CHM 2046C Module 10 Chapter 16 Multiple Choice Sample Test#2
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1. If the system, H₃NBF₃(s) <--> NH₃(g) + BF₃(g), is at equilibrium at constant temperature, and the number of moles of H₃NBF₃ in the vessel is doubled then

a.	the equilibrium amount of NH3 and BF3 is increased.
b.	the amount of NH3 and BF3 is doubled.
c.	the partial pressure of both NH3 and BF3 increases until equilibrium is reached.
d.	the amount of H3NBF3 will then start decreasing.
e.	the partial pressure of NH3 and BF3 will remain the same.

2. A mixture of NO and O₂ at a fixed temperature reacts according to the equation, 2NO(g) + O₂(g) <--> 2NO₂(g). When equilibrium is reached, which of the following ratios would be constant regardless of the initial concentrations of NO and O₂?

a.
b.
c.
d.
e.

3. If K = 0.145 for A₂ + 2B <--> 2 AB, then for AB <--> B + 1/2 A₂, K would equal

a.	0.145.
b.	-0.145.
c.	0.381.
d.	2.63.
e.	6.90.

4. Given the equilibrium constants for the following equilibria at 25°C:

The equilibrium constant for the reaction, H₂S(aq) <--> 2H⁺(aq) + S^2-(aq) is

a.	8.3 x 10^5.
b.	9.3 x 10^5.
c.	1.2 x 10^6.
d.	2.2 x 10^-20.
e.	1.2 x 10^-20.

5. For which of the following equilibria would K_c = K_p?

a.	CaCO3(s) <--> CaO(s) + CO2(g)
b.	2H2(g) + O2(g) <--> 2H2O(g)
c.	2NO2(g) <--> N2O4(g)
d.	2NO(g) + O2(g) <--> 2NO2(g)
e.	O3(g) + NO(g) <--> NO2(g) + O2(g)

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6. For the reaction system, N₂O₄(g) <--> 2NO₂(g) at 90°C, K_c = 0.27. For this system, K_p is

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a.	> 0.27.
b.	< 0.27.
c.	= 0.27.
d.	Cannot determine without additional data.

7. A state of dynamic equilibrium exists at constant temperature in

1. an open pan of boiling water.
2. a stoppered flask half full of water.
3. a stoppered flask half full of a saturated solution of sodium chloride containing excess NaCl(s).

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

8. For the following reaction systems at 500 K

1. 2NO(g) + Cl₂(g) <--> 2NOCl(g)      K = 5.9 x 10¹
2. 2NO(g) + O₂(g) <--> 2NO₂(g)      K = 1.7 x 10⁴
3. 2SO₂(g) + O₂(g) <--> 2SO₃(g)      K = 7.7 x 10⁴

the reactions' tendency to go to completion increases in the order

a.	1 < 2 < 3.
b.	3 < 2 < 1.
c.	2 < 1 < 3.
d.	2 < 3 < 1.
e.	3 < 1 < 2.

9. The equilibrium expression for Fe(OH)₃ is

a.	[Fe^3+][3OH^-]^3.
b.	[Fe^2+][OH^-]^3.
c.	[Fe^3+][OH^-]^3.
d.	[Fe][OH]^3.
e.	[Fe^3+][OH^-].

10. Which of the following 1:1 electrolytes is the next to most soluble?

a.	BaCO3; K = 8.1 x 10^-9
b.	CaCO3; K = 3.8 x 10^-9
c.	CuCl; K = 1.9 x 10^-7
d.	BaSO3; K = 8.0 x 10^-7
e.	CaCrO4; K = 7.1 x 10^-4

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11. At 30°C, an equilibrium mixture of NO₂(g) and N₂O₄(g) exerted a total pressure of 0.750 atm. The partial pressure of N₂O₄ was 0.500 atm. K_p for the reaction 2NO₂(g) <--> N₂O₄(g) is

a.	8.00.
b.	2.00.
c.	0.500.
d.	0.250.
e.	0.125.

12. The reaction of nitrogen with hydrogen to produce ammonia is represented by the following equilibrium:
N₂(g) + 3H₂(g) <--> 2NH₃(g)
at 750 K, K_c = 0.010. If the concentration of NH₃ is 10^-3 M and N₂ is 0.10 M, then the concentration of H₂ is

a.	1.0 M.
b.	0.10 M.
c.	0.010 M.
d.	0.0010 M.
e.	0.00010 M.

13. At 425°C, a 1.00 L vessel contained 0.100 moles of I₂ 0.100 moles of H₂, and 0.700 moles of HI in equilibrium. K_c for the reaction, H₂(g) + I₂(g) <--> 2HI(g), is

a.	70.0.
b.	49.0.
c.	14.0.
d.	6.90.
e.	2.70.

14. Dinitrogen tetroxide readily undergoes decomposition to form red-brown NO₂(g) as represented by the equation N₂O₄(g) <--> 2NO₂(g). At 25°C, 0.11 mole of N₂O₄ reacts to form 0.10 mole of N₂O₄ and 0.02 mole of NO₂. At 90°C, 0.11 mole of N₂O₄ forms 0.050 mole of N₂O₄ and 0.12 mole of NO₂. From these data we can conclude

a.	N2O4 molecules react by a second order rate law.
b.	N2O4 molecules react by a first order rate law.
c.	the reaction above is exothermic.
d.	N2O4 molecules react faster at 25°C than at 90°C.
e.	the equilibrium constant for the reaction above increases with an increase in temperature.

15. For the equilibrium

K equals 1.6 at 1260 K. If 0.20 mol each of H₂O, CO, H₂, and CO₂ (all at 1260 K) were placed in a 1.0 L thermally insulated vessel which was also at 1260 K, the reaction quotient would have the value of ______ and there would be a net ______ in products and a(n) ______ in the temperature

a.	1; increase; increase
b.	1; decrease; decrease
c.	1; increase; decrease
d.	1; decrease; increase
e.	1.6; none; none

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Question Instructions: This question refers to the following equilibrium at a given temperature:
4NH₃(g) + 3O₂(g) <--> 2N₂(g) + 6H₂O(g)

16. Suppose the equilibrium above were established by adding 0.30 mole of NH₃ and 0.40 mole of oxygen to a 5.0 l container. If y moles of water are present at equilibrium, then the number of moles of ammonia remaining at equilibrium would be

a.	0.30 - y.
b.	0.40 - 3/2 y.
c.	4/6 y.
d.	0.30 - 3/2 y.
e.	0.30 - 2/3 y.

Question Instructions: This question refers to the following equilibrium at a given temperature:
4NH₃(g) + 3O₂(g) <--> 2N₂(g) + 6H₂O(g)

17. Under the conditions above, the equilibrium concentration of oxygen will be

a.	0.40 - 0.50 y.
b.	0.30 - 0.50 y.
c.	0.08 - 0.10 y.
d.	0.06 - 0.13 y.
e.	0.40 - 3/2 y.

18. Which of the following equilibria would not be affected by volume changes at constant temperature?

a.	2CO(g) + O2(g) <--> 2CO2(g)
b.	2NO2(g) <--> N2O4(g)
c.	2NO(g) + 3F2(g) <--> 2F3NO(g)
d.	BF3(g) + NH3(g) <--> H3NBF3(s)
e.	O3(g) + NO(g) <--> NO2(g) + O2(g)

19. In which of the following reactions does an instantaneous increase in the volume of the reaction vessel favor formation of the products?

a.	CO(g) + Cl2(g) <--> COCl2(g)
b.	PF3Cl2(g) <--> PF3(g) + Cl2(g)
c.	H2(g) + I2(g) <--> 2HI(g)
d.	N2(g) + O2(g) <--> 2NO(g)
e.	N2(g) + 3H2(g) <--> 2NH3(g)

20. Solid HgO, liquid Hg, and gaseous O₂ are placed in a glass bulb and are allowed to reach equilibrium at a given temperature.
2HgO(s) <--> 2Hg(l) + O₂(g) DH = 43.4 kcal
The mass of HgO in the bulb could be increased by

a.	adding more Hg.
b.	removing some O2.
c.	reducing the volume of the bulb.
d.	increasing the temperature.
e.	removing some Hg.

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21. Consider the reaction system
2BrCl(g) <--> Br₂(g) + Cl₂(g)
at a given temperature. When the system is at equilibrium, the molar concentrations of BrCl, Br₂, and Cl₂ are 0.015 M, 0.0095 M, and 0.0060 M respectively. The value of K for this system is

a.	0.25.
b.	3.9.
c.	27.
d.	53.
e.	260.

22. For the reaction system
H₂(g) + I₂(g) <--> 2HI(g)
K = 50. at 720 K. If the initial concentrations of HI, H₂ and I₂ are all 1.0 x 10^-3 M, which one of the following statements is correct?

a.	The system is at equilibrium.
b.	The concentrations of HI and I2 will increase as the system is approaching equilibrium.
c.	The concentrations of H2 and HI will decrease as the system is approaching equilibrium.
d.	The concentration of HI will increase as the system is approaching equilibrium.
e.	The concentrations of H2 and I2 will increase as the system is approaching equilibrium.

23. For an endothermic reaction, an increase in temperature will

a.	increase the rate but decrease the equilibrium constant.
b.	decrease both the rate and the equilibrium constant.
c.	increase the rate but have no effect on the equilibrium constant.
d.	increase both the rate and the equilibrium constant.
e.	have no effect upon the rate and the equilibrium constant will decrease.

24. Consider the reaction system
2CO(g) <--> C(s) + CO₂(g)     DH = -172 kJ
Which changes will increase the quantity of CO?

1. Adding fine mesh carbon.
2. Decreasing the volume of the reaction system.
3. Increasing the temperature.

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

25. Consider the reaction system where DH = -114 kJ
2NO(g) + O₂(g) <--> 2NO₂(g)
The conditions which would favor maximum conversion of the reactants to products would be

a.	high temperature and high pressure.
b.	high temperature and pressure unimportant.
c.	high temperature and low pressure.
d.	low temperature and low pressure.
e.	low temperature and high pressure.

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