Quiz 2 o532j
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Quiz 2 Due: 11:59pm on Wednesday, September 19, 2012 Note: You will receive no credit for late submissions. To learn more, read your instructor's Grading Policy
Question 1 Give the name or chemical formula, as appropriate, for each of the following acids.
Part A , ANSWER: bromic acid
Correct
Part B , ANSWER: hydrobromic acid
Correct
Part C , ANSWER: phosphoric acid
Correct
Part D hypochlorous acid, Express your answer as a chemical formula. ANSWER:
Correct
Part E iodic acid,
Express your answer as a chemical formula. ANSWER:
Correct
Part F sulfurous acid. Express your answer as a chemical formula. ANSWER:
Correct
Question 2 Learning Goal: To learn to write the systematic name of ionic compounds given the chemical formula and to write the chemical formula given the systematic name. Ionic bonds form when one atom completely transfers one or more electrons to another atom, resulting in the formation of ions. Positively charged ions (cations) are strongly attracted to negatively charged ions (anions) by electrical forces. All chemical compounds can be named systematically by following a series of rules. Binary ionic compounds are named by identifying first the positive ion and then the negative ion. Naming compounds with polyatomic ions involves memorizing the names and formulas of the most common ones.
Part A Give the systematic name for the compound
.
Hint 1. How to approach the problem When naming ionic compounds, the cation is identified first and the anion is identified second.
Hint 2. Name the anion What is the name of the polyatomic anion
?
Hint 1. Naming polyatomic ions It is generally necessary to memorize the names of polyatomic ions such as
(hydroxide),
(ammonium), or
(sulfite).
However, there are a few guidelines: The names of most polyatomic ions end in ite or ate. Oxoanions are ions in which a given element combines with different numbers of oxygen atoms. For example, sulfur can combine with three or four oxygen atoms, forming or . When there are only two oxoanions, the ion with fewer oxygen atoms has the ending ite, and the ion with more oxygen atoms has the ending ate. The first part of the name is taken from the name of the element that combines with the oxygen atoms. Thus, is the sulfite ion and is the sulfate ion. Nitrogen forms two oxoanions,
and
.
ANSWER: nitrate
ANSWER: aluminium nitrate
Correct Aluminum is a metal that has only one oxidation state. Therefore it is not necessary to write III in parentheses in the systematic name. Only those metals with more than one oxidation state must have its state written in the name.
Part B Give the systematic name for the compound
.
Hint 1. How to approach the problem When naming ionic compounds, the cation is identified first and the anion is identified second. If the metal has more than one oxidation state, identify the oxidation state using a Roman numeral in parentheses immediately after the metal name.
Hint 2. Name the anion What is the systematic name of the anion
?
Hint 1. Naming polyatomic ions It is generally necessary to memorize the names of polyatomic ions such as
(hydroxide),
(ammonium), or
(sulfite).
However, there are a few guidelines: The names of most polyatomic ions end in ite or ate. Oxoanions are ions in which a given element combines with different numbers of oxygen atoms. For example, nitrogen can combine with two or three oxygen atoms, forming or . When there are only two oxoanions, the ion with fewer oxygen atoms has the ending ite, and the ion with more oxygen atoms has the ending ate. The first part of the name is taken from the name of the element that combines with the oxygen atoms. Thus, is the nitrite ion and is the nitrate ion. Sulfur forms two oxoanions,
and
.
ANSWER: sulfate
Hint 3. Determine the oxidation number What is the charge of the iron cation in this ionic compound. ANSWER:
3 2 0 +1 +2 +3
ANSWER: iron(III) sulfate
Correct Although it seems like a small difference, iron(II) and iron(III) behave much differently chemically. They even form different-colored compounds because of the number of electrons they have to bond. Therefore it is very important to specify which oxidation state is being used.
Part C Write the formula for the compound magnesium oxide. Express your answer as a chemical formula.
Hint 1. How to approach the problem Use the periodic table to determine the charge for each ion. Because this is a neutral ionic compound, the positive charges must equal the negative charges. Reduce the subscript on each ion to its lowest whole number ratio.
Hint 2. Determine the charge of the anion What is the charge of the oxide ion?
Hint 1. Group 16 elements Oxygen is in group 16 on the periodic table. This group is also known as group 6A using the U.S. system. Main group nonmetals usually form anions whose charge is equal to the U.S. system group number minus eight.
ANSWER: 4 3 2 1 0 +1 +2 +3
Hint 3. Determine the charge of the cation What is the charge of the magnesium ion?
Hint 1. Alkaline earth metals By consulting the periodic table, we can determine that magnesium is an alkaline earth metal. Main group metals usually form cations whose charge is equal to the group number.
ANSWER: 2 1 0 +1 +2 +3 +4
ANSWER:
Correct All of the elements in group 2 form ions with a +2 charge. That is because all of these elements need to lose two electrons to gain stability. After losing the electrons, there is an excess of two protons, which results in a +2 charge.
Part D Write the formula for the compound lead(II) phosphate. Express your answer as a chemical formula.
Hint 1. How to approach the problem The oxidation number of the cation is given. The anion is polyatomic, so you will have to look up its formula and charge. Because this is a neutral ionic compound, the positive charges must equal the negative charges. Reduce the subscript on each ion to its lowest whole number ratio.
Hint 2. Determine the formula for the phosphate ion What is the formula for the phosphate anion?
Hint 1. How to approach the problem The phosphate ion is an oxoanion composed of two elements: phosphorus and oxygen. Consider that a similar ion, the phosphite ion, has the formula .
ANSWER:
Hint 3. Balance the charges Lead(II) has a charge of +2 and phosphate has a charge of
3. Therefore, the lead(II) phosphate formula must have _____ lead(II) ions and
_____ phosphate ions for the charges to balance.
Hint 1. Charges in neutral compounds Because this is a neutral ionic compound, the total number of positive charges [from the lead(II) ion] must equal the total number of negative charges (from the phosphate ion). The lead(II) ion has a +2 charge and the phosphate ion has a 3 charge. Therefore, if there were only one lead(II) ion and one phosphate ion, the overall charge would be
1, because
. To have an overall charge of 0, this compound will have
more than one of each ion. That is, both ions—iron(II) and chloride—will have subscripts.
ANSWER: one / one one / two one / three two / one two / three three / two
ANSWER:
Correct Lead, like iron, has more than one oxidation state, so it is necessary to put the oxidation state of the metal in brackets. Elements in group 1 and 2 only have one oxidation state and so there is no need for Roman numerals in their systematic name.
Question 3 The coefficients in a balanced chemical equation provide the mole-to-mole stoichiometry among the reactants and products. The molar mass (in can be used as the conversion factor between moles and the mass of a substance. Thus, the balanced equation and molar masses can be used in conjunction with one another to calculate the masses involved in a reaction.
Complete combustion of methane When methane (
) burns, it reacts with oxygen gas to produce carbon dioxide and water. The unbalanced equation for this reaction is
This type of reaction is referred to as a complete combustion reaction.
Part A
)
What coefficients are needed to balance the equation for the complete combustion of methane? Enter the coefficients in the order
,
,
, and
, respectively. Express your answer as four integers, separated by commas (e.g., 1,2,3,4).
Hint 1. How to approach the problem First, balance the carbon atoms. Second, balance the hydrogen atoms. Third, balance the oxygen atoms. Finally, double check that all atoms are balanced.
ANSWER: 1,2,1,2
Correct The balanced chemical equation is therefore:
Part B What mass of carbon dioxide is produced from the complete combustion of 4.70!10"3 of methane? Express your answer numerically in grams.
Hint 1. How to approach the problem First, convert the mass of methane to moles. Then, use the balanced equation to convert moles of methane to moles of carbon dioxide. Finally, convert moles of carbon dioxide to grams.
Hint 2. Determine the number of moles of methane How many moles of methane are in 4.70!10"3 ? Express your answer numerically in moles.
Hint 1. Determine the molar mass of methane What is the molar mass of methane,
? Use the periodic table as needed.
Express your answer numerically in grams per mole. ANSWER: 16.0
ANSWER: 2.93!10"4
Hint 3. Find the number of moles of carbon dioxide How many moles of
are produced from the given amount of
Express your answer numerically in moles.
?
Hint 1. Determine the stoichiometry between methane and carbon dioxide Which of the following would be the correct stoichiometric ratio to convert from moles of methane to moles of carbon dioxide? ANSWER:
ANSWER: 2.93!10"4
Hint 4. Determine the molar mass of carbon dioxide What is the molar mass of carbon dioxide? Use the periodic table as needed. Express your numerically in grams per mole. ANSWER: 44.0
ANSWER: 1.29!10"2
Correct
Part C What mass of water is produced from the complete combustion of 4.70!10"3 of methane? Express your answer numerically in grams.
Hint 1. How to approach the problem First, convert the mass of methane to moles. Second, use the balanced equation to convert moles of methane to moles of water. Finally, convert moles of water to grams of water.
Hint 2. Find the number of moles of water How many moles of
are produced from the given amount of
?
Express your answer numerically in moles.
Hint 1. How to approach the problem First, determine the number of moles of methane that react (you should have already figured this out in Part B). Second, determine the
mole ratio of water to methane given in the balanced equation (which you figured out in Part A). Finally, use the mole ratio to convert from moles of methane to moles of water.
Hint 2. Determine the stoichiometry between methane and water Which of the following would be the correct stoichiometric ratio to convert from moles of methane to moles of water? ANSWER:
Correct Use the conversion formula
to convert the given number of moles of methane to the corresponding number of moles of water.
ANSWER: 5.86!10"4
Answer Requested
Hint 3. Determine the molar mass of water What is the molar mass of water? Use the periodic table as needed. Express your answer numerically in grams per mole. ANSWER: 18.0
Answer Requested The molar mass in the form
can be used to convert moles to grams.
ANSWER: 1.06!10"2
Answer Requested
Part D What mass of oxygen is needed for the complete combustion of 4.70!10"3 of methane? Express your answer numerically in grams.
Hint 1. How to approach the problem First, convert the mass of methane to moles. Second, use the balanced equation to convert moles of methane to moles of oxygen. Finally, convert moles of oxygen to grams of oxygen.
Hint 2. Convert to moles of oxygen How many moles of
are needed to react with the given amount of
?
Express your answer numerically in moles.
Hint 1. How to approach the problem First, determine the number of moles of methane that react (you should have already figured this out in Part B). Second, determine the mole ratio of oxygen to methane given in the balanced equation (which you figured out in Part A). Finally, use the mole ratio to convert from moles of methane to moles of oxygen.
Hint 2. Determine the stoichiometry between methane and oxygen Which of the following would be the correct stoichiometric ratio to convert from moles of methane to moles of oxygen? ANSWER:
ANSWER: 5.86!10"4
Hint 3. Determine the molar mass of oxygen What is the molar mass of
? Use the periodic table as needed.
Express your answer in grams per mole. ANSWER: 32.0
ANSWER: 1.88!10"2
Correct
Question 4 A phase diagram is a convenient means of representing the temperature and pressure dependence of a pure substance in a closed system. The typical phase diagram indicates which phase (solid, liquid, or gas) is stable at a given temperature and pressure. Boundaries separate these phase regions. When a boundary line is crossed owing to changes in temperature and/or pressure a phase change occurs.
Part A Identify each of the labeled points (indicated with letters) or changes (indicated with two letters separated by an arrow) shown on the phase diagram.
Match the words in the left-hand column with the appropriate blank in the sentences in the right-hand column.
Hint 1. Identify the regions of the phase diagram Identify which physical state is shown by each of the colored regions labeled with the letters X, Y, and Z on the phase diagram.
Drag each item to the appropriate bin.
Hint 1. Relation of pressure and temperature to phase High pressure and low temperatures tend to favor the condensed phases whereas low pressure and high temperatures tend to favor the gas state. Use the axes on the diagrams to help identify these conditions.
ANSWER:
Hint 2. Define the specific characteristics of the phase diagram Complete the following sentences related to phase diagrams. Match the words in the left-hand column with the appropriate blank in the sentences in the right-hand column. ANSWER:
ANSWER:
Correct
Part B The phase diagram for an organic compound is shown.
What is the normal boiling point of this compound? Express your answer numerically in degrees Celsius.
Hint 1. Definition of normal boiling point The normal boiling of a substance is the temperature required to establish liquid-vapor equilibrium at standard pressure. On a phase diagram, this point occurs where the liquid-vapor line crosses standard pressure.
Hint 2. Identify the value of standard pressure What is the value of standard pressure? Express your answer numerically in atmospheres. ANSWER: standard pressure = 1.00
ANSWER: normal boiling point = 150
Correct
Question 5 The fluorocarbon compound
has a normal boiling point of 47.6
, respectively. The heat of vaporization for the compound is 27.49
. The specific heats of
and
are 0.91
and 0.67
.
Part A Calculate the heat required to convert 73.5 of
from a liquid at 14.60
to a gas at 76.40
.
Express your answer using one decimal place. ANSWER: = 14.4
Correct
Question 6 Chemists often use molarity
, in
, to measure the concentration of solutions. Molarity is a common unit of concentration because the volume
of a liquid is very easy to measure. However, the drawback of using molarity is that volume is a temperature-dependent quantity. As temperature changes, density changes, which affects volume. Volume markings for most laboratory glassware are calibrated for room temperature, about 20 . Fortunately, there are several other ways of expressing concentration that do not involve volume and are therefore temperature independent. A mass of 0.630
of
is dissolved in 525
of water.
Part A Calculate the molality of the salt solution.
Hint 1. Formula for molality By definition
Hint 2. Solute vs. solvent In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, the solvent is the substance present in the greatest amount.
Hint 3. Determine the number of kilograms of water Convert the mass of water to kilograms. ANSWER:
0.525
ANSWER: 2.05!10"2
Correct
Part B Calculate the mole fraction of salt in this solution.
Hint 1. Formula for mole fraction By definition
Hint 2. Solute vs. solvent In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, the solvent is the substance present in the greatest amount.
Hint 3. Calculate the number of moles of NaCl How many moles of NaCl are in 0.630 ?
Hint 1. Find the molar mass of NaCl What is the molar mass of
?
Express your answer in grams per mole. ANSWER: 58.5
ANSWER: 1.08!10"2
Hint 4. Calculate the number of moles of water How many moles of water are in 525 ?
Hint 1. Find the molecular weight of water What is the molecular weight of water? Express your answer in grams per mole.
Hint 1. Formula for water
The chemical formula for water is
.
ANSWER: 18.0
ANSWER: 29.2
ANSWER: = 3.70!10"4
Correct
Part C Calculate the concentration of the salt solution in percent by mass.
Hint 1. Formula for percent by mass By definition
Hint 2. Solute vs. solvent vs. solution In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, the solvent is the substance present in the greatest amount. The word "solution" refers to solvent plus solute.
Hint 3. Find the mass of the solution What is the mass of this solution? Express your answer five significant figures. ANSWER: 525.63
ANSWER: 0.120 %
g
Correct The total mass of the solution in this case is 525.63 , which makes the percent by mass come to 0.11985617%. However, when rounded to the correct number of significant figures, the answer becomes 0.120%. Quite often, the mass of the solute is so small compared to the mass of the solution that
Part D Calculate the concentration of the salt solution in parts per million
Hint 1. Formula for ppm By definition
Hint 2. Solute vs. solvent vs. solution In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, the solvent is the substance present in the greatest amount. The word "solution" refers to solvent plus solute.
ANSWER: 1200
Correct The word percent means "per 100" (think of century). Therefore, an alternate name for percent by mass could be "parts per hundred." This should help you see the similarity between percent and parts per million:
Question 7 Indicate the type of solute-solvent interaction that should be most important in each of the following solutions.
Part A in benzene ANSWER: dispersion forces dipole-dipole forces ion-dipole forces hydrogen bonding
Correct
Part B methanol
in water
ANSWER: dispersion forces dipole-dipole forces ion-dipole forces hydrogen bonding
Correct
Part C in water ANSWER: dispersion forces dipole-dipole forces ion-dipole forces hydrogen bonding
Correct
Part D in acetonitrile ANSWER: dispersion forces dipole-dipole forces ion-dipole forces hydrogen bonding
Correct
Question 8
By referring to the figure , determine whether the addition of 40.0 solids to 100 of water at 40 will lead to a saturated solution.
Part A
ANSWER: saturated solution unsaturated solution
Correct
Part B
ANSWER: saturated solution unsaturated solution
Correct
Part C
ANSWER: saturated solution unsaturated solution
Correct
Part D
of each of the following ionic
ANSWER: saturated solution unsaturated solution
Correct
Question 9 Ascorbic acid (vitamin C, at 55
) is a water-soluble vitamin. A solution containing 80.5 of ascorbic acid dissolved in 230 of water has a density of 1.22
.
Part A Calculate the mass percentage. ANSWER: 25.9 %
Correct
Part B Calculate the mole fraction. ANSWER: 3.46!10"2
Correct
Part C Calculate the molality. ANSWER: 1.99
Correct
Part D Calculate the molarity of ascorbic acid in this solution. ANSWER: = 1.80
Correct
Question 10 Calculate the number of moles of solute present in each of the following solutions.
Part A 270
of 1.50
ANSWER: = 0.405
Correct
Part B 55.0
of an aqueous solution that is 1.50
ANSWER: = 7.59!10"5
All attempts used; correct answer displayed
Part C 80.0 of an aqueous solution that is 1.70% sucrose (
) by mass
ANSWER: = 3.97!10"3
Correct
Question 11 Part A Calculate the vapor pressure of water above a solution prepared by dissolving 38.0 of glycerin ( pressure of water at 343 ANSWER: = 222
is 233.7
.)
) in 135 of water at 343
. (The vapor
Correct
Part B Calculate the mass of ethylene glycol (
) that must be added to 1.00
. The vapor pressure of pure ethanol at 35
is
of ethanol (
) to reduce its vapor pressure by 12.0
at 35
torr.
ANSWER: = 184
Correct
Question 12 The molar mass of a compound expresses the ratio of mass to moles:
This quantity can be determined experimentally by accurately measuring the mass of the sample and determining the corresponding number of moles based on some property of the sample. Freezing point depression and osmotic pressure measurements are frequently used for this type of determination. In each instance, the number of moles is determined from the colligative property of the solution. For osmotic pressure measurements, the number of moles is calculated from the volume of the solution and the molarity. In freezing point depression measurements, the number of moles is derived from the molality of the solution.
Part A tert-Butyl alcohol is a solvent with a 11.6
of 9.10
of tert-butyl alcohol, the solution froze at 15.3
and a freezing point of 25.5
. When 0.807
of an unknown colorless liquid was dissolved in
.
Which of the following is most likely the identity of this unknown liquid?
Hint 1. How to approach the problem First, calculate the freezing point depression by subtracting the two freezing points: Next, calculate the molality,
, using the equation
Next, convert the mass of solvent to kilograms and use the definition of molality,
to determine the number of moles of solute, Finally, use the mass and number of moles of solute to calculate the molar mass in grams per mole.
Hint 2. Calculate the freezing point depression of the solution What is the value of the freezing point depression,
, of the solution?
Express your answer numerically in degrees Celsius. ANSWER: 10.2
Hint 3. Determine the molality of the solution
What is the molality of the solution? Express the concentration numerically as molality.
Hint 1. What equation to use Based on freezing point depression and the freezing point depression constant of the solvent, the following equation can be solved for molality:
ANSWER: 1.12
Hint 4. Convert the mass of solvent to kilograms What is the mass of the solvent in kilograms? Express the mass numerically in kilograms.
Hint 1. Conversion factor .
ANSWER: 1.16!10"2
Hint 5. Calculate the number of moles of solute present Using the molality and the kilogram mass of the solvent, calculate the number of moles of solute present in the solution. Express your answer numerically in moles. ANSWER: 1.30!10"2
Hint 6. Determine the molar mass of the solute What is the molar mass of the solute used in this experiment? Express your answer numerically in grams per mole.
Hint 1. What equation to use The applicable equation to calculate molar mass is
ANSWER: 62.1
ANSWER:
ethylene glycol (molar mass = 62.07
)
1-octanol (molar mass = 130.22 glycerol (molar mass = 92.09
) )
2-pentanone (molar mass = 86.13
)
1-butanol (molar mass = 74.12
)
Correct
Part B A protein subunit from an enzyme is part of a research study and needs to be characterized. A total of 0.135 of this subunit was dissolved in enough water to produce 2.00 of solution. At 28 the osmotic pressure produced by the solution was 0.138 . What is the molar mass of the protein? Express the molar mass numerically in grams per mole.
Hint 1. How to approach the problem To calculate the molar mass, a mass and the corresponding number of moles must be known. The mass is given in the problem and the number of moles can be calculated from the osmotic pressure. First, convert the temperature to kelvins and solve for molarity using the equation
where
. Next, convert the volume of solution to liters and use the definition of molarity,
to find the moles of solute. Finally, use the mass and number of moles of solute to calculate the molar mass.
Hint 2. Calculate the temperature in kelvins What is the temperature when converted to the Kelvin scale? Express the temperature in kelvins ANSWER: 301
Hint 3. Calculate the molarity of the solution Based on the osmotic pressure, what is the molarity of the protein solution? Express the concentration numerically in molar.
Hint 1. What equation to use Solve the following equation for the molarity:
ANSWER: 5.59!10"3
Hint 4. Convert the volume of the solution to liters
What is the volume of the protein solution in liters? Express the volume numerically in liters.
Hint 1. Conversion factor .
ANSWER: 2.00!10"3
Hint 5. Determine the number of moles of solute in the solution How many moles of solute are present in the protein solution? Express your answer numerically in moles.
Hint 1. What equation to use Solve the following equation for moles of solute:
ANSWER: 1.12!10"5
ANSWER: 1.21!104
Correct
Question 13 Part A List the following aqueous solutions in order of decreasing boiling point. 0.120 Rank items in order of decreasing boiling point. ANSWER:
glucose, 0.050
, 0.050
.
Correct
Question 14 Part A List the following aqueous solutions in order of decreasing freezing point: 0.040
glycerin (
), 0.020
, 0.030
Rank solutions from highest freezing point to lowest freezing point. To rank items as equivalent, overlap them. ANSWER:
phenol (
).
Correct
Question 15 Carbon disulfide
boils at 46.30
and has a density of 1.261
.
Part A When 0.250
of a nondissociating solute is dissolved in 400.0
constant for
?
of
, the solution boils at 47.46
. What is the molal boiling-point-elevation
ANSWER: = 2.34
Correct
Part B When 5.41 of a nondissociating unknown is dissolved in 50.0 unknown? Express your answer using two significant figures. ANSWER: = 260
Correct
Score Summary: Your score on this assignment is 90.9%. You received 13.64 out of a possible total of 15 points.
of
, the solution boils at 47.08
. What is the molecular weight of the
Question 1 Give the name or chemical formula, as appropriate, for each of the following acids.
Part A , ANSWER: bromic acid
Correct
Part B , ANSWER: hydrobromic acid
Correct
Part C , ANSWER: phosphoric acid
Correct
Part D hypochlorous acid, Express your answer as a chemical formula. ANSWER:
Correct
Part E iodic acid,
Express your answer as a chemical formula. ANSWER:
Correct
Part F sulfurous acid. Express your answer as a chemical formula. ANSWER:
Correct
Question 2 Learning Goal: To learn to write the systematic name of ionic compounds given the chemical formula and to write the chemical formula given the systematic name. Ionic bonds form when one atom completely transfers one or more electrons to another atom, resulting in the formation of ions. Positively charged ions (cations) are strongly attracted to negatively charged ions (anions) by electrical forces. All chemical compounds can be named systematically by following a series of rules. Binary ionic compounds are named by identifying first the positive ion and then the negative ion. Naming compounds with polyatomic ions involves memorizing the names and formulas of the most common ones.
Part A Give the systematic name for the compound
.
Hint 1. How to approach the problem When naming ionic compounds, the cation is identified first and the anion is identified second.
Hint 2. Name the anion What is the name of the polyatomic anion
?
Hint 1. Naming polyatomic ions It is generally necessary to memorize the names of polyatomic ions such as
(hydroxide),
(ammonium), or
(sulfite).
However, there are a few guidelines: The names of most polyatomic ions end in ite or ate. Oxoanions are ions in which a given element combines with different numbers of oxygen atoms. For example, sulfur can combine with three or four oxygen atoms, forming or . When there are only two oxoanions, the ion with fewer oxygen atoms has the ending ite, and the ion with more oxygen atoms has the ending ate. The first part of the name is taken from the name of the element that combines with the oxygen atoms. Thus, is the sulfite ion and is the sulfate ion. Nitrogen forms two oxoanions,
and
.
ANSWER: nitrate
ANSWER: aluminium nitrate
Correct Aluminum is a metal that has only one oxidation state. Therefore it is not necessary to write III in parentheses in the systematic name. Only those metals with more than one oxidation state must have its state written in the name.
Part B Give the systematic name for the compound
.
Hint 1. How to approach the problem When naming ionic compounds, the cation is identified first and the anion is identified second. If the metal has more than one oxidation state, identify the oxidation state using a Roman numeral in parentheses immediately after the metal name.
Hint 2. Name the anion What is the systematic name of the anion
?
Hint 1. Naming polyatomic ions It is generally necessary to memorize the names of polyatomic ions such as
(hydroxide),
(ammonium), or
(sulfite).
However, there are a few guidelines: The names of most polyatomic ions end in ite or ate. Oxoanions are ions in which a given element combines with different numbers of oxygen atoms. For example, nitrogen can combine with two or three oxygen atoms, forming or . When there are only two oxoanions, the ion with fewer oxygen atoms has the ending ite, and the ion with more oxygen atoms has the ending ate. The first part of the name is taken from the name of the element that combines with the oxygen atoms. Thus, is the nitrite ion and is the nitrate ion. Sulfur forms two oxoanions,
and
.
ANSWER: sulfate
Hint 3. Determine the oxidation number What is the charge of the iron cation in this ionic compound. ANSWER:
3 2 0 +1 +2 +3
ANSWER: iron(III) sulfate
Correct Although it seems like a small difference, iron(II) and iron(III) behave much differently chemically. They even form different-colored compounds because of the number of electrons they have to bond. Therefore it is very important to specify which oxidation state is being used.
Part C Write the formula for the compound magnesium oxide. Express your answer as a chemical formula.
Hint 1. How to approach the problem Use the periodic table to determine the charge for each ion. Because this is a neutral ionic compound, the positive charges must equal the negative charges. Reduce the subscript on each ion to its lowest whole number ratio.
Hint 2. Determine the charge of the anion What is the charge of the oxide ion?
Hint 1. Group 16 elements Oxygen is in group 16 on the periodic table. This group is also known as group 6A using the U.S. system. Main group nonmetals usually form anions whose charge is equal to the U.S. system group number minus eight.
ANSWER: 4 3 2 1 0 +1 +2 +3
Hint 3. Determine the charge of the cation What is the charge of the magnesium ion?
Hint 1. Alkaline earth metals By consulting the periodic table, we can determine that magnesium is an alkaline earth metal. Main group metals usually form cations whose charge is equal to the group number.
ANSWER: 2 1 0 +1 +2 +3 +4
ANSWER:
Correct All of the elements in group 2 form ions with a +2 charge. That is because all of these elements need to lose two electrons to gain stability. After losing the electrons, there is an excess of two protons, which results in a +2 charge.
Part D Write the formula for the compound lead(II) phosphate. Express your answer as a chemical formula.
Hint 1. How to approach the problem The oxidation number of the cation is given. The anion is polyatomic, so you will have to look up its formula and charge. Because this is a neutral ionic compound, the positive charges must equal the negative charges. Reduce the subscript on each ion to its lowest whole number ratio.
Hint 2. Determine the formula for the phosphate ion What is the formula for the phosphate anion?
Hint 1. How to approach the problem The phosphate ion is an oxoanion composed of two elements: phosphorus and oxygen. Consider that a similar ion, the phosphite ion, has the formula .
ANSWER:
Hint 3. Balance the charges Lead(II) has a charge of +2 and phosphate has a charge of
3. Therefore, the lead(II) phosphate formula must have _____ lead(II) ions and
_____ phosphate ions for the charges to balance.
Hint 1. Charges in neutral compounds Because this is a neutral ionic compound, the total number of positive charges [from the lead(II) ion] must equal the total number of negative charges (from the phosphate ion). The lead(II) ion has a +2 charge and the phosphate ion has a 3 charge. Therefore, if there were only one lead(II) ion and one phosphate ion, the overall charge would be
1, because
. To have an overall charge of 0, this compound will have
more than one of each ion. That is, both ions—iron(II) and chloride—will have subscripts.
ANSWER: one / one one / two one / three two / one two / three three / two
ANSWER:
Correct Lead, like iron, has more than one oxidation state, so it is necessary to put the oxidation state of the metal in brackets. Elements in group 1 and 2 only have one oxidation state and so there is no need for Roman numerals in their systematic name.
Question 3 The coefficients in a balanced chemical equation provide the mole-to-mole stoichiometry among the reactants and products. The molar mass (in can be used as the conversion factor between moles and the mass of a substance. Thus, the balanced equation and molar masses can be used in conjunction with one another to calculate the masses involved in a reaction.
Complete combustion of methane When methane (
) burns, it reacts with oxygen gas to produce carbon dioxide and water. The unbalanced equation for this reaction is
This type of reaction is referred to as a complete combustion reaction.
Part A
)
What coefficients are needed to balance the equation for the complete combustion of methane? Enter the coefficients in the order
,
,
, and
, respectively. Express your answer as four integers, separated by commas (e.g., 1,2,3,4).
Hint 1. How to approach the problem First, balance the carbon atoms. Second, balance the hydrogen atoms. Third, balance the oxygen atoms. Finally, double check that all atoms are balanced.
ANSWER: 1,2,1,2
Correct The balanced chemical equation is therefore:
Part B What mass of carbon dioxide is produced from the complete combustion of 4.70!10"3 of methane? Express your answer numerically in grams.
Hint 1. How to approach the problem First, convert the mass of methane to moles. Then, use the balanced equation to convert moles of methane to moles of carbon dioxide. Finally, convert moles of carbon dioxide to grams.
Hint 2. Determine the number of moles of methane How many moles of methane are in 4.70!10"3 ? Express your answer numerically in moles.
Hint 1. Determine the molar mass of methane What is the molar mass of methane,
? Use the periodic table as needed.
Express your answer numerically in grams per mole. ANSWER: 16.0
ANSWER: 2.93!10"4
Hint 3. Find the number of moles of carbon dioxide How many moles of
are produced from the given amount of
Express your answer numerically in moles.
?
Hint 1. Determine the stoichiometry between methane and carbon dioxide Which of the following would be the correct stoichiometric ratio to convert from moles of methane to moles of carbon dioxide? ANSWER:
ANSWER: 2.93!10"4
Hint 4. Determine the molar mass of carbon dioxide What is the molar mass of carbon dioxide? Use the periodic table as needed. Express your numerically in grams per mole. ANSWER: 44.0
ANSWER: 1.29!10"2
Correct
Part C What mass of water is produced from the complete combustion of 4.70!10"3 of methane? Express your answer numerically in grams.
Hint 1. How to approach the problem First, convert the mass of methane to moles. Second, use the balanced equation to convert moles of methane to moles of water. Finally, convert moles of water to grams of water.
Hint 2. Find the number of moles of water How many moles of
are produced from the given amount of
?
Express your answer numerically in moles.
Hint 1. How to approach the problem First, determine the number of moles of methane that react (you should have already figured this out in Part B). Second, determine the
mole ratio of water to methane given in the balanced equation (which you figured out in Part A). Finally, use the mole ratio to convert from moles of methane to moles of water.
Hint 2. Determine the stoichiometry between methane and water Which of the following would be the correct stoichiometric ratio to convert from moles of methane to moles of water? ANSWER:
Correct Use the conversion formula
to convert the given number of moles of methane to the corresponding number of moles of water.
ANSWER: 5.86!10"4
Answer Requested
Hint 3. Determine the molar mass of water What is the molar mass of water? Use the periodic table as needed. Express your answer numerically in grams per mole. ANSWER: 18.0
Answer Requested The molar mass in the form
can be used to convert moles to grams.
ANSWER: 1.06!10"2
Answer Requested
Part D What mass of oxygen is needed for the complete combustion of 4.70!10"3 of methane? Express your answer numerically in grams.
Hint 1. How to approach the problem First, convert the mass of methane to moles. Second, use the balanced equation to convert moles of methane to moles of oxygen. Finally, convert moles of oxygen to grams of oxygen.
Hint 2. Convert to moles of oxygen How many moles of
are needed to react with the given amount of
?
Express your answer numerically in moles.
Hint 1. How to approach the problem First, determine the number of moles of methane that react (you should have already figured this out in Part B). Second, determine the mole ratio of oxygen to methane given in the balanced equation (which you figured out in Part A). Finally, use the mole ratio to convert from moles of methane to moles of oxygen.
Hint 2. Determine the stoichiometry between methane and oxygen Which of the following would be the correct stoichiometric ratio to convert from moles of methane to moles of oxygen? ANSWER:
ANSWER: 5.86!10"4
Hint 3. Determine the molar mass of oxygen What is the molar mass of
? Use the periodic table as needed.
Express your answer in grams per mole. ANSWER: 32.0
ANSWER: 1.88!10"2
Correct
Question 4 A phase diagram is a convenient means of representing the temperature and pressure dependence of a pure substance in a closed system. The typical phase diagram indicates which phase (solid, liquid, or gas) is stable at a given temperature and pressure. Boundaries separate these phase regions. When a boundary line is crossed owing to changes in temperature and/or pressure a phase change occurs.
Part A Identify each of the labeled points (indicated with letters) or changes (indicated with two letters separated by an arrow) shown on the phase diagram.
Match the words in the left-hand column with the appropriate blank in the sentences in the right-hand column.
Hint 1. Identify the regions of the phase diagram Identify which physical state is shown by each of the colored regions labeled with the letters X, Y, and Z on the phase diagram.
Drag each item to the appropriate bin.
Hint 1. Relation of pressure and temperature to phase High pressure and low temperatures tend to favor the condensed phases whereas low pressure and high temperatures tend to favor the gas state. Use the axes on the diagrams to help identify these conditions.
ANSWER:
Hint 2. Define the specific characteristics of the phase diagram Complete the following sentences related to phase diagrams. Match the words in the left-hand column with the appropriate blank in the sentences in the right-hand column. ANSWER:
ANSWER:
Correct
Part B The phase diagram for an organic compound is shown.
What is the normal boiling point of this compound? Express your answer numerically in degrees Celsius.
Hint 1. Definition of normal boiling point The normal boiling of a substance is the temperature required to establish liquid-vapor equilibrium at standard pressure. On a phase diagram, this point occurs where the liquid-vapor line crosses standard pressure.
Hint 2. Identify the value of standard pressure What is the value of standard pressure? Express your answer numerically in atmospheres. ANSWER: standard pressure = 1.00
ANSWER: normal boiling point = 150
Correct
Question 5 The fluorocarbon compound
has a normal boiling point of 47.6
, respectively. The heat of vaporization for the compound is 27.49
. The specific heats of
and
are 0.91
and 0.67
.
Part A Calculate the heat required to convert 73.5 of
from a liquid at 14.60
to a gas at 76.40
.
Express your answer using one decimal place. ANSWER: = 14.4
Correct
Question 6 Chemists often use molarity
, in
, to measure the concentration of solutions. Molarity is a common unit of concentration because the volume
of a liquid is very easy to measure. However, the drawback of using molarity is that volume is a temperature-dependent quantity. As temperature changes, density changes, which affects volume. Volume markings for most laboratory glassware are calibrated for room temperature, about 20 . Fortunately, there are several other ways of expressing concentration that do not involve volume and are therefore temperature independent. A mass of 0.630
of
is dissolved in 525
of water.
Part A Calculate the molality of the salt solution.
Hint 1. Formula for molality By definition
Hint 2. Solute vs. solvent In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, the solvent is the substance present in the greatest amount.
Hint 3. Determine the number of kilograms of water Convert the mass of water to kilograms. ANSWER:
0.525
ANSWER: 2.05!10"2
Correct
Part B Calculate the mole fraction of salt in this solution.
Hint 1. Formula for mole fraction By definition
Hint 2. Solute vs. solvent In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, the solvent is the substance present in the greatest amount.
Hint 3. Calculate the number of moles of NaCl How many moles of NaCl are in 0.630 ?
Hint 1. Find the molar mass of NaCl What is the molar mass of
?
Express your answer in grams per mole. ANSWER: 58.5
ANSWER: 1.08!10"2
Hint 4. Calculate the number of moles of water How many moles of water are in 525 ?
Hint 1. Find the molecular weight of water What is the molecular weight of water? Express your answer in grams per mole.
Hint 1. Formula for water
The chemical formula for water is
.
ANSWER: 18.0
ANSWER: 29.2
ANSWER: = 3.70!10"4
Correct
Part C Calculate the concentration of the salt solution in percent by mass.
Hint 1. Formula for percent by mass By definition
Hint 2. Solute vs. solvent vs. solution In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, the solvent is the substance present in the greatest amount. The word "solution" refers to solvent plus solute.
Hint 3. Find the mass of the solution What is the mass of this solution? Express your answer five significant figures. ANSWER: 525.63
ANSWER: 0.120 %
g
Correct The total mass of the solution in this case is 525.63 , which makes the percent by mass come to 0.11985617%. However, when rounded to the correct number of significant figures, the answer becomes 0.120%. Quite often, the mass of the solute is so small compared to the mass of the solution that
Part D Calculate the concentration of the salt solution in parts per million
Hint 1. Formula for ppm By definition
Hint 2. Solute vs. solvent vs. solution In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, the solvent is the substance present in the greatest amount. The word "solution" refers to solvent plus solute.
ANSWER: 1200
Correct The word percent means "per 100" (think of century). Therefore, an alternate name for percent by mass could be "parts per hundred." This should help you see the similarity between percent and parts per million:
Question 7 Indicate the type of solute-solvent interaction that should be most important in each of the following solutions.
Part A in benzene ANSWER: dispersion forces dipole-dipole forces ion-dipole forces hydrogen bonding
Correct
Part B methanol
in water
ANSWER: dispersion forces dipole-dipole forces ion-dipole forces hydrogen bonding
Correct
Part C in water ANSWER: dispersion forces dipole-dipole forces ion-dipole forces hydrogen bonding
Correct
Part D in acetonitrile ANSWER: dispersion forces dipole-dipole forces ion-dipole forces hydrogen bonding
Correct
Question 8
By referring to the figure , determine whether the addition of 40.0 solids to 100 of water at 40 will lead to a saturated solution.
Part A
ANSWER: saturated solution unsaturated solution
Correct
Part B
ANSWER: saturated solution unsaturated solution
Correct
Part C
ANSWER: saturated solution unsaturated solution
Correct
Part D
of each of the following ionic
ANSWER: saturated solution unsaturated solution
Correct
Question 9 Ascorbic acid (vitamin C, at 55
) is a water-soluble vitamin. A solution containing 80.5 of ascorbic acid dissolved in 230 of water has a density of 1.22
.
Part A Calculate the mass percentage. ANSWER: 25.9 %
Correct
Part B Calculate the mole fraction. ANSWER: 3.46!10"2
Correct
Part C Calculate the molality. ANSWER: 1.99
Correct
Part D Calculate the molarity of ascorbic acid in this solution. ANSWER: = 1.80
Correct
Question 10 Calculate the number of moles of solute present in each of the following solutions.
Part A 270
of 1.50
ANSWER: = 0.405
Correct
Part B 55.0
of an aqueous solution that is 1.50
ANSWER: = 7.59!10"5
All attempts used; correct answer displayed
Part C 80.0 of an aqueous solution that is 1.70% sucrose (
) by mass
ANSWER: = 3.97!10"3
Correct
Question 11 Part A Calculate the vapor pressure of water above a solution prepared by dissolving 38.0 of glycerin ( pressure of water at 343 ANSWER: = 222
is 233.7
.)
) in 135 of water at 343
. (The vapor
Correct
Part B Calculate the mass of ethylene glycol (
) that must be added to 1.00
. The vapor pressure of pure ethanol at 35
is
of ethanol (
) to reduce its vapor pressure by 12.0
at 35
torr.
ANSWER: = 184
Correct
Question 12 The molar mass of a compound expresses the ratio of mass to moles:
This quantity can be determined experimentally by accurately measuring the mass of the sample and determining the corresponding number of moles based on some property of the sample. Freezing point depression and osmotic pressure measurements are frequently used for this type of determination. In each instance, the number of moles is determined from the colligative property of the solution. For osmotic pressure measurements, the number of moles is calculated from the volume of the solution and the molarity. In freezing point depression measurements, the number of moles is derived from the molality of the solution.
Part A tert-Butyl alcohol is a solvent with a 11.6
of 9.10
of tert-butyl alcohol, the solution froze at 15.3
and a freezing point of 25.5
. When 0.807
of an unknown colorless liquid was dissolved in
.
Which of the following is most likely the identity of this unknown liquid?
Hint 1. How to approach the problem First, calculate the freezing point depression by subtracting the two freezing points: Next, calculate the molality,
, using the equation
Next, convert the mass of solvent to kilograms and use the definition of molality,
to determine the number of moles of solute, Finally, use the mass and number of moles of solute to calculate the molar mass in grams per mole.
Hint 2. Calculate the freezing point depression of the solution What is the value of the freezing point depression,
, of the solution?
Express your answer numerically in degrees Celsius. ANSWER: 10.2
Hint 3. Determine the molality of the solution
What is the molality of the solution? Express the concentration numerically as molality.
Hint 1. What equation to use Based on freezing point depression and the freezing point depression constant of the solvent, the following equation can be solved for molality:
ANSWER: 1.12
Hint 4. Convert the mass of solvent to kilograms What is the mass of the solvent in kilograms? Express the mass numerically in kilograms.
Hint 1. Conversion factor .
ANSWER: 1.16!10"2
Hint 5. Calculate the number of moles of solute present Using the molality and the kilogram mass of the solvent, calculate the number of moles of solute present in the solution. Express your answer numerically in moles. ANSWER: 1.30!10"2
Hint 6. Determine the molar mass of the solute What is the molar mass of the solute used in this experiment? Express your answer numerically in grams per mole.
Hint 1. What equation to use The applicable equation to calculate molar mass is
ANSWER: 62.1
ANSWER:
ethylene glycol (molar mass = 62.07
)
1-octanol (molar mass = 130.22 glycerol (molar mass = 92.09
) )
2-pentanone (molar mass = 86.13
)
1-butanol (molar mass = 74.12
)
Correct
Part B A protein subunit from an enzyme is part of a research study and needs to be characterized. A total of 0.135 of this subunit was dissolved in enough water to produce 2.00 of solution. At 28 the osmotic pressure produced by the solution was 0.138 . What is the molar mass of the protein? Express the molar mass numerically in grams per mole.
Hint 1. How to approach the problem To calculate the molar mass, a mass and the corresponding number of moles must be known. The mass is given in the problem and the number of moles can be calculated from the osmotic pressure. First, convert the temperature to kelvins and solve for molarity using the equation
where
. Next, convert the volume of solution to liters and use the definition of molarity,
to find the moles of solute. Finally, use the mass and number of moles of solute to calculate the molar mass.
Hint 2. Calculate the temperature in kelvins What is the temperature when converted to the Kelvin scale? Express the temperature in kelvins ANSWER: 301
Hint 3. Calculate the molarity of the solution Based on the osmotic pressure, what is the molarity of the protein solution? Express the concentration numerically in molar.
Hint 1. What equation to use Solve the following equation for the molarity:
ANSWER: 5.59!10"3
Hint 4. Convert the volume of the solution to liters
What is the volume of the protein solution in liters? Express the volume numerically in liters.
Hint 1. Conversion factor .
ANSWER: 2.00!10"3
Hint 5. Determine the number of moles of solute in the solution How many moles of solute are present in the protein solution? Express your answer numerically in moles.
Hint 1. What equation to use Solve the following equation for moles of solute:
ANSWER: 1.12!10"5
ANSWER: 1.21!104
Correct
Question 13 Part A List the following aqueous solutions in order of decreasing boiling point. 0.120 Rank items in order of decreasing boiling point. ANSWER:
glucose, 0.050
, 0.050
.
Correct
Question 14 Part A List the following aqueous solutions in order of decreasing freezing point: 0.040
glycerin (
), 0.020
, 0.030
Rank solutions from highest freezing point to lowest freezing point. To rank items as equivalent, overlap them. ANSWER:
phenol (
).
Correct
Question 15 Carbon disulfide
boils at 46.30
and has a density of 1.261
.
Part A When 0.250
of a nondissociating solute is dissolved in 400.0
constant for
?
of
, the solution boils at 47.46
. What is the molal boiling-point-elevation
ANSWER: = 2.34
Correct
Part B When 5.41 of a nondissociating unknown is dissolved in 50.0 unknown? Express your answer using two significant figures. ANSWER: = 260
Correct
Score Summary: Your score on this assignment is 90.9%. You received 13.64 out of a possible total of 15 points.
of
, the solution boils at 47.08
. What is the molecular weight of the
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