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Chapter 18—Chemical Equilibrium
MULTIPLE CHOICE
1. A reaction in which products can react to re-form reactants is
a. at equilibrium.
c. buffered.
b. reversible.
d. impossible.
ANS: B
PTS: 1
DIF: I
OBJ: 18-1.1
5. At equilibrium,
a. the forward reaction rate is lower than the reverse reaction rate.
b. the forward reaction rate is higher than the reverse reaction rate.
c. the forward reaction rate is equal to the reverse reaction rate.
d. no reactions take place.
ANS: C
PTS: 1
DIF: I
OBJ: 18-1.1
6. What symbol in a chemical equation indicates equilibrium?
a.
c.
b.
d. None of the above
ANS: D
PTS: 1
DIF: I
OBJ: 18-1.1
7. Which two processes are at equilibrium in a saturated sugar solution?
a. evaporation and condensation
c. decomposition and synthesis
b. dissolving and crystallization
d. ionization and recombination
ANS: B
PTS: 1
DIF: I
OBJ: 18-1.1
8. At equilibrium, the total amount of the product(s)
a. is always equal to the total amount of the reactants.
b. is always greater than the total amount of the reactants.
c. is always less than the total amount of the reactants.
d. may be equal to, greater than, or less than the total amount of the reactants.
ANS: D
PTS: 1
DIF: I
OBJ: 18-1.1
9. Which symbol represents the equilibrium constant?
a. k
c. c
b. K
d. R
ANS: B
PTS: 1
DIF: I
OBJ: 18-1.2
10. The value of the equilibrium constant for a reaction
a. changes with concentration.
c. changes with temperature.
b. changes with time.
d. is the same under all conditions.
ANS: C
PTS: 1
DIF: I
OBJ: 18-1.2
11. How does the value of K show that a reaction reaches equilibrium very quickly?
a.
b.
c.
d.
K is large.
K is small.
K is zero.
The value of K does not show how quickly a reaction comes to equilibrium.
ANS: D
PTS: 1
13. A very high value of K indicates that
a. equilibrium is reached slowly.
b. products are favored.
ANS: B
PTS: 1
17. In the equation
DIF: I
OBJ: 18-1.2
c. reactants are favored.
d. equilibrium has been reached.
DIF: I
OBJ: 18-1.2
, what represents the concentrations of the reactants?
a. [Y] and [Z]
c.
b. [W] and [X]
d.
ANS: A
PTS: 1
DIF: II
OBJ: 18-1.3
19. How do coefficients from a chemical equilibrium appear when the chemical equilibrium expression is
written?
a. as coefficients
c. as subscripts
b. as exponents
d. They do not appear.
ANS: B
PTS: 1
DIF: I
OBJ: 18-1.3
20. What is the chemical equilibrium expression for the equation
2A2B + 3CD
a.
A4D + C3B2?
c.
b.
ANS: D
d.
PTS: 1
DIF: II
OBJ: 18-1.3
21. An equilibrium mixture of SO2, O2, and SO3 gases at 1500 K is determined to consist of 0.344 mol/L SO2,
0.172 mol/L O2, and 0.56 mol/L SO3. What is the equilibrium constant for the system at this temperature?
The balanced equation for this reaction is
2SO2(g) + O2(g)
a. 0.41
b. 2.8
ANS: D
2SO3(g).
c. 6.7
d. 0.15
PTS: 1
DIF: III
OBJ: 18-1.3
23. If the pressure on the equilibrium system 2CO(g) + O2(g)
a. the quantity of CO(g) increases.
b. the quantity of CO2(g) decreases.
c. the quantity of CO2(g) increases.
d. the quantities in the system do not change.
ANS: C
PTS: 1
2CO2(g) is increased,
DIF: II
25. If the temperature of the equilibrium system CH3OH(g) + 101 kJ
a. [CH3OH] increases and [CO] decreases.
b. [CH3OH] decreases and [CO] increases.
c. [CH3OH] increases and [CO] increases.
d. the concentrations in the system do not change.
ANS: B
PTS: 1
DIF: II
OBJ: 18-2.1
CO(g) + 2H2(g) increases,
OBJ: 18-2.1
27. If more CO(g) is added to the system 2CO(g) + O2(g) 2CO2(g) at constant temperature, K
a. increases.
c. increases or decreases.
b. decreases.
d. does not change.
ANS: D
PTS: 1
DIF: II
OBJ: 18-2.1
29. If a reaction system has come to equilibrium, it can be made to run to completion
a. only if it is not reversible.
c. by applying Le Châtelier's principle.
b. only if the temperature is low enough.
d. under no circumstances.
ANS: C
PTS: 1
DIF: I
OBJ: 18-2.2
31. Reactions tend to run to completion if a product
a. has a high melting point.
c. is precipitated as a solid.
b. is a liquid.
d. is ionic.
ANS: C
PTS: 1
DIF: I
OBJ: 18-2.2
46. What is the equilibrium constant, K, for the ionization of acetic acid, shown in the reaction
CH3COOH(aq) + H2O(l) H3O+(aq) + CH3COOH–(aq)?
a. [H3O+] [CH3COOH–]
c.
b.
ANS: B
d.
PTS: 1
DIF: II
OBJ: 18-3.1
50. What is the equation for the ionization of water?
a. 2H2O(l) H3O+(aq) + OH–(aq)
b. 2H2O(l) H3O–(aq) + OH+(aq)
c. 2H2O(l) 2H2(g) + O2(g)
d. H2O(l) H–(aq) + OH+(aq)
ANS: A
PTS: 1
DIF: I
OBJ: 18-3.2
51. To what degree does water ionize?
a. completely
b. to a large extent
ANS: C
PTS: 1
c. slightly
d. not at all
DIF: I
OBJ: 18-3.2