Mole And Grams Lab 632r4n

Chemistry

Name: Megen Cunningham Period _1__ Date: Dec/5/2013

Moles, Molecules, and Grams Lab The Mole Concept Unit 4 As we’ve already discussed in class, it’s easy to make conversions between moles, molecules/formula units, and grams. For example, if we want to go from moles to grams, we use the molar mass to make this conversion. If we want to go from moles to molecules, we use Avogadro’s number, or 6.02 x 1023. Finally, if we want to go from grams to molecules/formula units, we just use a two step process where we first convert from grams to moles, and then from moles to molecules/F.U. Visually, it looks like this: Molar mass Grams

6.02 x 1023 Moles

Molecules/Formula Units

In this lab, we will be weighing out five different substances then finding out how many moles and molecules/F.U. of each one we have. Prelab: If you measure out 25.0 grams of NaOH in this lab, how many moles of NaOH would you have? How many formula units? 1 mole 25.0g NaOH *---------------------- = 0.63 moles NaOH 39.997g NaOH 6.02 * 10^23 molecules 0.63 moles NaOH *---------------------------------=3.76 * 10^23 molecules of NaOH 1 mole Lab: In this lab, there are five different balances set up, each of which has a labeled substance in a little jar next to it. Your job is to find out how many moles and how many molecules of each substance are in the canister. Some information you might find useful: • sand • baking soda (NaHCO3) • chalk (CaCO3) • table salt (NaCl) • sugar: sucrose (C12H22O11)

Make sure that your lab has a data table that contains the following: • The name of each of these substances • The formula for each of these substances • The molar mass of each of these substances • The mass in grams of each of these substances. When you are done weighing each material, calculate the number of moles of each material, and the number of molecules of each one, and put them in the right space. All calculations must be shown on lined paper with all conversion factors and unit cancelling. Data Table: Plate Weight: 2.51g Name

Sand

Chalk

Table salt

Sugar

SiO2 60.09g

Baking Soda NaHCO3 84.01g

Formula Molar Mass Mass in Grams

CaCO3 100.1g

NaCl 58.44g

C12H22O11 342.3g

1.05

1.37

1.75

0.85

0.70

Calculations: Using your data, find the following values. Make sure to show all work and write all numbers with the correct significant figures. 1a. Number of moles of sand: 0.017 moles SiO2 1 mole 1.05 g SiO2 * ------------------------------------- = 0.017 moles SiO2 60.09g SiO2 b. Number of molecules of sand: 1.05 * 10^22 molecules SiO2 6.02 * 10^23 0.017 moles SiO2 *----------------------= 1.05 * 10^22 molecules SiO2 1 mole

2a. Number of moles of baking soda: 0.016 moles NaHCO3

1 mole 1.37g NaHCO3 *--------------------------= 0.016 moles NaHCO3 84.01g NaHCO3 b. Number of formula units of baking soda: 9.82 * 10^21 molecules NaHCO3 6.02 * 10^23 0.016 moles NaHCO3 *----------------------= 9.82 * 10^21 molecules NaHCO3 1 mole 3. Number of formula units of chalk: 1.05*10^22 molecules CaCO3 Hint: String two conversions together 1 mole

1.75g CaCO3 *

6.02 * 10^23 = 0.017 moles CaCO *--------------------= 1.05*10^22 molecules CaCO3 ------------------------------------3 100.1g CaCO3 1 mole

4. Number of formula units of salt: 8.76*10^21 molecules NaCl

1 mole 0.85g NaCl *

-------------------------------------=

58.44g NaCl

6.02 * 10^23 0.015 moles NaCl*--------------------= 8.76*10^21 molecules NaCl 1 mole

5. Number of molecules of sugar: 1.23 * 10^21 molecules C12H22O11

1 mole 0.70g C12H22O11 *

-------------------------------------=

342.3g

12H22O11

6.02 * 10^23 0.002 moles C12H22O11 --------------------= 1.23 * 10^21 molecules C12H22O11 1 mole

Post Lab Questions: 1. Which of the materials we worked with had the largest number of molecules/formula units? Was this the material that had the largest weight? Why? Baking Soda with had the largest number of molecules/formula units and the largest molar mass weight of 84.01g. Baking soda has the most elements in it.

2. Water has a molecular formula of H2O. If I have 50.0 g of water, how many moles of water do I have? How many molecules? Molar Mass= 18.015 g/mol 1 mole 6.02 * 10^23 50.0 g H2O*----------------------=2.78 mole H2O*------------------=1.67 molecules H2O 18.015 g H2O 1 mole

3. Butane has a molecular formula of C4H10. If I have 50.0 grams of butane, how many moles of natural gas do I have? How many molecules? Molar Mass= 58.12 g/mol 1 mole 6.02 * 10^23 50.0g C4H10*-----------------=0.86 mole C4H10*--------------------=5.18*10^23 molecules C4H10 58.12g C4H10 1 mole

4. I had the same weight of water and butane in problems 3 and 4. Why didn’t the answer come out the same? Explain. Because they have different molar masses, H2O has a molar mass of 18.015 g/mol, and C4H10 had molar mass of 58.12 g/mol, that’s why they have different amounts of molecules.

Chalk

Sugar

Pictures Baking Soda

Sand

Salt