Chapter 14 2 Gaseous hydrogen bromide decomposes at elevated temperatures

Unlock access to all the studying documents.

View Full Document

53) Gaseous hydrogen bromide decomposes at elevated temperatures according to the following

equation:

At a certain temperature a 2.00 L flask is initially filled only with 0.600 mol of HBr. What is the value of

Kc at that temperature if the flask contains 0.104 mol of H2 at equilibrium?

A) 7.04 × 10-2

B) 4.40 × 10-2

C) 3.00 × 10-2

D) 2.10 × 10-1

54) When reaction (1) and (2) below are added together, the result is reaction (3).

1) H2O(l) + HNO2(aq) ⇌ H3O+(aq) + NO2–(aq)

2) H3O+(aq) + OH–(aq) ⇌ 2 H2O(l)

3) HNO2(aq) + OH–(aq) ⇌ NO2–(aq) + H2O(l)

If K1 = 4.50 × 10-4, and K2 = 1.00 × 1014, find the equilibrium constant, K3.

A) 4.50 × 10–18

B) 4.50 × 1010

C) 1.00 × 1014

D) 2.22 × 1017

55) Oxalic acid can donate two protons to water in successive reactions:

(1) H2C2O4(aq) + H2O(l) ⇌ H3O+(aq) + HC2O4–(aq)

(2) HC2O4–(aq) + H2O(l) ⇌ H3O+(aq) + C2O42-(aq)

If Kc1 = 5.9 × 10-2 and Kc2 = 6.4 × 10-5 at 25°C, what is the value of Kc for reaction (3)?

(3) H2C2O4(aq) + 2 H2O(l) ⇌ 2 H3O+(aq) + C2O42-(aq)

A) 3.8 × 10-6

B) 1.1 × 10-3

C) 5.9 × 10-2

D) 9.2 × 102

56) Acids donate protons to water according to the general equation:

HA(aq) + H2O(l) ⇌ H3O+(aq) + A–(aq)

Consider the following acids and their equilibrium constants for reaction with water at 25°C. If all the

acids have the same initial concentration, which is the strongest acid (i.e. which donates the most protons

to water)?

A) HBrO, Kc = 2.0 × 10-9

B) HNO2, Kc = 4.5 × 10-4

C) HF, Kc = 3.5 × 10-4

D) HIO3, Kc = 1.7 × 10-1

57) For acid solutions of the same molarity acid strength is proportional to the equilibrium concentration

of H3O+. For equimolar solutions of acids, which equilibrium expression below corresponds to the

strongest acid?

A) Kc = = 3.5 × 10-4

B) Kc = = 3.5 × 10-8

C) Kc = = 4.5 × 10-4

D) Kc = = 4.9 × 10–10

58) The equilibrium constant Kc for the reaction HF(aq) + H2O(l) ⇌ H3O+(aq) +F–(aq) is 3.5 × 10-4. What is

the equilibrium concentration of H3O+ if the initial concentration of HF is 1.0 M?

A) 1.0 M

B) 3.5 × 10-2 M

C) 1.9 × 10–2 M

D) 1.9 × 10-4 M

59) The solubility of 1:1 salts is measured by the equilibrium constant for the general reaction: MX(s) =

Mn+(aq) + Xn-(aq). Given the following salts and their equilibrium constants for the reaction above at

25°C, which salt is the least soluble?

A) MgCO3, Kc = 6.8 × 10-6

B) CaCO3, Kc = 5.0 × 10-9

C) SrCO3, Kc = 5.6 × 10–10

D) BaCO3, Kc = 2.6 × 10-9

60) Salt solubilities can be compared by the concentration of cation formed when the salt dissolves in the

general reaction: MaXb(s) ⇌ a Mb+(aq) + b Xa-(aq). Given the following salts and their equilibrium

constants for the reaction above at 25°C, which salt is the least soluble?

A) AgCl, Kc = 1.8 × 10–10

B) Ag2SO4, Kc = 1.2 × 10-5

C) CaCO3, Kc = 2.6 × 10-9

D) CaF2, Kc = 1.5 × 10–10

61) Consider the reaction

HCO3– (aq) + H2O (l) ⇌ CO3-2 (aq)+ H3O+ (aq)

The Keq for this reaction is 5.6 × 10–11. Describe what will happen to the reaction if the concentration of

each reactant is

[HCO3–] = 5.6 × 10–11 [H3O+] = 1.2 × 10–11 [CO3–] = 5.6 × 10–11

A) Reaction will shift right, concentration of products will increase.

B) Reaction will shift left, concentration of reactants will increase.

C) Reaction will not change, it is at equilibrium.

D) Not enough information to determine the answer.

62) Which of the following will result in an increase in the amount of NH4Cl?

NH4Cl (s) ⇌ NH3 (g) + HCl (g)

A) increasing the volume

B) decreasing the amount of HCl (g)

C) Iincreasing the amount of NH3 (g)

D) none of these

63) The pink and blue species below form a violet colored mixture at equilibrium:

[Co(H2O)6]2+ (aq) + 4 Cl– (aq) ⇌ [CoCl4]2- (aq) + 6 H2O (l)

(pink) (blue)

If the concentration of [Co(H2O)6]2+ is increased, what happens to the solution?

A) The concentration of [CoCl4]2- increases.

B) The concentration of [CoCl4]2- decreases.

C) The solution becomes colorless.

D) No color change is observed.

64) A crude type of disappearing ink is based on the following endothermic equilibrium:

[Co(H2O)6]Cl2 (aq) ⇌ [CoCl2(H2O)4] (aq) + 2 H2O (l)

(colorless) (blue)

If the reactant solution is used to write on a piece of paper and the paper is allowed to partially dry, what

can be done to bring out the colored handwriting?

A) add water

B) decrease the volume

C) put the paper in a freezer

D) put the paper in an oven

65) What effect will a change in temperature have on the value of Kp?

A) It will have no effect on the value of Kp.

B) The value of Kp always decreases with an increase in temperature.

C) The value of Kp always increases with an increase in temperature.

D) The value of Kp will decrease or increase with an increase in temperature, depending on whether the

reaction is exothermic or endothermic.

66) The dissolution of calcium hydroxide is exothermic:

Ca(OH)2(s) ⇌ Ca2+(aq) + 2 OH–(aq)

What happens when the solution of Ca(OH)2 is heated?

A) The amount of Ca(OH)2(s) decreases.

B) The amount of Ca(OH)2(s) increases.

C) The amount of Ca(OH)2(s) remains unchanged.

D) The Ca(OH)2(s) completely dissolves.

67) Calcium carbonate is relatively insoluble and the dissolution reaction is endothermic:

CaCO3(s) ⇌ Ca2+(aq) + CO32-(aq).

Which change in reaction condition below will shift the equilibrium to the right?

A) add an acid to react with CO32- ion

B) add an anion with which Ca2+ is even less soluble than calcium carbonate

C) increase the temperature

D) All of these will shift reaction to the right.

68) A catalyst increases the overall rate of reaction by lowering the activation energy, Ea, for

A) both the forward reaction and the reverse reaction.

B) neither the forward reaction nor the reverse reaction.

C) only the forward reaction.

D) only the reverse reaction.

69) A catalyst increases the rate of a chemical reaction by providing a lower-energy mechanism for the

reaction. When this occurs, which one of the following is not affected?

A) activation energy for the forward reaction

B) activation energy for the reverse reaction

C) equilibrium constant

D) rate of the reverse reaction

70) A reaction reaches dynamic equilibrium at a given temperature when

A) the amount of products exceeds the amount of reactants.

B) kfwd equals krev.

C) opposing reactions cease and the system is static.

D) the relative amounts of reactants and products are constant and ratefwd = raterev.

71) Find the equilibrium constant for the reaction: A(g) + B(g) ⇌ 2C(g) at 25°C when k equals 1.4 × 10–12

M-1s-1 for the reaction A(g) + B(g) → 2C(g) at 25°C and k equals 2.7 × 10–13 M-1s-1 for the reaction:

A) 3.8 × 10–25

B) 1.7 × 10–12

C) 1.1 × 10–12

D) 5.2

72) At 25°C, a certain first order reaction has a rate constant equal to 1.00 × 10-3 s-1 and an equilibrium

constant, Kc, equal to 4.18. What is the rate constant for the reverse reaction?

A) 2.39 × 10-4 s-1

B) 4.18 × 10-3 s-1

C) 2.39 × 102 s-1

D) 4.18 × 103 s-1

73) Nickel metal can be prepared by the reduction of nickel oxide:

NiO(s) + CO(g) ⇌ CO2(g) + Ni(s)

At 936 K, Kp = 4.54 × 103 and at 1125 K, Kp = 1.58 × 103. Which statement is true?

A) The activation energy decreases with increasing temperature.

B) The activation energy increases with increasing temperature.

C) The reaction is endothermic.

D) The reaction is exothermic.

74) The hexaammine cobalt(III) ion is very unstable in acidic aqueous solution:

[Co(NH3)6]3+(aq) + 6 H3O+(aq) → [Co(H2O)6]4+(aq) + 6 NH4+(aq)

However, solutions of hexaammine cobalt(III) can be stored in acidic solution for months without

noticeable decomposition. Which statement below about the equilibrium constant and the activation

energy for the reaction is true?

A) Keq < 103 and Ea is very small.

B) Keq > 103 and Ea is very small.

C) Keq < 103 and Ea is very large.

D) Keq > 103 and Ea is very large.

75) The reaction below virtually goes to completion because cyanide ion forms very stable complexes

with Ni2+ ion:

[Ni(H2O)6]2+(aq) + 4 CN–(aq) → [Ni(CN)4]2-(aq) + 6 H2O(l)

At the same time, incorporation of 14C labelled cyanide ion (14CN–) is very rapid:

[Ni(CN)4]2-(aq) + 4 14CN–(aq) = [Ni(14CN)4]2-(aq) + 4 CN–(aq)

Which statement below is correct with regard to stability and rate of reaction?

A) Equilibrium is static.

B) Stable species can react rapidly.

C) Stable species do not react rapidly.

D) Unstable species react rapidly.

Consider the interconversion of A molecules (shaded spheres) and B molecules (unshaded spheres)

according to the reaction A ⇌ B. Each of the following series of pictures represents a separate experiment

in which time increases from left to right.

76) Which of these experiments has resulted in an equilibrium state?

A) all of the experiments except experiment (1)

B) all of the experiments except experiment (2)

C) all of the experiments except experiment (3)

D) all of the experiments except experiment (4)

77) What is the value of the equilibrium constant Kc for the reaction A ⇌ B?

A) Kc = 0.33

B) Kc = 3.0

C) Kc = 12

D) Kc = 27

The following pictures represent the equilibrium state for four different reactions of the type

A atoms are unshaded. X atoms are shaded.

78) Which reaction has the largest equilibrium constant?

A) A2 + B2 ⇌ 2 AB

B) A2 + C2 ⇌ 2 AC

C) A2 + D2 ⇌ 2 AD

D) A2 + E2 ⇌ 2 AE

79) Which reaction has the smallest equilibrium constant?

A) A2 + B2 ⇌ 2 AB

B) A2 + C2 ⇌ 2 AC

C) A2 + D2 ⇌ 2 AD

D) A2 + E2 ⇌ 2 AE

80) The reaction A2 + B2 ⇌ 2 AB has an equilibrium constant Kc = 1.8. The following pictures represent

reaction mixtures that contain A2 molecules (shaded) and B2 molecules (unshaded), and AB molecules.

Which reaction mixture is at equilibrium?

A) reaction mixture (1)

B) reaction mixture (2)

C) reaction mixture (3)

D) reaction mixture (4)

81) The following pictures represent mixtures of cis–C2H2X2 molecules and trans-C2H2X2 molecules,

which interconvert according to the equation cis-C2H2X2 ⇌ trans-C2H2X2. If mixture (1) is at

equilibrium, which of the other mixtures are also at equilibrium?

A) mixture (2)

B) mixture (3)

C) mixture (4)

D) None of the other mixtures are at equilibrium.

82) The following pictures represent mixtures of cis–C2H2X2 molecules and trans-C2H2X2 molecules,

which interconvert according to the equation cis-C2H2X2 ⇌ trans-C2H2X2. If mixture (1) is at

equilibrium, which of the other mixtures are also at equilibrium?

A) mixture (2)

B) mixture (3)

C) mixture (4)

D) None of the other mixtures are at equilibrium.

83) The following pictures represent mixtures of A2B4 molecules and AB2 molecules, which interconvert

according to the equation A2B4 ⇌ 2 AB2. If mixture (1) is at equilibrium, which of the other mixtures are

also at equilibrium?

A) mixture (2)

B) mixture (3)

C) mixture (4)

D) None of the other mixtures are at equilibrium.

84) The following pictures represent mixtures of A2B4 molecules and AB2 molecules, which interconvert

according to the equation A2B4 ⇌ 2 AB2. If mixture (1) is at equilibrium, which of the other mixtures are

also at equilibrium?

A) mixture (2)

B) mixture (3)

C) mixture (4)

D) None of the other mixtures are at equilibrium.

85) Shown below is a concentration vs. time plot for the reaction A ⇌ B. For this reaction the value of the

equilibrium constant is

A) Kc < 1.

B) Kc = 0.

C) Kc = 1.

D) Kc > 1.

86) Shown below is a concentration vs. time plot for the reaction A ⇌ 2B. For this reaction the value of the

equilibrium constant is

A) Kc < 1.

B) Kc = 0.

C) Kc = 1.

D) Kc > 1.

87) Shown below is a concentration vs. time plot for the reaction A ⇌ B. For this reaction the value of the

equilibrium constant is

A) Kc < 1.

B) Kc = 0.

C) Kc = 1.

D) Kc > 1.

88) Shown below is a concentration vs. time plot for the reaction A ⇌ 2B. For this reaction the value of the

equilibrium constant is

A) Kc < 1.

B) Kc = 0.

C) Kc = 1.

D) Kc > 1.

89) Shown below is a concentration vs. time plot for the reaction A ⇌ B. For this reaction the value of the

equilibrium constant is

A) Kc < 1.

B) Kc = 0.

C) Kc = 1.

D) Kc > 1.

90) Shown below is a concentration vs. time plot for the reaction A ⇌ 2B. For this reaction the value of the

equilibrium constant is

A) Kc < 1.

B) Kc = 0.

C) Kc = 1.

D) Kc > 1.

91) The following picture represents the equilibrium state for the reaction A2 + B2 ⇌ 2AB. What is the

relationship between the rate constant for the forward reaction, kf, and the rate constant for the reverse

reaction kr?

A) kf < kr

B) kf = kr = 0

C) kf = kr

D) kf > kr

92) The following picture represents the equilibrium state for the reaction A2 + B2 ⇌ 2AB. What is the

relationship between the rate constant for the forward reaction, kf, and the rate constant for the reverse

reaction kr?

A) kf < kr

B) kf = kr = 0

C) kf = kr

D) kf > kr

93) The following picture represents the equilibrium state for the reaction A2 + B2 ⇌ 2AB. What is the

relationship between the rate constant for the forward reaction, kf, and the rate constant for the reverse

reaction kr?

A) kf < kr

B) kf = kr = 0

C) kf = kr

D) kf > kr

The reaction A2 + B2 ⇌ 2AB has an equilibrium constant Kc = 1.8. The following pictures represent

reaction mixtures that contain A2 molecules (shaded) and B2 molecules (unshaded), and AB molecules.

94) Which nonequilibrium mixture will react in the forward direction to reach equilibrium?

A) reaction mixture (1)

B) reaction mixture (2)

C) reaction mixture (3)

D) reaction mixture (4)

95) Which nonequilibrium mixtures will react in the reverse direction to reach equilibrium?

A) reaction mixtures (1) and (2)

B) reaction mixtures (1) and (4)

C) reaction mixtures (2) and (3)

D) reaction mixtures (3) and (4)