Deck 16: Principles of Chemical Reactivity: Equilibria

Question 1

Given the following chemical equilibrium
COCl₂(g) $\rightleftharpoons$ CO(g) + Cl₂(g), calculate the value of K_c when K_p = 6.5 × 10¹¹ at 298 K. (R = 0.08206 L?atm/mol ? K)

A) 1.5 × 10^-12
B) 3.8 × 10^-11
C) 1.1 × 10⁹
D) 2.7 × 10¹⁰
E) 1.6 × 10¹³

Answer 1

2.7 × 10¹⁰

Question 2

Which of the following is the correct balanced equation for the equilibrium expression given below?
$K _ { p } = \frac { P _ { \mathrm { SO } _ { 3 } } ^ { 2 } } { P _ { \mathrm { O } _ { 2 } } P _ { \mathrm { SO } _ { 2 } } ^ { 2 } }$

A) 2 SO₂(g) + O₂(g) $\rightleftharpoons$ 2 SO₃(g)
B) 2 SO₃(g) $\rightleftharpoons$ 2 SO₂(g) + O₂(g)
C) 2 SO₃(aq) $\rightleftharpoons$ 2 SO₂(aq) + O₂(aq)
D) 2 SO₂(aq) + O₂(aq) $\rightleftharpoons$ 2 SO₃(aq)
E) SO₂(g) + $\frac { 1 } { 2 }$ O₂(g) $\rightleftharpoons$ SO₃(g)

Answer 2

2 SO₂(g) + O₂(g) $\rightleftharpoons$ 2 SO₃(g)

Question 3

Which of the following is always true for a reaction where
K_c is $4.97 \times 10^{ - 8}$ at 25°C?

A) The reaction mixture contains mostly reactants at equilibrium.
B) The reaction mixture contains mostly products at equilibrium.
C) The rate of reaction is very slow.
D) There are approximately equal moles of reactants and products at equilibrium.
E) Both A and C.

Answer 3

The reaction mixture contains mostly reactants at equilibrium.

Question 4

Which of the following expressions for K is correct for the reaction given below?
HF(aq) + H₂O( $\ell$ ) $\rightleftharpoons$ F^-(aq) + H₃O⁺(aq)

A) $K = \frac { [ \mathrm { HF } ] } { \left[ \mathrm { F } ^ { - } \right] }$
B) $K = \left[ \mathrm { H } _ { 3 } \mathrm { O } ^ { + } \right]$
C) $K = \frac { \left[ \mathrm { F } ^ { - } \right] \left[ \mathrm { H } _ { 3 } \mathrm { O } ^ { + } \right] } { [ \mathrm { HF } ] }$
D) $K = \frac { \left[ \mathrm { F } ^ { - } \right] } { [ \mathrm { HF } ] }$
E) $K = \frac { [ \mathrm { HF } ] } { \left[ \mathrm { F } ^ { - } \right] \left[ \mathrm { H } _ { 3 } \mathrm { O } ^ { + } \right] }$

Question 5

Write the expression for K_p for the reaction below.
2 NOBr(g) $\rightleftharpoons$ 2 NO(g) + Br₂( $\ell$ )

A) $K _ { p } = \frac { P _ { \mathrm { NOBr } } ^ { 2 } P _ { \mathrm { Br } _ { 2 } } } { P _ { \mathrm { NO } } ^ { 2 } }$
B) $K _ { \mathrm { p } } = \frac { P _ { \mathrm { NO } } ^ { 2 } } { P _ { \mathrm { NOBr } } ^ { 2 } }$
C) $K _ { \mathrm { p } } = \frac { P _ { \mathrm { NOBr } } } { P _ { \mathrm { NO } } }$
D) $K _ { \mathrm { p } } = \frac { P _ { \mathrm { NO } } ^ { 2 } } { p _ { \mathrm { NOBr } } ^ { 2 } P _ { \mathrm { Br } _ { 2 } } }$
E) $K _ { p } = \left[ \mathrm { Br } _ { 2 } \right]$

Question 6

For which of the following reactions is K_c = K_p?

A) N₂(g) + 3 H₂(g) $\rightleftharpoons$ 2 NH₃(g)
B) CO(g) + H₂O(g) $\rightleftharpoons$ CO₂(g) + H₂(g)
C) CO(g) + 3 H₂(g) $\rightleftharpoons$ CH₄(g) + H₂O(g)
D) CaO(s) + CO₂(g) $\rightleftharpoons$ CaCO₃(s)
E) HBr(g) $\rightleftharpoons$ ½ H₂(g) + ½ Br₂( $\ell$ )

Question 7

The reaction quotient, Q, for a system is $1.6 \times 10 ^ { - 4 }$ . If the equilibrium constant for the system at some temperature is $8.5 \times 10 ^ { 3 }$ , what will happen as the reaction mixture returns to equilibrium?

A) The equilibrium constant will increase until it equals the reaction quotient.
B) There will be a net loss in both product(s) and reactant(s).
C) There will be a net loss in product(s).
D) There will be a net loss in reactant(s).
E) The equilibrium constant will increase.

Question 8

Which of the following is the correct balanced equation for the equilibrium constant expression given below?
$K = \left[ \mathrm { Pb } ^ { 2 + } \right] \left[ \mathrm { F } ^ { - } \right] ^ { 2 }$

A) PbF₂(aq) $\rightleftharpoons$ Pb(s) + F₂(aq)
B) PbF₂(s) $\rightleftharpoons$ Pb²⁺(aq) + 2 F^-(aq)
C) Pb²⁺(aq) + 2 F^-(aq) $\rightleftharpoons$ PbF₂(s)
D) Pb(s) + F₂(aq) $\rightleftharpoons$ PbF₂(aq)
E) PbF⁺(aq) + F^-(aq) $\rightleftharpoons$ PbF₂(aq)

Question 9

Write a balanced chemical equation which corresponds to the following equilibrium constant expression.
$K = \frac { \left[ \mathrm { NO } _ { 2 } ^ { - } \right] \left[ \mathrm { H } _ { 3 } \mathrm { O } ^ { + } \right] } { \left[ \mathrm { HNO } _ { 2 } \right] }$

A) HNO₂(aq) + H₂O( $\ell$ ) $\rightleftharpoons$ NO₂^-(aq) + H₃O⁺(aq)
B) NO₂^-(aq) + H₃O⁺(aq) $\rightleftharpoons$ HNO₂(aq) + H₂O( $\ell$ )
C) NO₂^-(aq) + H₃O⁺(aq) $\rightleftharpoons$ HNO₂(aq)
D) H⁺(aq) + OH^-(aq) $\rightleftharpoons$ H₂O( $\ell$ )
E) HNO₂(aq) $\rightleftharpoons$ NO₂^-(aq) + H₃O⁺(aq)

Question 10

For which of the following reactions is K_p = K_c?

A) 2 CO₂(g) $\rightleftharpoons$ 2 CO(g) + O₂(g)
B) CH₄(g) + 2 O₂(g) $\rightleftharpoons$ CO₂(g) + 2 H₂O(g)
C) C(s) + H₂O(g) $\rightleftharpoons$ H₂(g) + CO(g)
D) NH₃(g) $\rightleftharpoons$ 3/2 H₂(g) + 1/2 N₂(g)
E) 2 O₃(g) $\rightleftharpoons$ 3 O₂(g)

Question 11

Which of the following expressions for K is correct for the reaction given below? Al³⁺(aq) + 4 OH^-(aq) $\rightleftharpoons$ Al(OH)₄^-(aq)

A) $K = \frac { \left[ \mathrm { Al } ^ { 3 + } \right] \left[ \mathrm { OH } ^ { - } \right] } { \left[ \mathrm { Al } ( \mathrm { OH } ) _ { 4 } ^ { - } \right] }$
B) $K = \frac { \left[ \mathrm { Al } ( \mathrm { OH } ) _ { 4 } ^ { - } \right] } { \left[ \mathrm { OH } ^ { - } \right] ^ { 4 } }$
C) $K = \frac { \left[ \mathrm { Al } ( \mathrm { OH } ) _ { 4 } ^ { - } \right] } { \left[ \mathrm { Al } ^ { 3 + } \right] \left[ \mathrm { OH } ^ { - } \right] }$
D) $K = \frac { \left[ \mathrm { Al } ^ { 3 + } \right] \left[ \mathrm { OH } ^ { - } \right] ^ { 4 } } { \left[ \mathrm { Al } ( \mathrm { OH } ) _ { 4 } ^ { - } \right] }$
E) $K = \frac { \left[ \mathrm { Al } ( \mathrm { OH } ) _ { 4 } ^ { - } \right] } { \left[ \mathrm { Al } ^ { 3 + } \right] \left[ \mathrm { OH } ^ { - } \right] ^ { 4 } }$

Question 12

For the reaction 2NO(g) + O₂(g) $\rightleftharpoons$ 2NO₂(g) at 750°C, what is the relationship between K_c and K_p?

A) K_c = K_p
B) K_c = K_p × (RT)^-1
C) K_c = K_p = 1.0
D) K_c = K_p × (RT)^¾
E) K_c = K_p × (RT)¹

Question 13

If the reaction quotient, Q, is equal to K in a gas phase reaction, then

A) the chemical system has reached equilibrium.
B) the temperature must be increased for the reaction to proceed in the forward direction.
C) the reaction will proceed in the forward direction until equilibrium is established.
D) the reaction will proceed in the backward direction until equilibrium is established.
E) the reaction will proceed in the direction that increases the number of gas phase particles.

Question 14

If the reaction quotient, Q, is greater than K in a gas phase reaction, then

A) the chemical system has reached equilibrium.
B) the temperature must be increased for the reaction to proceed in the forward direction.
C) the reaction will proceed in the forward direction until equilibrium is established.
D) the reaction will proceed in the backward direction until equilibrium is established.
E) the reaction will proceed in the direction that increases the number of gas phase particles.

Question 15

Consider the formation of ozone by the following reaction.
3 O₂(g) $\rightleftharpoons$ 2 O₃(g)
Calculate the value of
K_p, given that K_c = 2.5 × 10^-29 at 298 K. (R = 0.08206 L?atm/mol ? K)

A) 1.0 × 10^-30
B) 2.1 × 10^-30
C) 2.5 × 10^-29
D) 3.3 × 10^-28
E) 6.1 ×10^-28

Question 16

What is the K_c equilibrium-constant expression for the following equilibrium? NiO(s) + H₂(g) $\rightleftharpoons$ Ni(s) + H₂O(g)

A) $\frac { \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] } { \left[ \mathrm { H } _ { 2 } \right] }$
B) ? $\frac { [ \mathrm { Ni } ] \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] } { \left[ \mathrm { H } _ { 2 } \right] }$
C) ? $\frac { [ \mathrm { Ni } ] \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] } { [ \mathrm { NiO } ] \left[ \mathrm { H } _ { 2 } \right] }$
D) ? $\frac { \left[ \mathrm { H } _ { 2 } \right] } { \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] }$
E) ? $\frac { [ \mathrm { NiO } ] \left[ \mathrm { H } _ { 2 } \right] } { [ \mathrm { Ni } ] \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] }$

Question 17

What is the K_c expression for the equilibrium given below?
CuI(s) $\rightleftharpoons$ Cu⁺(aq) + I?(aq)

A) $\left[ \mathrm { Cu } ^ { + } \right] \left[ \mathrm { I } ^ { - } \right]$
B) $\frac { \left[ \mathrm { Cu } ^ { + } \right] } { \left[ \mathrm { I } ^ { - } \right] }$
C) $\frac { \left[ \mathrm { Cu } ^ { + } \right] \left[ \mathrm { I } ^ { - } \right] } { [ \mathrm { CuI } ] }$
D) $\frac { [ \mathrm { CuI } ] } { \left[ \mathrm { Cu } ^ { + } \right] \left[ \mathrm { I } ^ { - } \right] }$
E) $\frac { 1 } { \left[ \mathrm { Cu } ^ { + } \right] \left[ \mathrm { I } ^ { - } \right] }$

Question 18

What is the expression for K_c for the following equilibrium?
CaSO₃(s) $\rightleftharpoons$ CaO(s) + SO₂(g)

A) $[ \mathrm { CaO } ] \left[ \mathrm { SO } _ { 2 } \right]$
B) ? $\left[ \mathrm { SO } _ { 2 } \right]$
C) ? $\frac { [ \mathrm { CaO } ] \left[ \mathrm { SO } _ { 2 } \right] } { \left[ \mathrm { CaSO } _ { 3 } \right] }$
D) ? $\frac { \left[ \mathrm { CaSO } _ { 3 } \right] } { [ \mathrm { CaO } ] \left[ \mathrm { SO } _ { 2 } \right] }$
E) ? $\frac { 1 } { \left[ \mathrm { SO } _ { 2 } \right] }$

Question 19

Which of the following is the correct balanced equation for the equilibrium constant expression given below?
$K _ { \mathrm { p } } = \frac { P _ { \mathrm { HI } } ^ { 2 / 2 } } { P _ { \mathrm { H } _ { 2 } } ^ { 1 / 2 } P _ { \mathrm { I } _ { 2 } } ^ { 1 / 2 } }$

A) $\frac { 1 } { 2 }$ H₂(g) + $\frac { 1 } { 2 }$ I₂(g) $\rightleftharpoons$ HI(g)
B) HI(g) $\rightleftharpoons$ $\frac { 1 } { 2 }$ H₂(g) + $\frac { 1 } { 2 }$ I₂(g)
C) $\frac { 1 } { 2 }$ H₂(aq) + $\frac { 1 } { 2 }$ I₂(aq) $\rightleftharpoons$ HI(aq)
D) HI(aq) $\rightleftharpoons$ $\frac { 1 } { 2 }$ H₂(aq) + $\frac { 1 } { 2 }$ I₂(aq)
E) 2 HI(g) $\rightleftharpoons$ H₂(g) + I₂(g)

Question 20

Which of the following expressions correctly describes the equilibrium constant K_c for the reaction given below?
2 C₂H₂(g) + 5 O₂(g) $\rightleftharpoons$ 4 CO₂(g) + 2 H₂O(g)

A) $K _ { \mathrm { c } } = \frac { \left[ \mathrm { CO } _ { 2 } \right] \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] } { \left[ \mathrm { C } _ { 2 } \mathrm { H } _ { 2 } \right] \left[ \mathrm { O } _ { 2 } \right] }$
B) $K _ { \mathrm { c } } = \frac { \left[ \mathrm { C } _ { 2 } \mathrm { H } _ { 2 } \right] ^ { 2 } \left[ \mathrm { O } _ { 2 } \right] ^ { 5 } } { \left[ \mathrm { CO } _ { 2 } \right] ^ { 4 } \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] ^ { 2 } }$
C) $K _ { \mathrm { c } } = \frac { \left[ \mathrm { CO } _ { 2 } \right] ^ { 4 } \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] ^ { 2 } } { \left[ \mathrm { C } _ { 2 } \mathrm { H } _ { 2 } \right] ^ { 2 } \left[ \mathrm { O } _ { 2 } \right] ^ { 5 } }$
D) $K _ { \mathrm { c } } = \frac { 4 \left[ \mathrm { CO } _ { 2 } \right] + 2 \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] } { 2 \left[ \mathrm { C } _ { 2 } \mathrm { H } _ { 2 } \right] + 5 \left[ \mathrm { O } _ { 2 } \right] }$
E) $K _ { \mathrm { c } } = \frac { 2 \left[ \mathrm { C } _ { 2 } \mathrm { H } _ { 2 } \right] + 5 \left[ \mathrm { O } _ { 2 } \right] } { 4 \left[ \mathrm { CO } _ { 2 } \right] + 2 \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] }$

Question 21

An aqueous mixture of phenol and ammonia has initial concentrations of 0.200 M C₆H₅OH(aq) and 0.120 M NH₃(aq). At equilibrium, the C₆H₅O^-(aq) concentration is 0.050 M. Calculate the equilibrium constant, K, for the reaction below. C₆H₅OH(aq) + NH₃(aq) $\rightleftharpoons$ C₆H₅O^- + NH₄⁺(aq)

A) 0.10
B) 0.24
C) 2.1
D) 4.2
E) 4.8

Question 22

A 3.50-mol sample of HI is placed in a 1.00-L vessel at 460°C, and the reaction system is allowed to come to equilibrium. The HI partially decomposes, forming 0.266 mol H₂ and 0.266 mol I₂ at equilibrium. What is the equilibrium constant K_c for the following reaction at 460°C?
½ H₂(g) + ½ I₂(g) $\rightleftharpoons$ HI(g)

A) 1.23 × 10²
B) 8.10 × 10^-3
C) 2.40 × 10^-2
D) 11.1
E) 6.45

Question 23

For the reaction given below, 2.00 moles of A and 3.00 moles of B are placed in a 6.00-L container. A(g) + 2B(g) $\rightleftharpoons$ C(g)
At equilibrium, the concentration of A is 0.230 mol/L. What is the value of K_c?

A) 1.20
B) 1.53
C) 5.22
D) 0.230
E) 0.449

Question 24

Consider the reaction below. 2 HF(g) $\rightleftharpoons$ H₂(g) + F₂(g) (K_c = 1.00 × 10^-2)
Given that 1.00 mol of HF(g), 0.241 mol of H₂(g), and 0.750 mol of F₂(g) are mixed in a 5.00 L flask, determine the reaction quotient, Q.

A) Q = 0.0452
B) Q = 0.181
C) Q = 0.0362
D) Q = 1.99
E) None of these

Question 25

Consider the following equilibrium:
C₂H₆(g) + C₅H₁₂(g) $\rightleftharpoons$ CH₄(g) + C₆H₁₄(g); K_p = 9.57 at 500 K
Suppose 22.7 g each of CH₄, C₂H₆, C₅H₁₂, and C₆H₁₄ are placed in a 35.0-L reaction vessel at 500 K. Which of the following statements is correct?

A) Because Q_c < K_c, more products will be formed.
B) Because Q_c = 1, the system is at equilibrium.
C) Because Q_c = 1, more products will be formed.
D) Because Q_c = 1, more reactants will be formed.
E) Because Q_c > K_c, more reactants will be formed.

Question 26

Which of the following statements about the reaction quotient, Q, is false?

A) The value of Q can be used to predict equilibrium concentrations.
B) It has the same expression as K_c.
C) Its value is calculated using nonequilibrium concentrations.
D) If Q > K_c, the reaction must move to equilibrium by forming more reactants.
E) If Q < K_c, the reaction must move to equilibrium by forming more products.

Question 27

The following reaction occurred when a 1.0-liter reaction vessel was initially charged with 2.0 moles of N₂(g) and 4.0 moles of H₂(g): 3H₂(g) + N₂(g) $\rightleftharpoons$ 2NH₃(g)
Once equilibrium was established, the concentration of NH₃(g) was determined to be 0.57 M at 700.°C. The value for K_c at 700.°C for the formation of ammonia is:

A) 3.2 × 10^-1
B) 6.1 × 10^-3
C) 1.1 × 10^-1
D) 6.0 × 10^-2
E) none of these

Question 28

Exactly 1.0 mol N₂O₄ is placed in an empty 1.0-L container and allowed to reach equilibrium described by the equation N₂O₄(g) $\rightleftharpoons$ 2NO₂(g). If at equilibrium the N₂O₄ is 27.0% dissociated, what is the value of the equilibrium constant, K_c, for the reaction under these conditions?

A) 0.40
B) 2.5
C) 0.29
D) 0.74
E) 0.10

Question 29

A 10.0 g sample of solid NH₄Cl is heated in a 5.00 L container to 900 °C. At equilibrium, the pressure of NH₃(g) is 1.17 atm. Calculate the equilibrium constant, Kp, for the reaction below. NH₄Cl(s) $\rightleftharpoons$ NH₃(g) + HCl(g)

A) 1.37
B) 4.93
C) 1.17
D) 2.34
E) None of these

Question 30

A 2.5 L flask is filled with 0.25 mol SO₃, 0.20 mol SO₂, and 0.40 mol O₂, and allowed to reach equilibrium. Assume the temperature of the mixture is chosen so that K_c = 0.12. Predict the effect on the concentration of SO₃ as equilibrium is achieved by using Q, the reaction quotient. 2 SO₃(g) $\rightleftharpoons$ 2 SO₂(g) + O₂(g)

A) [SO₃] will decrease because Q > K.
B) [SO₃] will decrease because Q < K.
C) [SO₃] will increase because Q < K.
D) [SO₃] will increase because Q > K.
E) [SO₃] will remain the same because Q = K.

Question 31

Consider the reaction A(aq) $\rightleftharpoons$ 2 B(aq) where K_c = 4.1 at 25 °C. If 0.50 M A(aq) and 1.5 M B(aq) are initially present in a 1.0 L flask at 25 °C, what change in concentrations (if any) will occur in time?

A) [A] will decrease and [B] will decrease.
B) [A] will decrease and [B] will increase.
C) [A] will increase and [B] will decrease.
D) [A] will increase and [B] will increase.
E) [A] and [B] remain unchanged.

Question 32

What is the reaction quotient, Q, for the equilibrium
CuCl(s) $\rightleftharpoons$ Cu⁺(aq) + Cl?(aq)
When 0.3746 L of $4.359 \times 10 ^ { - 4 }$ M Cu⁺ is combined with 0.4326 L of $8.718 \times 10 ^ { - 4 }$ M Cl? in the presence of an excess of CuCl(s)?

A) $9.451 \times 10 ^ { - 8 }$
B) $3.8 \times 10 ^ { - 7 }$
C) $6.158 \times 10 ^ { - 8 }$
D) $7.629 \times 10 ^ { - 8 }$
E) $2.476 \times 10 ^ { - 7 }$

Question 33

At a high temperature, equal concentrations of 0.160 mol/L of H₂(g) and I₂(g) are initially present in a flask. The H₂ and I₂ react according to the balanced equation below. H₂(g) + I₂(g) $\rightleftharpoons$ 2 HI(g)
When equilibrium is reached, the concentration of H₂(g) has decreased to 0.036 mol/L. What is the equilibrium constant, K_c, for the reaction?

A) 3.4
B) 4.0
C) 12
D) 22
E) 48

Question 34

At a given temperature, 0.0664 mol N₂O₄(g) is placed in a 1.00 L flask. After reaching equilibrium, the concentration of NO₂(g) is 6.1 × 10^-3 M. What is K_c for the reaction below?
N₂O₄(g) $\rightleftharpoons$ 2 NO₂(g)

A) 3.7 ×10^-5
B) 1.4 ×10^-4
C) 5.9 × 10^-4
D) 9.6 × 10^-2
E) 1.8 × 10³

Question 35

A 3.00-liter flask initially contains 3.00 mol of gas A and 1.50 mol of gas B. Gas A decomposes according to the following reaction: 3A $\rightleftharpoons$ 2B + C
The equilibrium concentration of gas C is 0.134 mol/L. Determine the value of the equilibrium constant, K_c.

A) 0.172
B) 0.132
C) 3.19 × 10^-3
D) 0.370
E) none of these

Question 36

Nitrogen trifluoride decomposes at to form nitrogen and fluorine gases according to the following equation: 2NF₃(g) $\rightleftharpoons$ N₂(g) + 3F₂(g)
2)50-L reaction vessel is initially charged with 1.22 mol of NF₃ and allowed to come to equilibrium at 800 K. Once equilibrium is established, the reaction vessel is found to contain 0.0194 mol of N₂. What is the value of K_p at this temperature? (R = 0.0821 L?atm/mol?K)

A) 2.68 × 10^-6
B) 1.91 × 10^-3
C) 1.79 × 10^-3
D) 2.77 × 10^-6
E) 4.43 × 10^-7

Question 37

At 25 °C, 0.138 mg AgBr dissolves in 10.0 L of water. What is the equilibrium constant for the reaction below?
AgBr(s) $\rightleftharpoons$ Ag⁺(aq) + Br^-(aq)

A) 5.40 × 10^-13
B) 5.40 × 10^-11
C) 1.90 × 10^-8
D) 7.35 × 10^-7
E) 1.90 × 10^-6

Question 38

Excess Ag₂SO₄(s) is placed in water at 25 °C. At equilibrium, the solution contains 0.029 M Ag⁺(aq). What is the equilibrium constant for the reaction below?
Ag₂SO₄(s) $\rightleftharpoons$ 2 Ag⁺(aq) + SO₄^2-(aq)

A) 1.8 × 10^-7
B) 6.1 × 10^-6
C) 1.2 × 10^-5
D) 2.4 × 10^-5
E) 8.4 × 10^-4

Question 39

When 0.20 mole HF is dissolved in water to a volume of 1.00 L, 5.8% of the HF dissociates to form F^-(aq). What is the equilibrium constant for the reaction? HF(aq) + H₂O( $\ell$ ) $\rightleftharpoons$ F^-(aq) + H₃O⁺(aq)

A) 1.3 × 10^-4
B) 7.1 × 10^-4
C) 1.2 × 10^-2
D) 1.7 × 10^-2
E) 6.2 × 10^-2

Question 40

A sample of solid NH₄NO₃ was placed in an evacuated container and then heated so that it decomposed explosively according to the following equation: NH₄NO₃(s) $\rightleftharpoons$ N₂O(g) + 2H₂O(g)
At equilibrium the total pressure in the container was found to be 2.72 atm at a temperature of 500.°C. Calculate K_p.

A) 1.64
B) 0.822
C) 2.98
D) 80.5
E) 0.745

Question 41

Given the following chemical equilibria, N₂(g) + O₂(g) $\rightleftharpoons$ 2 NO(g)
K₁
N₂(g) + 3 H₂(g) $\rightleftharpoons$ 2 NH₃(g)
K₂
H₂(g) + 1/2 O₂(g) $\rightleftharpoons$ H₂O(g)
K₃
Determine the method used to calculate the equilibrium constant for the reaction below.
4 NH₃(g) + 5 O₂(g) $\rightleftharpoons$ 4 NO(g) + 6 H₂O(g)
K _c

A) $K _ { \mathrm { c } } = K _ { 1 } \times K _ { 2 } \times K _ { 3 }$
B) $K _ { \mathrm { c } } = \frac { K _ { 1 } ^ { 2 } K _ { 3 } ^ { 6 } } { K _ { 2 } ^ { 2 } }$
C) $K _ { \mathrm { c } } = 2 K _ { 1 } - 2 K _ { 2 } + 3 K _ { 3 }$
D) $K _ { \mathrm { c } } = \frac { 6 \left( K _ { 1 } \times K _ { 3 } \right) } { 2 K _ { 2 } }$
E) $K _ { \mathrm { c } } = \frac { K _ { 1 } ^ { 2 } \times K _ { 2 } ^ { 2 } } { K _ { 3 } ^ { 3 } }$

Question 42

Given the equilibrium constants for the following reactions:
4Cu(s) + O₂(g) $\rightleftharpoons$ 2Cu₂O(s), K₁
4CuO(s) $\rightleftharpoons$ 2Cu₂O(s) + O₂(g), K₂
What is K for the system
2Cu(s) + O₂(g) $\rightleftharpoons$ 2CuO(s)
Equivalent to?

A) $\left( K _ { 1 } \right) ^ { 1 / 2 } / \left( K _ { 2 } \right)$ $\left[ \left( K _ { 1 } \right) / \left( K _ { 2 } \right) \right] ^ { 1 / 2 }$
B) $\left( K _ { 2 } \right) \left( K _ { 1 } \right) ^ { 1 / 2 }$
C) (K₁)(K₂)
D) $\left( K _ { 2 } \right) ^ { 1 / 2 } / \left( K _ { 1 } \right)$ $\left[ \left( K _ { 2 } \right) / \left( K _ { 1 } \right) \right] ^ { 1 / 2 }$
E) $\left( K _ { 1 } \right) \left( K _ { 2 } \right) ^ { 1 / 2 }$

Question 43

In an experiment, 0.46 mol H₂ and 0.46 mol I₂ are mixed in a 1.00-L container, and the reaction forms HI. If K_c = 49. for this reaction, what is the equilibrium concentration of HI? I₂(g) + H₂(g) $\rightleftharpoons$ 2HI(g)

A) 0.88 M
B) 0.81 M
C) 0.72 M
D) 0.115 M
E) 0.061 M

Question 44

Nitrogen and oxygen gases may react to form nitrogen monoxide. At 1500 °C, K_c equals 1.0 × 10?⁵. N₂(g) + O₂(g) $\rightleftharpoons$ 2 NO(g)
If 0.030 mol N₂ and 0.030 mol O₂ are sealed in a 1.0 L flask at 1500 °C, what is the concentration of NO(g) when equilibrium is established?

A) 3.0 × 10?⁷ M
B) 4.7 × 10?⁵ M
C) 9.5 × 10?⁵ M
D) 3.0 × 10?² M
E) 9.1 × 101 M

Question 45

For the reaction N₂O₄(g) $\rightleftharpoons$ 2NO₂(g), K_p = 0.148 at a temperature of 298 K. What is K_p for the following reaction? 12NO₂(g) $\rightleftharpoons$ 6N₂O₄(g)

A) 9.52 × 10⁴
B) 0.888
C) 1.05 × 10^-5
D) 1.13
E) 6.76

Question 46

Consider the following equilibrium:
CO₂(g) + H₂(g) $\rightleftharpoons$ CO(g) + H₂O(g); K_c = 1.6 at 1260 K
Suppose 0.019 mol CO₂ and 0.030 mol H₂ are placed in a 3.00-L vessel at 1260 K. What is the equilibrium partial pressure of CO(g)? (R = 0.0821 L · atm/K·mol)

A) 4 atm
B) 0.35 atm
C) 1.6 atm
D) 0.66 atm
E) 1 atm

Question 47

Sulfuryl chloride decomposes to sulfur dioxide and chlorine.
SO₂Cl₂(g) $\rightleftharpoons$ SO₂(g) + Cl₂(g)
K_c is 0.045 at 648 K. If an initial concentration of 0.075 M SO₂Cl₂ is allowed to equilibrate, what is the equilibrium concentration of Cl₂?

A) 0.0034 M
B) 0.030 M
C) 0.040 M
D) 0.058 M
E) 0.075 M

Question 48

At a given temperature, K = 0.024 for the equilibrium:
PCl₅(g) $\rightleftharpoons$ PCl₃(g) + Cl₂(g)
What is K for:
Cl₂(g) + PCl₃(g) $\rightleftharpoons$ PCl₅(g)?

A) 1700
B) 24
C) 0.00058
D) 42
E) 0.024

Question 49

At 700 K, K_p for the following equilibrium is
5.6 × 10^-3. 2HgO(s) $\rightleftharpoons$ 2Hg(l) + O₂(g)
Suppose 43.1 g of mercury(II) oxide is placed in a sealed 4.00-L vessel at 700 K. What is the partial pressure of oxygen gas at equilibrium?
(R = 0.0821 L · atm/(K · mol))

A) 0.074 atm
B) 0.0056 atm
C) 2.8 atm
D) 14 atm
E) 1.4 atm

Question 50

If K_c = 0.124 for A₂ + 2B $\rightleftharpoons$ 2AB, what is the value of K_c for the reaction 4AB $\rightleftharpoons$ 2A₂ + 4B?

A) 0.124
B) 0.248
C) 65.0
D) -0.124
E) 4.03

Question 51

The equilibrium constant at 25 °C for the dissolution of silver iodide is
8.5 × 10^-17. AgI(s) $\rightleftharpoons$ Ag⁺(aq) + I^-(aq)
If an excess quantity of AgI(s) is added to water and allowed to equilibrate, what is the equilibrium concentration of I^-?

A) 7.2 × 10^-33 M
B) 4.3 × 10^-17 M
C) 8.5 × 10^-17 M
D) 6.5 × 10^-9 M
E) 9.2 × 10^-9 M

Question 52

For the equilibrium N₂O₄(g) $\rightleftharpoons$ 2NO₂(g), at 298 K, K_p = 0.15. For this reaction system, it is found that the partial pressure of N₂O₄ is 3.7 × 10^-2 atm at equilibrium. What is the partial pressure of NO₂ at equilibrium?

A) 4.9 atm
B) 24 atm
C) 0.0016 atm
D) 0.0055 atm
E) 0.074 atm

Question 53

A mixture of nitrogen and hydrogen was allowed to come to equilibrium at a given temperature. 3H₂ + N₂ $\rightleftharpoons$ 2NH₃
An analysis of the mixture at equilibrium revealed 2.1 mol N₂, 2.8 mol H₂, and 1.8 mol NH₃. How many moles of H₂ were present at the beginning of the reaction?

A) 2.8
B) 4.2
C) 4.6
D) 5.5
E) 4.0

Question 54

Consider the reaction H₂ + I₂ $\rightleftharpoons$ 2HI for which K_c = 44.0 at a high temperature. If an equimolar mixture of reactants gives the concentration of the product to be 0.50 M at equilibrium, determine the equilibrium concentration of the hydrogen.

A) 7.5 × 10^-2 M
B) 1.1 × 10^-1 M
C) 3.8 × 10^-2 M
D) 1.3 × 10¹ M
E) 5.7 × 10^-3 M

Question 55

Nitrosyl bromide decomposes according to the chemical equation below. 2 NOBr(g) $\rightleftharpoons$ 2 NO(g) + Br₂(g)
When 0.260 atm of NOBr is sealed in a flask and allowed to reach equilibrium, 22% of the NOBr decomposes. What is the equilibrium constant, K_p, for the reaction?

A) 2.3 × 10^-3
B) 4.5 × 10^-3
C) 3.5 × 10^-2
D) 4.8 × 10^-2
E) 8.0 × 10^-2

Question 56

The equilibrium constant (K_c) for the decomposition of ammonium hydrogen sulfide, NH₄HS(s) $\rightleftharpoons$ NH₃(g) + H₂S(g), is 1.8 × 10^-4 at 25 °C. If excess NH₄HS(s) is allowed to equilibrate at 25 °C, what is the equilibrium concentration of NH₃?

A) 3.2 × 10^-8 M
B) 9.0 × 10^-5 M
C) 1.8 × 10^-4 M
D) 6.7 × 10^-3 M
E) 1.3 × 10^-2 M

Question 57

For the equilibrium PCl₅(g) $\rightleftharpoons$ PCl₃(g) + Cl₂(g), K_c = 2.0 × 10¹ at 240°C. If pure PCl₅ is placed in a 1.00-L container and allowed to come to equilibrium, and the equilibrium concentration of PCl₃(g) is 0.50 M, what is the equilibrium concentration of PCl₅(g)?

A) 1 M
B) 0.25 M
C) 0.025 M
D) 0.012 M
E) 6.3 M

Question 58

At 800 K, the equilibrium constant, K_p, for the following reaction is 3.2 × 10^-7. 2 H₂S(g) $\rightleftharpoons$ 2 H₂(g) + S₂(g)
A reaction vessel at 800 K initially contains 3.00 atm of H₂S. If the reaction is allowed to equilibrate, what is the equilibrium pressure of S₂?

A) 8.5 × 10^-5 atm
B) 6.2 × 10^-3 atm
C) 9.0 × 10^-3 atm
D) 1.1 × 10^-2 atm
E) 1.4 × 10^-2 atm

Question 59

At 25 °C, the decomposition of dinitrogen tetraoxide
N₂O₄(g) $\rightleftharpoons$ 2 NO₂(g)
Has an equilibrium constant (K_p) of 0.144. At equilibrium, the total pressure of the system is 0.0758 atm. What is the partial pressure of each gas?

A) 0.0745 atm NO₂(g) and 0.0385 N₂O₄(g)
B) 0.0549 atm NO₂(g) and 0.0209 N₂O₄(g)
C) 0.0531 atm NO₂(g) and 0.0227 N₂O₄(g)
D) 0.0502 atm NO₂(g) and 0.0256 N₂O₄(g)
E) 0.0381 atm NO₂(g) and 0.0377 N₂O₄(g)

Question 60

For the equilibrium PCl₅(g) $\rightleftharpoons$ PCl₃(g) + Cl₂(g), K_c = 4.0 at 228°C. If pure PCl₅ is placed in a 1.00-L container and allowed to come to equilibrium, and the equilibrium concentration of PCl₅(g) is 0.19 M, what is the equilibrium concentration of PCl₃?

A) 0.095 M
B) 0.4 M
C) 0.19 M
D) 0.87 M
E) 0.009 M

Question 61

Consider the following equilibria.
PbBr₂(s) $\rightleftharpoons$ Pb²⁺(aq) + 2 Br^-(aq)
K₁ = 6.6 × 10^-6
Pb(OH)₂(s) $\rightleftharpoons$ Pb²⁺(aq) + 2 OH^-(aq)
K₂ = 1.4 × 10^-15
Determine the equilibrium constant, K_c, for the reaction below.
PbBr₂(s) + 2 OH^-(aq) $\rightleftharpoons$ Pb(OH)₂(s) + 2 Br^-(aq)

A) 9.2 × 10^-21
B) 2.1 × 10^-10
C) 6.6 × 10^-6
D) 4.7 × 10⁹
E) 1.1 × 10²⁰

Question 62

In 1913, the Haber-Bosch process was patented. The product of the Haber-Bosch process is ________.

Question 63

The thermochemical equation for the formation of ammonia from elemental nitrogen and hydrogen is as follows. N₂(g) + 3 H₂(g) $\rightleftharpoons$ 2 NH₃(g)
?H = -92.2 kJ
Given a system that is initially at equilibrium, which of the following actions cause the reaction to proceed to the left?

A) adding N₂(g)
B) removing NH₃(g)
C) adding a catalyst
D) decreasing the temperature
E) removing H₂(g)

Question 64

When the pressure of an equilibrium mixture of SO₂, O₂, and SO₃ is doubled at constant temperature, what the effect on K_p?
2SO₂(g) + O₂(g) $\rightleftharpoons$ 2SO₃(g)

A) K_p is halved.
B) K_p is doubled.
C) K_p is unchanged.
D) K_p is tripled.
E) K_p is decreased by a third.

Question 65

Which of the following equilibria would not be affected by pressure change at constant temperature?

A) CO₂(g) + H₂(g) $\rightleftharpoons$ CO(g) + H₂O(g)
B) CO(g) + $\frac { 1 } { 2 }$ O₂(g) $\rightleftharpoons$ CO₂(g)
C) 2 Hg( $\ell$ ) + O₂(g) $\rightleftharpoons$ 2 HgO(s)
D) 2 H₂(g) + O₂(g) $\rightleftharpoons$ 2 H₂O( $\ell$ )
E) CaCO₃(s) $\rightleftharpoons$ CaO(s) + CO₂(g)

Question 66

The standard enthalpy of formation of ammonia is -46.1 kJ/mol.
1/2 N₂(g) + 3/2 H₂(g) NH₃(g)
Commercially, the reaction is carried out at high temperatures. Using your knowledge of kinetics and equilibrium, explain an advantage and a disadvantage of synthesizing ammonia at high temperatures.

Question 67

In which of the following reactions does a decrease in the volume of the reaction vessel at constant temperature favor the formation of the products?

A) 2 H₂(g) + O₂(g) $\rightleftharpoons$ 2 H₂O(g)
B) NO₂(g) + CO(g) $\rightleftharpoons$ NO(g) + CO₂(g)
C) H₂(g) + I₂(g) $\rightleftharpoons$ 2 HI(g)
D) 2 O₃(g) $\rightleftharpoons$ 3 O₂(g)
E) MgCO₃(s) $\rightleftharpoons$ MgO(s) + CO₂(g)

Question 68

When 1.0 mole of acetic acid is diluted with water to a volume of 1.0 L at 25 °C, 0.42% of the acetic acid ionizes to form acetate ion and hydronium ion.
CH₃CO₂H(aq) + H₂O( ) CH₃CO₂^-(aq) + H₃O⁺(aq)
What percentage of the acid ionizes when 0.75 mole of acetic acid is diluted with water to 1.0 L at 25 °C?

Question 69

Given the following equilibria,
Ni²⁺(aq) + 2 OH^-(aq) $\rightleftharpoons$ Ni(OH)₂(s)
K₁ = 1.8 × 10¹⁵
Ni²⁺(aq) + 4 CN^-(aq) $\rightleftharpoons$ Ni(CN)₄^2-(aq)
K₂ = 2.0 × 10³¹
Determine the equilibrium constant, K_c, for the following reaction.
Ni(OH)₂(s) + 4 CN^-(aq) $\rightleftharpoons$ Ni(CN)₄^2-(aq) + 2 OH^-(aq)

A) 2.8 × 10^-47
B) 9.0 × 10^-17
C) 1.8 × 10¹⁵
D) 1.1 × 10¹⁶
E) 3.6 × 10⁴⁶

Question 70

Consider the following equilibrium. PCl₃(g) + Cl₂(g) $\rightleftharpoons$ PCl₅(g) ?H = -92 kJ
The concentration of PCl₃ at equilibrium can be increased by:

A) decreasing the temperature.
B) adding Cl₂ to the system.
C) adding PCl₅ to the system.
D) increasing the pressure.
E) adding a catalyst.

Question 71

Which of the following statements is true if reaction quotient (Q) is greater than equilibrium constant (K)?

A) Reactant concentrations will increase.
B) Product concentrations will increase.
C) Reactants will convert to products.
D) Standard enthalpy of formation of products decreases.
E) Standard enthalpy of formation of reactants increases.

Question 72

If a stress is applied to an equilibrium system, the system will respond in such a way as to relieve that stress. This is a statement of ________ principle.

Question 73

Given the equilibrium constants for the equilibria, NH₄⁺(aq) + H₂O(l) $\rightleftharpoons$ NH₃(aq) + H₃O⁺(aq); K_c = $5.69 \times 10 ^ { - 10 }$ 2H₂O(l) $\rightleftharpoons$ 2H₃O⁺(aq); K_c = $3.06 \times 10 ^ { - 10 }$ determine K_c for the following equilibrium.
CH₃COOH(aq) + NH₃(aq) $\rightleftharpoons$ CH₃COO?(aq) + NH₄⁺(aq)

A) 3.08 × 10⁴
B) 3.25 × 10^-5
C) 9.96 × 10^-15
D) 1.00 × 10¹⁴
E) 1.75 × 10^-5

Question 74

The symbol Q is called the ________.

Question 75

Assume that the following chemical reaction is at equilibrium.
2 ICl(g) $\rightleftharpoons$ I₂(g) + Cl₂(g)
?H° = +26.9 kJ
At 25 °C, K_p = 2.0 × 10⁵. If the temperature is increase to 45 °C, which statement applies?

A) K_p will decrease and the reaction will proceed in the backward direction.
B) K_p will decrease and the reaction will proceed in the forward direction.
C) K_p will remain unchanged and the reaction will proceed in the forward direction.
D) K_p will increase and the reaction will proceed in the backward direction.
E) K_p will increase and the reaction will proceed in the forward direction.