Deck 13: Chemical Equilibrium

Question 1

A mixture of carbon monoxide,hydrogen,and methanol is at equilibrium.The balanced chemical equation is: CO(g)+ 2H₂(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

Answer 1

42.8

Question 2

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

Answer 2

4)8 × 10⁹ M

Question 3

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

Answer 3

54.1

Question 4

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 5

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 6

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 7

Nitric oxide reacts with oxygen to form nitrogen dioxide:
2 NO(g)+ O₂(g)⇌ 2 NO₂(g)
What is K_c for the forward reaction if the equilibrium concentration of NO is 0.200 M,O₂ is 0.100 M,and NO₂ is 0.250 M at 25°C?

A)8)00 × 10^-2
B)6)41 × 10^-2
C)12.5
D)15.6

Question 8

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: 1/2 H₂(g)+ 1/2 Br₂(g)== HBr(g)?

A)3)52 × 10^-2
B)0)265
C)3)77
D)28.4

Question 9

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

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

Question 10

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

A)K_c´ =
B)K_c´ =
C)K_c´ =
D)K_c´ =

Question 11

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

Question 12

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 13

The equilibrium equation is also known as the law of

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

Question 14

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^' =

Question 15

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.

Question 16

If K_c equals 0.11 at 25°C for the reaction: N₂O₄(g)⇌ 2 NO₂(g),what is K_c for the reaction: NO₂(g)⇌ 1/2 N₂O₄(g)?

A)0)33
B)3)0
C)4)5
D)9)1

Question 17

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)K_p =
D)K_p =

Question 18

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 19

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 20

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 21

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 22

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 23

If K_c = 2.0 x 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 24

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 25

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 26

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 27

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 28

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 29

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 30

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 31

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 32

If K_c = 0.900,and K_p = 538 for a hypothetical reaction,which of the equations below could represent the reaction at 25°C?

A)A(g)+ B(s)⇌ 3 C(g)
B)A(l)+ 2 B(g)⇌ 2 C(g)
C)B(g)⇌ C(l)+ D(l)
D)A(g)⇌ 2 C(s)+ D(g)

Question 33

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 34

For which one of the following reactions will K_c = K_p?

A)CO(g)+ 2 H₂(g)⇌ CH₃OH(g)
B)ZnO(s)+ CO(g)⇌ Zn(s)+ CO₂(g)
C)2 O₃(g)⇌ 3 O₂(g)
D)COCl₂(g)⇌ CO(g)+ Cl₂(g)

Question 35

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 36

The decomposition of ammonia is: 2 NH₃(g)⇌ N₂(g)+ 3 H₂(g).If the partial pressure of ammonia is 1.6 × 10^-3 atm and the partial pressures of N₂ and H₂ are each 0.25 atm at equilibrium,what is the value for K_c at 400°C for the forward reaction?

A)0)50
B)1)4
C)1)5 × 10³
D)4)6 × 10⁶

Question 37

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 38

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 39

Which equilibrium below is homogeneous?

A)BaSO₄(s)⇌ Ba²⁺(aq)+ SO₄^2-(aq)
B)2 H₂O₂(l)⇌ 2 H₂O(l)+ O₂(g)
C)NH₄NO₃(s)⇌ N₂O(g)+ 2 H₂O(g)
D)2 CO(g)+ O₂(g)⇌ 2 CO₂(g)

Question 40

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 41

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 42

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 43

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 44

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 45

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 46

For the reaction: 4 HCl(g)+ O₂(g)⇌ 2 Cl₂(g)+ 2 H₂O(l),the equilibrium constant is 0.063 at 400 K.If the reaction quotient is 0.100,which of the following statements is not correct?

A)[HCl] will increase.
B)[O₂] will increase.
C)[Cl₂] will decrease.
D)[H₂O] will increase.

Question 47

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 48

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 49

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 50

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 51

For the reaction,A(g)+ 2 B(g)⇌ 2 C(g),K_c = 1 × 10^-10 at 25°C.Which of the following statements is true?

A)Δn = +1
B)The concentration of the products is greater than the concentration of the reactants.
C)The reaction is favored in the reverse direction.
D)The value of K_p will be larger than the value for K_c.

Question 52

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 53

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 54

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 55

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 56

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 57

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 58

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 59

Which statement is true for a reaction with K_c equal to 2.43 × 10^-12?

A)Increasing the temperature will not change the value of K_c.
B)There are appreciable concentrations of both reactants and products.
C)The reaction proceeds hardly at all towards completion.
D)The reaction proceeds nearly all the way to completion.

Question 60

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 61

Gaseous hydrogen bromide decomposes at elevated temperatures according to the following equation:
2 HBr(g)⇌ H₂(g)+ Br₂(g).
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 62

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 63

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product?
C(s)+ 2 H₂(g)⇌ CH₄(g)ΔH° = -74.8 kJ

A)adding more C
B)decreasing the concentration of H₂
C)increasing the concentration of H₂
D)increasing the concentration of CH₄

Question 64

The enthalpy for the following reaction is 136 kJ.If the reaction takes place in a closed container,which one of the following reaction conditions will not decrease the concentration of water vapor?
2 NaHCO₃(s)⇌ Na₂CO₃(s)+ CO₂(g)+ H₂O(g)

A)add CO₂
B)cool the container
C)decrease the volume of the container
D)remove some NaHCO₃

Question 65

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 66

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 67

Ammonium bromide is a crystalline solid that decomposes endothermically when heated:
NH₄Br(s)⇌ NH₃(g)+ HBr(g).When solid NH₄Br is added to an evacuated flask at 300°C,which change in reaction conditions below will cause the equilibrium to shift to the right?

A)add more NH₃
B)add more NH₄Br
C)decrease the temperature
D)double the volume of the container

Question 68

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 69

For a homogeneous equilibrium of gases,which of the following changes in reaction conditions will not alter the equilibrium concentrations?

A)addition of an inert gas to the reaction mixture
B)addition of reactants or products
C)decreasing the pressure or volume
D)increasing the temperature

Question 70

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 71

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 72

Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide:
FeO(s)+ CO(g)⇌ Fe(s)+ CO₂(g)
Which of the following changes in condition will cause the equilibrium to shift to the right?

A)add FeO
B)add CO
C)add CO₂
D)raise the temperature

Question 73

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product?
C(s)+ 2 H₂(g)⇌ CH₄(g)ΔH° = - 74.8 kJ

A)adding He
B)adding more C
C)decreasing the volume
D)increasing the volume

Question 74

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 75

"If a stress is applied to a reaction mixture at equilibrium,the reaction occurs in the direction that will relieve the stress." This statement is called

A)the First Law of Thermodynamics.
B)the Law of Combining Volumes.
C)the Law of Mass Action.
D)Le Châtelier's principle.

Question 76

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 77

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 78

Which of the following changes in reaction conditions will alter the composition of an equilibrium mixture of gases for a reaction having unequal moles of gaseous products and gaseous reactants?

A)addition of reactants or products
B)decreasing the pressure or volume
C)increasing the temperature
D)All of these will alter the equilibrium concentrations.

Question 79

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product?
C(s)+ 2 H₂(g)⇌ CH₄(g)ΔH° = -74.8 kJ

A)adding more C
B)increasing the volume
C)lowering the temperature
D)raising the temperature

Question 80

Which change in the system will drive equilibrium to the left in the reaction below?
N₂O₅(g)⇌ NO₂(g)+ NO₃(g)

A)decrease the amount of NO₃
B)increase the amount of N₂O₅
C)increase the pressure
D)increase the volume