Deck 14: Chemical Equilibrium

Question 1

If K_c is the equilibrium constant for a forward reaction what is K_c' for the reverse reaction?

A)- K_c
B)K_c
C)(K_c)^-1
D)none of these

Answer 1

(K_c)^-1

Question 2

Write the equilibrium equation for the reverse reaction: 2 CH₄(g)+ 3 O₂(g)⇌ 2 CO(g)+ 4 H₂O(g)

A)K_p^' =
B)K_p^' =
C)K_p^' =
D)K_p^' =

Answer 2

K_p^' =

Question 3

Which of the following statements is false regarding the equilibrium constant,K_c?

A)K_c for a reaction at a particular temperature always has the same value.
B)K_c for the reverse reaction is the negative of K_c for the forward reaction.
C)The numerical value of K_c depends on the form of the balanced equation.
D)When quoting K_c it is customary to omit units.

Answer 3

K_c for the reverse reaction is the negative of K_c for the forward reaction.

Question 4

A mixture of carbon monoxide,hydrogen,and methanol is at equilibrium.The balanced chemical equation is: CO(g)+ 2 H₂(g)⇌ CH₃OH(g).At 250°C,the mixture contains 0.0960 M CO,0.191 M H₂,and 0.150 M CH₃OH.What is the value for K_c?

A)2.33 × 10^-2
B)0.244
C)4.09
D)42.8

Question 5

What is true about the relationship of K_p and K_c for the reaction: 2 CH₄(g)+ 3 O₂(g)⇌ 2 CO(g)+ 4 H₂O(g)?

A)K_p < K_c
B)K_p = K_c
C)K_p > K_c
D)K_p and K_c are not related.

Question 6

Which statement about the equilibrium constant is true? The value of K_c

A)changes as product concentration changes.
B)changes as reactant concentration changes.
C)changes as temperature changes.
D)never changes.

Question 7

If K_c is the equilibrium constant for a forward reaction,2 A⇌ B,what is K_c' for the reaction 4 A⇌ 2B?

A)
K_c
B)K_c
C)2 K_c
D)(K_c)²

Question 8

The oxidation of sulfur dioxide by oxygen to sulfur trioxide has been implicated as an important step in the formation of acid rain: 2 SO₂(g)+ O₂(g)⇌ 2 SO₃(g).If the equilibrium partial pressures of SO₂,O₂,and SO₃ are 0.564 atm,0.102 atm,and 0.333 atm respectively at 1000 K,what is K_p at that temperature?

A)0.292
B)3.42
C)5.79
D)8.11

Question 9

Which one of the following statements does not describe the equilibrium state?

A)Equilibrium is dynamic and there is no net conversion to reactants and products.
B)The concentration of the reactants is equal to the concentration of the products.
C)The concentration of the reactants and products reach a constant level.
D)The rate of the forward reaction is equal to the rate of the reverse reaction.

Question 10

K_p = 1.5 × 10³ at 400°C for the reaction 2 NH₃(g)⇌ N₂(g)+ 3 H₂(g).What is the value of K_p for the reaction: 2 N₂(g)+ 6 H₂(g)⇌ 4 NH₃(g)?

A)4.4 × 10^-7
B)3.3 × 10^-4
C)6.7 × 10^-4
D)2.3 × 10⁶

Question 11

The equilibrium equation is also known as the law of

A)coefficients.
B)constant concentration.
C)dynamic equilibrium.
D)mass action.

Question 12

Which statement about the equilibrium constant is true? The value of K_c

A)changes as product concentration changes.
B)changes as reactant concentration changes.
C)changes as temperature changes.
D)changes under the conditions described in A-C.

Question 13

Write the equilibrium equation for the forward reaction: 2 CH₄(g)+ 3 O₂(g)⇌ 2 CO(g)+ 4 H₂O(g)

A)K_p =
B)K_p=
C)Kp =
D)K_p =

Question 14

What is the equilibrium equation for the reaction: NH₄NO₃(s)⇌ N₂O(g)+ 2 H₂O(g)?

A)K_p = [N₂O]
B)K_p = [N₂O][H₂O]
C)K_p = [N₂O][H₂O]²
D)K_p =

Question 15

If K_c = 7.04 × 10^-2 for the reaction: 2 HBr(g)⇌ H₂(g)+ Br₂(g),what is the value of K_c for the reaction: ?

A)3.52 × 10^-2
B)0.265
C)3.77
D)28.4

Question 16

For the reaction: N₂(g)+ 2 O₂(g)⇌ 2 NO₂(g),K_c = 8.3 × 10^-10 at 25°C.What is the concentration of N₂ gas at equilibrium when the concentration of NO₂ is twice the concentration of O₂ gas?

A)2.1 × 10^-10 M
B)4.2 × 10^-10 M
C)2.4 × 10⁹ M
D)4.8 × 10⁹ M

Question 17

Given the reaction: 2 HI ⇌ H₂ + I₂.If K_c^' for the reverse reaction is 1.85 × 10^-2 at 425°C,what is K_c for the forward reaction at the same temperature?

A)-1.85 × 10^-2
B)1.85 × 10^-2
C)3.70 × 10^-2
D)54.1

Question 18

Which one of the following statements about the equilibrium constant,K_p,is false?

A)Δn is equal to the sum of the coefficients of the gaseous products minus the sum of the coefficients of the gaseous reactants.
B)The relationship between K_p and K_c is: K_p = K_c (RT)^Δn
C)The units for K_p are usually omitted.
D)Total pressures are used in the equilibrium equation in place of molar concentrations.

Question 19

Nitric oxide reacts with oxygen to form nitrogen dioxide: 2 NO(g)+ O₂(g)⇌ 2 NO₂(g)
What is K_c' for the reverse reaction if the equilibrium concentration of NO is 0.300 M,O₂ is 0.200 M,and NO₂ is 0.530 M at 25°C?

A)0.0340
B)0.0641
C)0.624
D)15.6

Question 20

K_p is related to K_c by the equation K_p = K_c (RT)ⁿ.What is the value of n for the reaction below? NH₄NO₃(s)⇌ N₂O(g)+ 2 H₂O(g)

A)-2
B)-1
C)+1
D)+2

Question 21

Phosphorus pentachloride decomposes to phosphorus trichloride and chlorine gas at elevated temperatures by the following reaction: PCl₅(g)⇌ PCl₃(g)+ Cl₂(g).If K_c = 1.8 at 250°C.
What is the value of K_p at the same temperature?

A)4.2 × 10^-2
B)8.8 × 10^-2
C)65
D)77

Question 22

The decomposition of ammonia is: 2 NH₃(g)= N₂(g)+ 3 H₂(g).If K_p is 1.5 × 10³ at 400°C,what is the partial pressure of ammonia at equilibrium when N₂ is 0.10 atm and H₂ is 0.15 atm?

A)2.2 × 10^-7 atm
B)4.7 × 10^-4 atm
C)2.1 × 10³ atm
D)4.4 × 10⁶ atm

Question 23

What is the equilibrium equation for the dissociation of formic acid in water? HCOOH (aq)+ H₂O (l)⇌ H₃O⁺ (aq)+ HCOO^- (aq)

A)K_c =
B)K_c =
C)K_c =
D)K_c =

Question 24

The equilibrium constant,K_p,equals 3.40 at 25°C for the isomerization reaction: cis-2-butene ⇌ trans-2-butene.
If a flask initially contains 1.00 atm of each gas,in what direction will the system shift to reach equilibrium?

A)It will shift left.
B)It will shift right.
C)The system is already at equilibrium.
D)The system is not at equilibrium and will remain in an unequilibrated state.

Question 25

Given the hypothetical reaction: 2 A(s)+ x B(g)⇌ 3 C(g),K_p = 0.0105 and K_c = 0.45 at 250°C.What is the value of the coefficient x?

A)1
B)2
C)3
D)4

Question 26

What is the value for K_c for the following reaction: PbCl₂(s)⇌ Pb²⁺(aq)+ 2 Cl^-(aq),
If PbCl₂(s)= 1.50 grams,[Pb²⁺] = 1.6 × 10^-2 M and [Cl^-] = 3.2 × 10^-2 M at equilibrium? (The molar mass of PbCl₂(s)is 278 g/mol and its density is 5.85 g/cm³. )

A)7.6 × 10^-7
B)1.6 × 10^-5
C)6.2 × 10⁴
D)1.3 × 10⁶

Question 27

What is the equilibrium equation for the following reaction? C₂H₄ (g)+ 3 O₂ (g)⇌ 2 CO₂ (g)+ 2 H₂O (l)

A)K_p =
B)K_p =
C)K_p =
D)K_p =

Question 28

As a rule,which of the following phases are not included in the equilibrium constant expression? I.pure liquids II.pure solids III.aqueous solutions IV.gases

A)I,II
B)I,IV
C)III,IV
D)II,III

Question 29

A 1.50 L vessel contains an equilibrium mixture of 0.100 mol of NO,0.150 mol of Br₂,and 0.250 mol of NOBr at 25°C.What is the value of K_p for the reaction below? 2 NO(g)+ Br₂(g)⇌ 2 NOBr(g)

A)2.56
B)62.5
C)1.28 × 10²
D)1.53 × 10³

Question 30

At a certain temperature,bromine and nitric oxide react to form nitrosyl bromide: Br₂(g)+ 2 NO(g)⇌ 2 NOBr(g).
When 0.010 mol Br₂ is mixed with 0.025 mol NO and 0.015 mol NOBr in a 2.50 L flask,the concentration of NOBr decreases.Which statement below is true?

A)K_c < 36
B)K_c > 36
C)K_c < 90
D)K_c > 90

Question 31

Which of the following is the correct equilibrium constant expression for this reaction? (Hint: check the reaction coefficients) Fe(s)+ O₂(g)⇌ Fe₂O₃(s)

A)K =
B)K =
C)K =
D)K =
E)K = [O₂}³

Question 32

What is the equilibrium constant,K_c,for the reaction: 2 Hg(l)+ O₂(g)⇌ 2 HgO(s)
If the amounts of reactants and products at equilibrium are: 1.00 g of HgO(s),2.00 mL of Hg(l),and 1.60 M O₂(g)? (The molar mass and density of HgO(s)is 217 g/mol,and 1.10 g/cm³.The molar mass and density of Hg(l)is 201 g/mol,and 13.6 g/mL. )

A)6.85 × 10^-4
B)4.66 × 10^-2
C)0.625
D)1.46 × 10³

Question 33

The equilibrium constant is equal to 5.00 at 1300 K for the reaction: 2 SO₂(g)+ O₂(g)⇌ 2 SO₃(g).
If initial concentrations are [SO₂] = 1.20 M,[O₂] = 0.45 M,and [SO₃] = 1.80 M,the system is

A)at equilibrium.
B)not at equilibrium and will remain in an unequilibrated state.
C)not at equilibrium and will shift to the left to achieve an equilibrium state.
D)not at equilibrium and will shift to the right to achieve an equilibrium state.

Question 34

At a certain temperature,bromine and nitric oxide react to form nitrosyl bromide: Br₂(g)+ 2 NO(g)⇌ 2 NOBr(g).
When initial amounts of Br₂,NO,and NOBr are mixed,the concentration of NOBr increases.Which statement below is true?

A)K_c < Q
B)K_c > Q
C)K_c = Q
D)More information is needed to make a statement about K_c.

Question 35

What is the equilibrium equation for the following reaction? FeS(s)+ 2 H₃O⁺ (aq)⇌ Fe²⁺(aq)+ H₂S (aq)+ 2 H₂O (l)

A)K_c =
B)K_c =
C)K_c =
D)K_c =

Question 36

Cyclohexane (C₆H₁₂)undergoes a molecular rearrangement in the presence of AlCl₃ to form methylcyclopentane (MCP)according to the equation: C₆H₁₂ ⇌ MCP
If K_c = 0.143 at 25°C for this reaction,predict the direction the reaction will shift if the initial concentrations of C₆H₁₂ and MCP are 0.200 M and 0.100 M,respectively.The system

A)will shift left.
B)will shift right.
C)is already at equilibrium.
D)is not at equilibrium and will remain in an unequilibrated state.

Question 37

Given the reaction at a certain temperature: 2 HI(g)⇌ H₂(g)+ I₂(g).At equilibrium,the partial pressure of HI is 1.8 × 10^-3 atm,and the partial pressures for H₂ and I₂ are 0.10 atm each.Find K_p at that temperature.

A)3.2 × 10^-4
B)5.6 × 10¹
C)3.1 × 10³
D)3.1 × 10⁴

Question 38

If K_c = 2.0 × 10³³ at 25°C,for the following reaction: H₂(g)+ Cl₂(g)⇌ 2 HCl(g),then find K_p at the same temperature.

A)8.2 × 10³¹
B)9.7× 10³²
C)2.0 × 10³³
D)4.9 × 10³⁴

Question 39

What is the equilibrium equation for the following reaction? 2 H₂O (l)⇌ H₃O⁺ (aq)+ OH^- (aq)

A)K_c =
B)K_c =
C)K_c =
D)K_c = [H₃O⁺] [OH^-]

Question 40

The decomposition of ammonia is: 2 NH₃(g)⇌ N₂(g)+ 3 H₂(g).If the pressure of ammonia is 1.0 × 10^-3 atm,and the pressures of N₂ and H₂ are each 0.20 atm,what is the value for K_p' at 400°C for the reverse reaction?

A)-6.2 × 10^-4
B)-1.6 × 10³
C)6.2 × 10^-4
D)1.6 × 10³

Question 41

When baking soda is heated it decomposes according to the following reaction: 2 NaHCO₃(s)⇌ Na₂CO₃(s)+ H₂O(g)+ CO₂(g)
If sufficient baking soda is placed in a container and heated to 90°C,the total pressure of the gases is 0.5451 atm.What is the value of K_p at that temperature?

A)0.07428
B)0.2973
C)0.4228
D)1.091

Question 42

At a certain temperature the equilibrium constant,K_c,equals 0.11 for the reaction: 2 ICl(g)⇌ I₂(g)+ Cl₂(g).
What is the equilibrium concentration of ICl if 0.75 mol of I₂ and 0.75 mol of Cl₂ are initially mixed in a 2.0-L flask?

A)0.23 M
B)0.28 M
C)0.45 M
D)0.56

Question 43

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)K_c =
= 3.5 × 10^-4
B)K_c =
= 3.5 × 10^-8
C)K_c =
= 4.5 × 10^-4
D)K_c =
= 4.9 × 10^-10

Question 44

Cyclohexane (C₆H₁₂)undergoes a molecular rearrangement in the presence of AlCl₃ to form methylcyclopentane (CH₃C₅H₉)according to the equation: C₆H₁₂ ⇌ CH₃C₅H₉
If K_c = 0.143 at 25°C for this reaction,find the equilibrium concentrations of C₆H₁₂ and CH₃C₅H₉ if the initial concentrations are 0.200 M and 0.100 M,respectively.

A)[C₆H₁₂] = 0.0625 and [CH₃C₅H₉] = 0.062 M
B)[C₆H₁₂] = 0.138 and [CH₃C₅H₉] = 0.162 M
C)[C₆H₁₂] = 0.262 M and [CH₃C₅H₉] = 0.038 M
D)[C₆H₁₂] = 0.282 and [CH₃C₅H₉] = 0.018 M

Question 45

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)+ C₂O₄^2-(aq)
If K_c1 = 5.9 × 10^-2 and K_c2 = 6.4 × 10^-5 at 25°C,what is the value of K_c for reaction (3)?
(3)H₂C₂O₄(aq)+ 2 H₂O(l)⇌ 2 H₃O⁺(aq)+ C₂O₄^2-(aq)

A)3.8 × 10^-6
B)1.1 × 10^-3
C)5.9 × 10^-2
D)9.2 × 10²

Question 46

Ammonium carbamate can dissociate into gases at 25°C according to the reaction: NH₂COONH₄(s)⇌ 2 NH₃(g)+ CO₂(g)
If sufficient ammonium carbamate is sealed in a flask,the total pressure will be 0.117 atm at equilibrium.What is the value of K_p at 25°C?

A)2.37 × 10^-4
B)2.00 × 10^-4
C)1.60 × 10^-3
D)3.42 × 10^-1

Question 47

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 K_c 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

Question 48

Salt solubilities can be compared by the concentration of cation formed when the salt dissolves in the general reaction: M_aX_b(s)⇌ a M^b+(aq)+ b X^a-(aq).Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

A)AgCl,K_c = 1.8 × 10^-10
B)Ag₂SO₄,K_c = 1.2 × 10^-5
C)CaCO₃,K_c = 2.6 × 10^-9
D)CaF₂,K_c = 1.5 × 10^-10

Question 49

Phosphorus pentachloride decomposes to phosphorus trichloride at high temperatures according to the reaction: PCl₅(g)⇌ PCl₃(g)+ Cl₂(g)
At 250°C,0.250 M PCl₅ is added to a flask.If K_c = 1.80,what are the equilibrium concentrations of each gas?

A)[PCl₅] = 0.0280 M,[PCl₃] = 0.222 M,[Cl₂] = 0.222 M
B)[PCl₅] = 1.25 M,[PCl₃] = 0.474 M,[Cl₂] = 0.474 M
C)[PCl₅] = 1.80 M,[PCl₃] = 1.80 M,[Cl₂] = 1.80 M
D)[PCl₅] = 2.27 M,[PCl₃] = 2.02 M,[Cl₂] = 2.02 M

Question 50

The equilibrium constant K_c 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

Question 51

Consider the reaction HCO₃^- (aq)+ H₂O (l)⇌ CO₃^-2 (aq)+ H₃O+ (aq)
The K_eq 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.

Question 52

An equilibrium mixture of CO,O₂ and CO₂ at a certain temperature contains 0.0010 M CO₂ and 0.0015 M O₂.At this temperature,K_c,equals 1.4 × 10² for the reaction: 2 CO(g)+ O₂(g)⇌ 2 CO₂(g).
What is the equilibrium concentration of CO?

A)4.8 × 10^-6 M
B)2.2 × 10^-3 M
C)9.3 × 10^-2 M
D)3.1 × 10^-1 M

Question 53

K_p is equal to 48.70 at 731 K for the reaction: H₂(g)+ I₂(g)⇌ 2 HI(g).Initially the mixture contains 0.08592 atm each of H₂ and I₂ and 1.0000 atm of HI.What is the pressure of HI at equilibrium?

A)0.7955 atm
B)0.9108 atm
C)0.9140 atm
D)0.9498 atm

Question 54

At a certain temperature,K_c equals 1.4 × 10² for the reaction: 2 CO(g)+ O₂(g)⇌ 2 CO₂(g).
If a 2.50-L flask contains 0.400 mol of CO₂ and 0.100 mol of O₂ at equilibrium,how many moles of CO are also present in the flask?

A)0.422 mol
B)0.169 mol
C)0.107 mol
D)0.0114 mol

Question 55

The solubility of 1:1 salts is measured by the equilibrium constant for the general reaction: MX(s)= Mⁿ⁺(aq)+ X^n-(aq).Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

A)MgCO₃,K_c = 6.8 × 10^-6
B)CaCO₃,K_c = 5.0 × 10^-9
C)SrCO₃,K_c = 5.6 × 10^-10
D)BaCO₃,K_c = 2.6 × 10^-9

Question 56

The equilibrium constant,K_p,equals 3.40 for the isomerization reaction: cis-2-butene ⇌ trans-2-butene.
If a flask initially contains 0.250 atm of cis-2-butene and 0.125 atm of trans-2-butene,what is the equilibrium pressure of each gas?

A)P(cis-2-butene)= 0.037 atm,P(trans-2-butene)= 0.125 atm
B)P(cis-2-butene)= 0.048 atm,P(trans-2-butene)= 0.165 atm
C)P(cis-2-butene)= 0.074 atm,P(trans-2-butene)= 0.250 atm
D)P(cis-2-butene)= 0.085 atm,P(trans-2-butene)= 0.290 atm

Question 57

The esterification of acetic acid and ethanol is given by the reaction below: C₂H₅OH(aq)+ CH₃COOH(aq)⇌ CH₃COOC₂H₅(aq)+ H₂O(l)
When 1.00 mol of ethanol was mixed with 2.00 mol of acid in a 1.00 L flask,0.86 mol of ester was formed at room temperature.What is the value of the equilibrium constant,K_c?

A)0.43
B)2.3
C)4.6
D)5.4

Question 58

The following two isomers of C₃H₇NO exist in equilibrium with each other in solution: If K_c = 0.57 at 25°C and the initial concentration of the reactant is 0.50 M and the product is 0.70 M,what are the concentrations at equilibrium?

A)[reactant] = 0.43 M and [product] = 0.24 M
B)[reactant] = 0.67 M and [product] = 0.38 M
C)[reactant] = 0.76 M and [product] = 0.44 M
D)[reactant] = 0.82 M and [product] = 0.47 M

Question 59

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,K_c = 2.0 × 10^-9
B)HNO₂,K_c = 4.5 × 10^-4
C)HF,K_c = 3.5 × 10^-4
D)HIO₃,K_c = 1.7 × 10^-1

Question 60

For the isomerization reaction: butane ⇌ isobutane
K_p equals 25 at 500°C.If the initial pressures of butane and isobutane are 10.atm and 0.0 atm,respectively,what are the pressures of the two gases at equilibrium?

A)P(butane)= 0.38 atm and P(isobutane)= 9.6 atm
B)P(butane)= 0.40 atm and P(isobutane)= 10.atm
C)P(butane)= 9.6 atm and P(isobutane)= 0.38 atm
D)P(butane)= 10 atm and P(isobutane)= 0.40 atm

Question 61

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.

Question 62

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

Question 63

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.
What is the value of the equilibrium constant K_c for the reaction A ⇌ B?

A)K_c = 0.33
B)K_c = 3.0
C)K_c = 12
D)K_c = 27

Question 64

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

Question 65

What effect will a change in temperature have on the value of K_p?

A)It will have no effect on the value of K_p.
B)The value of K_p always decreases with an increase in temperature.
C)The value of K_p always increases with an increase in temperature.
D)The value of K_p will decrease or increase with an increase in temperature,depending on whether the reaction is exothermic or endothermic.

Question 66

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.

Question 67

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.

Question 68

Calcium carbonate is relatively insoluble and the dissolution reaction is endothermic: CaCO₃(s)⇌ Ca²⁺(aq)+ CO₃^2-(aq).
Which change in reaction condition below will shift the equilibrium to the right?

A)add an acid to react with CO₃^2- 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.

Question 69

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

Question 70

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

Question 71

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)K_eq < 10³ and E_a is very small.
B)K_eq > 10³ and E_a is very small.
C)K_eq < 10³ and E_a is very large.
D)K_eq > 10³ and E_a is very large.

Question 72

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.
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)

Question 73

A reaction reaches dynamic equilibrium at a given temperature when

A)the amount of products exceeds the amount of reactants.
B)k_fwd equals k_rev.
C)opposing reactions cease and the system is static.
D)the relative amounts of reactants and products are constant and rate_fwd = rate_rev.

Question 74

The reaction A₂ + B₂ ⇌ 2 AB has an equilibrium constant K_c = 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)

Question 75

The following pictures represent the equilibrium state for four different reactions of the type A atoms are unshaded.X atoms are shaded.
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

Question 76

Nickel metal can be prepared by the reduction of nickel oxide: NiO(s)+ CO(g)⇌ CO₂(g)+ Ni(s)
At 936 K,K_p = 4.54 × 10³ and at 1125 K,K_p = 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.

Question 77

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.

Question 78

A catalyst increases the overall rate of reaction by lowering the activation energy,E_a,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.

Question 79

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

Question 80

The following pictures represent the equilibrium state for four different reactions of the type A atoms are unshaded.X atoms are shaded.
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