle
Thermochemistry/sman3malang/;by m. hariyanto
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No
1
2
Process
The reactants react each other to produce the products accompanied by ∆Hreaction. Each reactant is combusted to produce the product of combustion accompanied by ∆Hc REACTANT and each product also is combusted to produce the products of combustion by accompanied by ∆Hc PRODUCT 1. Draw the direction of arrow at energy cycle 2. write the relationship among ∆Hreaction, ∆Hc REACTANT, and ∆Hc PRODUCT Propyne gas (C3H4) is formed from its elements, C(s) and H2(g) accompanied by ∆Hreaction. C(s), H2(g), and C3H4(g) are combusted to produce carbon dioxide gas (CO2) and water (H2O) accompanied by ∆Hc C(s), ∆Hc H2(g), and ∆Hc C3H4(g).
Hess’ Energy Cycle
∆Hreaction
Reactants
∆Hc
Products
∆Hreaction=……………………………..
∆Hc PRODUCT
REACTANT
Products of combustion
3C(s)
+ 2H2 (g)
∆Hreaction
→
3.∆Hc C(s) 2.∆Hc H2(g)
3CO2(g) + 2H2O(l)
Thermochemistry/sman3malang/;by m. hariyanto
Relationship among the enthalpy change
page 38
C3H4(g) ∆HcC3H4(g)
∆Hreaction=……………………………..
2) Conclude! What is the relationship among enthalpy change of reaction (∆Hreaction), the sum of standard enthalpy of combustion of reactants (∑∆Hc of reactants), and the sum of standard enthalpy of combustion of products (∑∆Hc of products)
Additional Notes
CALCULATION ∆HREACTION BASED ON THE DATA OF ∆Ha or Bonding Energy Purposes Students are able to calculate the enthalpy change for a reaction based on the data of bonding energy
Pre-knowledge Before to use data of bonding energy to calculate the enthalpy change for a reaction, we are going to review how to draw the structure formula or displayed formula, because it show the number and type of covalent bonding.
Thermochemistry/sman3malang/;by m. hariyanto
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Answer the following questions! No Questions 1 Draw the structure formula for the following substance and how many bonds of each type of bonding? a. H2 b. H2S c. NH3 d. C2H6 e. C2H4 f. C2H2
Answer
Information 1. Bonding energy of diatomic molecule Bonding energy is the amount of energy required to break one mole of bond in gaseous phase of covalent substance to form product in the gaseous phase at constant temperature and pressure. So bonding energy of diatomic molecule is the same with enthalpy of atomization. Example: Enthalpy atomization (∆Ha) of F2(g)= +159 kJ/mol, so the thermochemistry equation is: F2(g) → 2F(g) ∆H=+159 kJ or F-F(g) → 2F(g) ∆H=+159 kJ Bonding energy of F-F in F2 (DF-F)=+159 kJ For diatomic molecule: Bonding Energy (D) = Enthalpy of atomization (∆Ha) 2. Bonding energy of polyatomic molecule Bonding energy is the average of enthalpy of atomization for a number of different species (molecules or ions) containing particular bonding. Example: Enthalpy atomization (∆Ha) of H2O(g)= +926.7 kJ/mol, so the thermochemistry equation is: → 2H(g) + O(g) ∆H=+926.7 kJ Or H-O-H(g) → 2H(g) + O(g) ∆H=+926.7 kJ H2O(g) The number of O-H bond in per mole of H2O is two moles, so Bonding energy of O-H=
926.7kJ =463.4 kJ/mole 2 moles
For polyatomic molecules: Bonding Energy (D) =
Enthalpy of atomization number of mole of bond
Thermochemistry/sman3malang/;by m. hariyanto
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Assignments 1) Read and complete the following table based on the previous material of Hess’ energy cycle No
1
2
Process
The reactants react each other to produce the products accompanied by ∆Hreaction. Each reactant is atomized to produce their atoms accompanied by ∆Ha REACTANT or ∑DREACYANT and each product also is atomized to produce their by accompanied by ∆Ha PRODUCT or ∑DPRODUCT a. Draw the direction of arrow at energy cycle b. write the relationship among ∆Hreaction, D REACTANT, and DPRODUCT Propene gas (C3H4) is hydrogenised to produce Propyne gas (C3H4) accompanied by ∆Hreaction. C3H4(g), H2(g), and C3H4(g) are atomized to produce their atoms, C(g) and H(g) accompanied by ∆Ha C3H4(g), ∆Ha H2(g), and ∆Ha C3H4(g). ∆Ha C3H6=1.DC=C+1.DC-C+6.DC-H ∆Ha C3H4=1.DC≡C+1.DC-C+4.DC-H ∆Ha H2=1.DH-H
Thermochemistry/sman3malang/;by m. hariyanto
Hess’ Energy Cycle
∆Hreaction
Reactants
Products
Relationship among the enthalpy change
∆Hreaction=……………………………..
∑D PRODUCT
∑DREACTANT Atoms
C3H4(g)
∆Hreaction
+ H2 (g)
∆Ha C3H4
→
∆Ha H2
C3H6(g) ∆HaC3H6
3Cg)+ 6H(g)
page 41
∆Hreaction=……………………………..
2) Conclude! What is the relationship among enthalpy change of reaction (∆Hreaction), the sum of bonding energy of reactants (∑D of reactants), and the sum of bonding energy of products (∑D of products)
Additional Notes
01. Calculate enthalpy change of the following reaction: 3C(s) + F2O3(s) → 2Fe(s) + 3CO(g) Given: ∆Hf F2O3(s)= -822 kJ/mole ∆Hf CO(g) = -110 kJ/mole
Thermochemistry/sman3malang/;by m. hariyanto
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02. The lunar module which landed the first man on the Moon in 1969 used methylhydrazine, CH3NHNH2, and dinitrogen tetraoxide as propellants. The equation reaction in the engine is given as follows: 4CH3NHNH2(l) + 5N2O4(l) → 4CO2(g) + 9N2(g) + 12H2O(l) Calculate enthalpy change of reaction if the appropriate enthalpy changes of formation are given below: CH3NHNH2(l) = +53kJ/mole =-20kJ/mole N2O4(l) =-394kJ/mole CO2(g) =-285kJ/mole H2O(l)
03. Given standard enthalpy of combustion for some substances: ∆Hc C(s) = -394kJ/mole ∆Hc H2(g) = -286kJ/mole ∆Hc C3H4(g)= -1938kJ/mole Calculate standard enthalpy of formation for propyne (C3H4)
04. Changing 2 mole of C(graphite) to C(diamond) need 2 kJ of heat. Calculate standard enthalpy of combustion of C(diamond) if given standard enthalpy of combustion of C(graphite) is 396kJ/mole.
Thermochemistry/sman3malang/;by m. hariyanto
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05. Calculate the heat released by combustion of 5.6 g ethylene, C2H4 gas if he appropriate of bonding energies are given below: DC=C = + 611kJ/mole DO=O = +498kJ/mole DC=O = +736kJ/mole DH-O = +464kJ/mole
06. Given the following data: = + 946kJ/mole DN≡N = +436kJ/mole DH-H ∆Hf NH3(g)= -46kJ/mole Calculate the bonding energy of N-H in ammonia gas.
Thermochemistry/sman3malang/;by m. hariyanto
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