CHM 2046 Module 8II Chapter 14

Sample Multiple Choice Test#1 Answers

Based on Kotz 5^th Edition

(pages references to 5^th Edition)

1. The correct answer is:
moles of solute per kilogram of solvent.

Explanation:


Solution Reference:
Page 643, Molality

1. The molality of a solution is

a.	moles of solute per liter of solution.
b.	moles of solute per mole of solvent.
c.	moles of solute per liter of solvent.
d.	moles of solute per kilogram of solvent.
e.	moles of solute per kilogram of solution.

2. The correct answer is:
1.00.

Explanation:


Solution Reference:
Page 643, Molality

2. If 0.100 mole of naphthalene is dissolved in 100. g of benzene (C₆H₆), the molality is

a.	0.100.
b.	0.900.
c.	1.00.
d.	1.28.
e.	12.8.

3. The correct answer is:
0.49

Explanation:


Solution Reference:
Page 643 Mole Fraction

3. What is the mole fraction methanol, CH₃OH, in an ethanol, C₂H₅OH, solution that is 60.0% ethanol by mass?

a.	0.40
b.	0.46
c.	0.49
d.	0.54
e.	0.60

4. The correct answer is:
0.500 m.

Explanation:


Solution Reference:
Page 643, Molality

4. The water of hydration becomes part of the solvent. In terms of the anhydrous salt (Al₂(SO₄)₃), the solution has the concentration

a.	0.500 m.
b.	0.600 m.
c.	0.500 M.
d.	0.600 M.
e.	0.400 m.

5. The correct answer is:
8.38%

Explanation:

5. If 32.0 g of NaCl is dissolved in 350. g of H₂O, what is the percent by weight (by mass) of NaCl in the solution?

a.	0.0838%
b.	0.0914%
c.	10.7%
d.	9.14%
e.	8.38%

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6. The correct answer is:
1.3.

Explanation:


Solution Reference:
Page 644, Parts Per Million

6. A water sample contains 0.35 mg of arsenic in 275 g of water. The concentration of arsenic in ppm is

a.	1.3.
b.	2.3.
c.	3.5.
d.	7.6.
e.	23.

7. The correct answer is:
0.167

Explanation:


Solution Reference:
Page 643, Molality

7. Calculate the mole fraction of urea (CO(NH₂)₂) that results from mixing 12.0 g of urea with 32.0 g of methanol (CH₃OH).

a.	0.125
b.	0.167
c.	0.375
d.	0.625
e.	0.833

8. The correct answer is:
dissolve in each other.

Explanation:
They mix with each other in all proportions.

Solution Reference:
Page 646, Liquids Dissolving in Liquids

8. Miscible liquids

a.	are polar.
b.	are nonpolar.
c.	are stable.
d.	are unstable.
e.	dissolve in each other.

9. The correct answer is:
3.56 M

Explanation:


Solution Reference:
Page 642, Molarity and Page 644, Weight Percent

9. What is the molarity of 20.0% nitric acid solution, HNO₃(aq) if the density of the solution is 1.12 g/cm³?

a.	3.56 M
b.	3.89 M
c.	4.21 M
d.	4.48 M
e.	4.84 M

10. The correct answer is:
the solubility of the solid will increase with increasing temperature.

Explanation:

From a consideration of LeChatelier's principle, if we exert a stress (increasing the temperature) on the left hand side of the equation by adding heat, it will shift to the right in order to remove the stress.

Solution Reference:
Page 649, Heat of Solution and Page 655, LeChatelier's Principle

10. If the dissolution of an ionic solid in water in endothermic, then it can be concluded that

a.	the solubility of the solid will increase with increasing temperature.
b.	DH is negative.
c.	the solution process releases heat.
d.	the hydration energy exceeds the lattice energy.
e.	the solubility of the solid is independent of the temperature.

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11. The correct answer is:
1 only

Explanation:
Both CCl₄ and C₆H₆ are nonpolar molecules.

Solution Reference:
Page 646, Liquids Dissolving in Liquids

11. Which of the following pairs of liquids are miscible with each other?

a.	1 only
b.	2 only
c.	3 only
d.	1 and 2 only
e.	1, 2, and 3

12. The correct answer is:
atmospheric pressure.

Explanation:
Henry's law is S(g) = kP_g where k is the constant at a given temperature for the gas and P is the partial pressure of the gas. The atmospheric pressure does not enter into this relationship. The constant k depends upon both nature of the gas and of the solvent.

Solution Reference:
Page 653, Henry's Law

12. All of the following affect the solubility of gases in solvents EXCEPT

a.	nature of the gas.
b.	nature of the solvent.
c.	pressure of the gas.
d.	temperature.
e.	atmospheric pressure.

13. The correct answer is:
decrease.

Explanation:
S(g) = kP(g)

Solution Reference:
Page 653, Henry's Law

13. If the pressure of a gas over a liquid decreases, the amount of gas dissolved in the liquid will

a.	increase.
b.	decrease.
c.	remain the same.
d.	depend on the polarity of the solvent.
e.	depend on the polarity of the gas.

14. The correct answer is:
solute solubility.

Explanation:
The solubility of a solute depends upon the nature of the solute. Every solute has its own characteristic solubility. A colligative property is independent of the kind of solute.

Solution Reference:
Page 656, Colligative Properties

14. All of the following are colligative properties of a solution EXCEPT

a.	freezing point depression.
b.	boiling point elevation.
c.	vapor pressure lowering.
d.	osmotic pressure.
e.	solute solubility.

15. The correct answer is:
mole fraction of solvent.

Explanation:
P_solvent = X_solvent P°_solvent

Since a solution consists of a solute and a solvent and the solute is nonvolatile, then the vapor pressure of the solution is simply the vapor pressure of the solvent. The change in vapor pressure, DP_solvent = X_solute P°_solvent is directly proportional to the mole fraction of solute.

15. The vapor pressure of a solution containing a nonvolatile solute is directly proportional to the

a.	mole fraction of solvent.
b.	mole fraction of solute.
c.	molality of the solvent.
d.	molality of the solute.
e.	osmotic pressure of the solute.

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16. The correct answer is:
0.091

Explanation:


Solution Reference:
Page 643, Mole Fraction

16. Consider that an ideal solution is formed from a mixture of the nonvolatile solute, urea (CO(NH₂)₂), and methanol (CH₃OH). The vapor pressure of pure methanol at 20°C is 89 mm Hg. Calculate the mole fraction of urea that is obtained from mixing 6.0 g of urea with 32.0 g of methanol.

a.	0.091
b.	0.10
c.	0.16
d.	0.84
e.	0.91

17. The correct answer is:
8.9 mm Hg

Explanation:
P_solution = X_solvent P°_solvent P_solution = (1.00 = 0.091)(89 mm Hg) = 81 mm Hg

Solution Reference:
Page 656, Raoult's Law

17. Consider that an ideal solution is formed from a mixture of the nonvolatile solute, urea (CO(NH₂)_2,), and methanol (CH₃OH). The vapor pressure of pure methanol at 20?C is 89 mm Hg. Calculate the vapor pressure of the methanol solution in problem No. 16.

a.	8.1 mm Hg
b.	8.9 mm Hg
c.	14 mm Hg
d.	75 mm Hg
e.	81 mm Hg

18. The correct answer is:
8.0 mm Hg

Explanation:
DP = P_solvent - P_solution = 89-81 = 8 mm Hg

Solution Reference:
Page 656, Raoult's Law

18. Consider that an ideal solution is formed from a mixture of the nonvolatile solute, urea (CO(NH₂)₂), and methanol (CH₃OH). The vapor pressure of pure methanol at 20°C is 89 mm Hg. Calculate the vapor pressure-lowering for the methanol solution in problem No. 16.

a.	6.0 mm Hg
b.	8.0 mm Hg
c.	14 mm Hg
d.	75 mm Hg
e.	81 mm Hg

19. The correct answer is:
-0.046°C

Explanation:
DT = K_fm = -1.86°C/m x 0.025 = -0.046°C Freezing point = -0.046°C

Solution Reference:
Page 662, Colligative Properties and Molar Mass Determination

19. The freezing point of a 0.025 m solution of formaldehyde (CH₂O) in water would be (K_f for water is -1.86°C/m).

a.	-1.86°C
b.	-0.046°C
c.	0.046°C
d.	0.093°C
e.	-0.093°C

20. The correct answer is:
0.12.

Explanation:


Solution Reference:
Page 662, Colligative Properties and Molar Mass Determination

20. The freezing point of an aqueous solution of a nonelectrolyte is -0.23°C. The molality of this solution is (K_f(H₂O) = -1.86°C/m)

a.	0.12.
b.	0.25.
c.	0.45.
d.	0.51.
e.	1.86.

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21. The correct answer is:
26.8.

Explanation:


Solution Reference:
Page 129, Empirical Formulas

21. A compound containing boron, nitrogen, and hydrogen analyzes 40.3% B, 52.2% N, and 7.5% H. A 3.562 g sample of this compound was dissolved in 50.00 g of benzene producing a solution freezing at 1.3°C. K_f for benzene is -5.12°C/molal. Pure benzene has a freezing point of 5.48°C. Determine the empirical formula of the compound from the percentage composition. The empirical weight of the B, N, H compound is

a.	25.8.
b.	26.8.
c.	50.6.
d.	51.6.
e.	106.

22. The correct answer is:
0.82.

Explanation:


Solution Reference:
Page 643, Molality

22. A compound containing boron, nitrogen, and hydrogen analyzes 40.3% B, 52.2% N, and 7.5% H. A 3.562 g sample of this compound was dissolved in 50.00 g of benzene producing a solution freezing at 1.3°C. K_f for benzene is -5.12°C/molal. Pure benzene has a freezing point of 5.48°C. The molality of the benzene solution is

a.	0.071.
b.	0.24.
c.	0.70.
d.	0.82.
e.	1.07

23. The correct answer is:
87.

Explanation:


Solution Reference:
Page 662, Molar Mass Determination

23. A compound containing boron, nitrogen, and hydrogen analyzes 40.3% B, 52.2% N, and 7.5% H. A 3.562 g sample of this compound was dissolved in 50.00 g of benzene producing a solution freezing at 1.3°C. K_f for benzene is -5.12°C/molal. Pure benzene has a freezing point of 5.48°C. The experimental molecular weight for the compound is

a.	67.
b.	87.
c.	102.
d.	106.
e.	297.

24. The correct answer is:
B₃N₃H₆.

Explanation:


Solution Reference:
Page 129, Molecular Formula

24. A compound containing boron, nitrogen, and hydrogen analyzes 40.3% B, 52.2% N, and 7.5% H. A 3.562 g sample of this compound was dissolved in 50.00 g of benzene producing a solution freezing at 1.3°C. K_f for benzene is -5.12°C/molal. Pure benzene has a freezing point of 5.48°C. The molecular formula for the compound is

a.	B2N2H.
b.	B4N4H2.
c.	BNH2.
d.	B3N3H6.
e.	B4N4H8.

25. The correct answer is:
5

Explanation:
How many ions are there in one formula unit of Al₂(SO₄)₃?

Solution Reference:
Page 667, van't Hoff Factor

25. For a 0.001 molal solution of Al₂(SO₄)₃, the van't Hoff factor, i, would be about

a.	1
b.	2
c.	3
d.	4
e.	5

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