HCCS CHEM 1405
PRACTICE EXAM III (Ch. 5 – 6)
Multiple Choice: Choose the best answer. Key is highlighted in bold characters.
1.
Which of the following is a wrong statement about the gas laws?
A)Breathing illustrates Boyle’s law.
B) Charles’ law illustrates that the volume of gas expands when temperature becomes higher.
C) Avogadro’s law illustrates that the volume of gas is proportional to its mole number or say its
quantity or amount.
D) Gay-Lussac’s law illustrates that the pressure of gas is proportion to its temperature.
E) All of the above are correct statements.
Hint: Comprehensive: definition: p.p. 124-135.
2.
When 6.0 mol of oxygen are confined in a 36-L vessel at 196oC, the pressure is 8 atm. What is the
new pressure for oxygen expands at constant temperature to fill 48 L?
A) 6 atm
B) 8 atm
C) 12 atm
D) 16 atm
Hint: p.p. 126-129: example & problem 5.2 & 5.3. Boyle’s law: P 1V1 = P2V2.
3.
A gas sample of argon, maintained at constant temperature, occupies a volume of 500 L at 4.00
atm. What is the new volume if the pressure were charged to 8 atm?
A)500 L
B) 250 L
C) 125 L
D) 62.5 L
Hint: p.p. 126-129: example & problem 5.2 & 5.3. Boyle’s law: P 1V1 = P2V2.
4.
What is the resulting temperature of the gas if 200 mL of a gas sample at 27 oC expands to 500
mL?
A) 750 K
B) 477 oC
C) 890.6 oF
D) All of the above
Hint: p.p. 129-131: example & problem 5.4 & 5.5. Note: you must convert oC to K in order to plug
into Charles’s law: T1/V1 = T2/V2.
5.
A sample of hydrogen gas in a closed container has a temperature of 37oC and a pressure of 2 atm.
What will be the pressure if the sample is heated to 127 oC? Note: you must convert oC to K in
order to plug into the gas law.
A) 2.58 atm
B) 3.47 atm
C) 5.21 atm
D) 6.77 atm
Hint: p.p. 131-134: example & problem 5.6 & 5.7. Note: you must convert oC to K in order to plug
into Gay-Lussac’s law: T1/P1 = T2/P2.
6.
A gas under 25 atm pressure occupies 35.0 L at 127 oC. What is the volume of the gas under
standard conditions (1 atm, 0oC)?
A) 0 L
B) 597.2 L
C) 1880.9 L
D) 3000 L
Hint: p.p. 135-136: example & problem 5.8. Note: you must convert oC to K in order to plug into
the combined gas law: P1V1/T1 = P2V2/T2.
7.
A sample of gas has a volume of 0.600 L at a temperature of 30 oC and a pressure of 0.8 atm.
What is the number of moles in this sample?
A) 0.2
B) 0.02
C) 14.4
D) 145.4
Hint: p.p. 136-137: example & problem 5.9. Note: you must convert oC to K in order to plug into
the ideal gas law: PV = nRT.
8.
A gas has a density of 3.84 g/L at a pressure of 3.50 atm and a temperature of 37oC. What is the
molar mass (g/mol) of this gas?
A) 27.89
B) 0.102
C) 497.28
D) 58.73
Hint: p.p. 137-138: example & problem 5.10 & 5.11. Note: you must convert oC to K in order to
plug into the gas law: PM = dRT.
9. A mixture of 1.25 mol of argon and 3.75 mol nitrogen is prepared in a container
such that the total pressure is 760torr. Calculate the partial pressure of argon.
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10. Which of the following compounds condense to the liquid phase from the gas phase through polar
secondary forces?
A) H2
B) CCl4
C) HCN
D) I2
Hint: p.p. 151-152 example 6.1. Note that change “non-polar” of problem 6.1 to “polar”, otherwise the
answer provided in P-2 of the textbook is wrong. Also the concept is in your lab titled “polar and nonpolar”. You must consider the molecular geometry or molecular shape in addition to bond polarity.
This is because a molecule containing polar bond does not guarantee it to be a polar molecule. For
instance, B-F bond in BF3 is polar as the electronegativity difference between B (electronegativity is
2.0) and F (electronegativity is 4.0) is 4.0 –2.0 = 2.0 > 0.5 and thus the B-F bond is polar. Since the
molecular geometry of BF3 is trigonal planar(see VSEPR model in chapter 3) and thus BF3 is a nonpolar molecule.
11.
12. Which of the following statements is wrong in consideration of molecular packing among three
states of matter?
A) Gas molecules are packed loosely.
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B) Solid molecules are packed as closely together as possible.
C) Liquid molecules are in-between the gas and solid molecules.
D) All of the above statements are correct.
Hint: p.p. 149-150. Definition/fact.
13. Which of the following definition is wrong?
A) The amount of heat required to transform a liquid into a gas is called molar heat of
vaporization.
B) The amount of heat required to melt a solid is called molar heat of fusion.
C) The temperature at which a solid melts is called melting point.
D) All of the above are correct.
Hint: p.p. 149-151. Definition.
14. Which of the following definition is wrong?
A) The temperature at which a liquid boils at 1 atm is called normal boiling point.
B) The temperature at which a liquid freezes is called freezing point.
C) The melting point and freezing point for a substance are actually the same.
D) None of the above is wrong.
Hint: Given a definition and then make a conclusion. You may want to look at a heating curve.
Hint: p.p. 149-151. Definition.
15. As a solid is heated, its temperature increases from 27 oC to 57oC, remains at 57oC for 5 minutes,
and then increases to beyond 77oC. What is the melting point of this solid?
A) 27oC
B) 57oC
C) 77oC.
D) 30oC
Hint: p.p. 149-151.
16. Non-polar substances will condense mainly because of
A) London forces.
B) Ion-dipole interaction.
C) Dipole-dipole interaction.
D) Hydrogen bonding.
Hint: p.p. 151-153. Definition.
17. Hydrogen bonding or hydrogen bonds can form when hydrogen bonds to
A) Nitrogen.
B) Oxygen.
C) Fluorine.
D) All of the above.
Hint: p.p. 153-155: Table 6.2, example & problem 6.2. Definition.
18. Which of the following has the highest boiling point because it has the greatest hydrogen bonding?
A) H2O
B) HF
C) HCl
D) NH3
Hint: p.p. 155-157: Table 6.3, example & problem 6.3. Note that all molecules in A), B), C, and
D) have hydrogen bonding. The more hydrogen bonding a molecule has, the higher boiling and
melting points that molecule possesses.
19. Which of the following pairs of common molecules do not have Hydrogen bonding present?
A) H2O and HF
B) HCl and CH3OH
C) C2H5OH and NH3
D) None of the above.
Hint: p.p. 153-155: Tables 6.1 & 6.3, example & problem 6.2, 6.3 & 6.8. Memorization.
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20. Boiling point increases with increasing molar mass. However, the one with hydrogen bonding will
have higher boiling point, and that more hydrogen bonds the greater the boiling point. Which is
correct for the increasing order of boiling point?
A) H2 < N2 < O2 < F2 < NH3 < H2O
B) H2 > N2 > O2 > F2 > NH3 > H2O
C) N2 < H2O < O2 < H2 < F2 < NH3
D) N2 > H2O > O2 > H2 > F2 > NH3
Hint: p.p. 151-157: Table 6.2, example & problem 6.2, 6.3 & 6.8. Application of Q 34. Same
concept. Note that the question does give you the hint written in italic characters.
21. Water can be made to boil at 110 oC by increasing pressure with volume constant. Which of the
following procedure can make water be boiled at 80 oC?
A) Decreasing pressure with volume constant.
B) Decreasing pressure with volume increasing.
C) Increasing pressure with volume decreasing.
D) Increasing pressure with volume increasing.
Hint: p. 164: Figure 6.12, same concepts as example & problem 6.6 & 6.7. Common sense or by
applying the ideal gas equation: PV = nRT, indicating that P is proportional to T. Note that the
question does give you the hint written in italic characters
22. What is the vapor pressure for a liquid at its normal boiling temperature?
A) 760 mm Hg
B) 76 cm Hg
C) 1 atm
D) All of the above.
Hint: p. 122: example & problem 5.1.
23. In hydrocarbons (non-polar compounds), the one with the lowest molar mass has the lowest
melting and boiling point; while the one with the highest molar mass has the highest boiling point.
Which of the following is a correct order of decreasing (from highest to lowest) melting and
boiling point?
A) CH4 < C2H6 < C3H8 < C4H10 < C5H12
B) CH4 > C2H6 > C3H8 > C4H10 > C5H12
C) C5H12 < CH4 < C2H6 < C4H10 < C3H8
D) C5H12 > C4H10 > C3H8 > C2H6 > CH4
Hint: p. 169: same concept as example & problem 6.9. Note that the question does give you the
hint written in italic characters
24. Solid magnesium chloride is an example of an ionic crystal. As magnesium chloride is an ionic
compound and it is a solid. Which of the following statement is true?
A) Sugar is an ionic compound and it is a solid.
B) Potassium chloride is a molecular compound and it is a solid.
C) Sulfuric acid is a molecular compound and it is a liquid.
D) Sodium chloride is an ionic compound and it is a gas.
Hint: p. 169. Definition.
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