Chemistry Practice Exam v2 and Answers (study guide 2022) score Grade A
Directions: It is important that you provide answers in your own words. Please focus only on
information from the text/eBook to create your own solutions. Please do not use direct information
from an outside source (especially copying and pasting from an “answer” website). Use of direct
information from an outside source is against school policy. All answers will be checked for plagiarism.
Instances of plagiarism can result in probation or possible dismissal from the school.
Please be sure to follow all guidelines (number of sentences/showing all calculations) and to provide the
correct metric units of measure. All questions are 3.33 points each (.33 for unit)
1. A student collected the following data for a fixed volume of gas:
Temperature (⁰C) Pressure (mm of Hg)
10 726
20 750
40 800
70 880
100 960
150 1085
Fill in the missing data point. Show all calculations leading to an answer.
The General Law of Gases states that
P1*V1/T1 = P2*V2/T2.
As Volume is constant, we can write this as
P1/T1 = P2/T2,
P1 and T1 are the pressure and temperature at time 1.
P2 and T2 are the pressure and temperature at time 2.
You can take any pair of values as P1 and T1 and find P2 = P1T2/T1, once you sum 273.15 to each
temperature to get kelvins.
P1 = 726 mm Hg
T1 = 10 + 273.15 = 283.15 K;
T2 = 150 + 273.15 = 423.15 K.
Then, P2 = 726 * 423.15/283.15 = 1085.96 mm Hg.
2. You are given a clear solution of KNO3. Using 3 – 4 sentences (in your own words) explain how
you would determine if the solution is unsaturated, saturated or supersaturated.
By adding more solute to KNO3. If the solute added still dissolves in the solution, then the solution is
unsaturated. If the addition of more solute in the solution makes the extra solute not to dissolve, then
, the solution is saturated. However, when precipitation occurs with addition of more solute, then it is
supersaturated.
3. Explain why gasoline will not dissolve in water.
Gasoline is a non-polar compound hence cannot dissolve in water which is a polar substance hence can
form bonds with substances which have ionic properties.
4. Explain in 3 – 4 sentences (in your own words) how perspiration helps keep you cool on a hot
day.
Perspiration facilitates the removal of excess heat generated by the body during the metabolic
processes. The excess heat removed results in removal of latent heat of vaporization from the
body when it escapes into the atmosphere leading to cooling effect on the body.
5. You have two sealed jars of water at the same temperature. In the first jar there is a large
amount of water. In the second jar there is a small amount of water. Using 3 -4 sentences
explain how the vapor pressure of water in the first jar compares with the vapor pressure of
water in the second jar.
They are the same. The vapor pressure of water is only dependent on temperature. The amount of water
does not affect it. Since there is no alteration of the temperature of the two jars filled with water, the
vapor pressure is the same in all the jars.
6. Using 3 – 4 sentences explain (in your own words) why water expands when it freezes?
The hydrogen bond forms a crystalline structure that decreases the density since each water molecule is
held from the each other at a distance that is equal to the length of the hydrogen bond. Hence, water
expands as it freezes.
7. Using your knowledge of colligative properties explain whether sodium chloride or calcium
chloride would be a more effective substance to melt the ice on a slick sidewalk. Use 3 – 4
sentences in your explanation.
Calcium chloride is better at melting ice than sodium chloride (assuming equal moles per kg of water).
For starters, the dissolving of CaCl2 is exothermic which releases some heat that NaCl does not, and
helps melt ice. In addition, for each formula unit of CaCl2 there are three particles (van't Hoff factor, i, is
3). For NaCl i = 2.
Directions: It is important that you provide answers in your own words. Please focus only on
information from the text/eBook to create your own solutions. Please do not use direct information
from an outside source (especially copying and pasting from an “answer” website). Use of direct
information from an outside source is against school policy. All answers will be checked for plagiarism.
Instances of plagiarism can result in probation or possible dismissal from the school.
Please be sure to follow all guidelines (number of sentences/showing all calculations) and to provide the
correct metric units of measure. All questions are 3.33 points each (.33 for unit)
1. A student collected the following data for a fixed volume of gas:
Temperature (⁰C) Pressure (mm of Hg)
10 726
20 750
40 800
70 880
100 960
150 1085
Fill in the missing data point. Show all calculations leading to an answer.
The General Law of Gases states that
P1*V1/T1 = P2*V2/T2.
As Volume is constant, we can write this as
P1/T1 = P2/T2,
P1 and T1 are the pressure and temperature at time 1.
P2 and T2 are the pressure and temperature at time 2.
You can take any pair of values as P1 and T1 and find P2 = P1T2/T1, once you sum 273.15 to each
temperature to get kelvins.
P1 = 726 mm Hg
T1 = 10 + 273.15 = 283.15 K;
T2 = 150 + 273.15 = 423.15 K.
Then, P2 = 726 * 423.15/283.15 = 1085.96 mm Hg.
2. You are given a clear solution of KNO3. Using 3 – 4 sentences (in your own words) explain how
you would determine if the solution is unsaturated, saturated or supersaturated.
By adding more solute to KNO3. If the solute added still dissolves in the solution, then the solution is
unsaturated. If the addition of more solute in the solution makes the extra solute not to dissolve, then
, the solution is saturated. However, when precipitation occurs with addition of more solute, then it is
supersaturated.
3. Explain why gasoline will not dissolve in water.
Gasoline is a non-polar compound hence cannot dissolve in water which is a polar substance hence can
form bonds with substances which have ionic properties.
4. Explain in 3 – 4 sentences (in your own words) how perspiration helps keep you cool on a hot
day.
Perspiration facilitates the removal of excess heat generated by the body during the metabolic
processes. The excess heat removed results in removal of latent heat of vaporization from the
body when it escapes into the atmosphere leading to cooling effect on the body.
5. You have two sealed jars of water at the same temperature. In the first jar there is a large
amount of water. In the second jar there is a small amount of water. Using 3 -4 sentences
explain how the vapor pressure of water in the first jar compares with the vapor pressure of
water in the second jar.
They are the same. The vapor pressure of water is only dependent on temperature. The amount of water
does not affect it. Since there is no alteration of the temperature of the two jars filled with water, the
vapor pressure is the same in all the jars.
6. Using 3 – 4 sentences explain (in your own words) why water expands when it freezes?
The hydrogen bond forms a crystalline structure that decreases the density since each water molecule is
held from the each other at a distance that is equal to the length of the hydrogen bond. Hence, water
expands as it freezes.
7. Using your knowledge of colligative properties explain whether sodium chloride or calcium
chloride would be a more effective substance to melt the ice on a slick sidewalk. Use 3 – 4
sentences in your explanation.
Calcium chloride is better at melting ice than sodium chloride (assuming equal moles per kg of water).
For starters, the dissolving of CaCl2 is exothermic which releases some heat that NaCl does not, and
helps melt ice. In addition, for each formula unit of CaCl2 there are three particles (van't Hoff factor, i, is
3). For NaCl i = 2.
