Deck 15: Chemical Equilibrium: How Much Product Does a Reaction Really Make

Question 1

Identify the equilibrium expression for the following reaction, assuming homogeneity:
Boy + girl $\leftrightarrows$ Couple

A) $K = \frac { [ \text { boy } ] [ \text { girl } ] } { [ \text { couple } ] }$
B) $K = \frac { [ \text { boy } ] + [ \text { girl } ] } { [ \text { couple } ] }$
C) $K = [ \text { boy } ] [ \text { girl } ] [ \text { couple } ]$
D) $K = \frac { [ \text { couple } ] } { [ \text { boy } ] [ \text { girl } ] }$
E) $K = [ \text { couple } ] - [ \text { boy } ] - [ \text { girl } ]$

Answer 1

$K = \frac { [ \text { couple } ] } { [ \text { boy } ] [ \text { girl } ] }$

Question 2

A chemical equilibrium
2 A $\leftrightarrows$ B
Has a forward rate constant, k_f = 10 M ^-1s^-1, and a reverse rate constant, k_r = 5.0 s^-1. What is the value of the equilibrium constant for this system?

A) 0.5
B) 2.0
C) 20
D) 0.050
E) 5.0

Answer 2

2.0

Question 3

At a high temperature, carbon dioxide decomposes to produce carbon monoxide and oxygen. When equilibrium is established, which, if any, of the following ratios is constant and independent of the initial concentration of carbon dioxide and whether or not oxygen was present initially?
CO₂(g) $\leftrightarrows$ CO(g) +1/2 O₂(g)

A) $\frac { \left[ \mathrm { CO } _ { 2 } \right] } { [ \mathrm { CO } ] \left[ \mathrm { O } _ { 2 } \right] }$
B) $\frac { \left[ \mathrm { CO } _ { 3 } \right] \left[ \mathrm { O } _ { 2 } \right] } { \left[ \mathrm { CO } _ { 2 } \right] }$
C) $\frac { [ \mathrm { CO } ] \left[ \frac { 1 } { 2 } \mathrm { O } _ { 2 } \right] } { \left[ \mathrm { CO } _ { 2 } \right] }$
D) $\frac { \left[ \mathrm { CO } ^ { 2 } \left[ \mathrm { O } _ { 2 } \right] \right. } { \left[ \mathrm { CO } _ { 2 } \right] ^ { 2 } }$
E) None of these ratios correctly describes the equilibrium concentrations.

Answer 3

$\frac { \left[ \mathrm { CO } ^ { 2 } \left[ \mathrm { O } _ { 2 } \right] \right. } { \left[ \mathrm { CO } _ { 2 } \right] ^ { 2 } }$

Question 4

The forward rate constant, k_f, and reverse rate constant, k_r, for a chemical reaction are not equal. Which of the following must be true?

A) The reaction will be unable to achieve equilibrium.
B) k_f and k_r will become equal as equilibrium is approached owing to concentration changes.
C) k_f and k_r will become equal as equilibrium is approached owing to temperature changes.
D) k_f and k_r will remain unequal but the rates will become equal owing to concentration changes.
E) k_f and k_r will remain unequal but the rates will become equal owing to temperature changes.

Question 5

At a high temperature, carbon dioxide decomposes to produce carbon monoxide and oxygen. Which expression corresponds to the equilibrium constant for the reaction written as
CO₂(g) $\leftrightarrows$ CO(g) +1/2 O₂(g)?

A) $\frac { \left[ \mathrm { CO } _ { 2 } \right] } { [ \mathrm { CO } ] \left[ \mathrm { O } _ { 2 } \right] }$
B) $\frac { \left[ \mathrm { CO } _ { 3 } \right] \left[ \mathrm { O } _ { 2 } \right] } { \left[ \mathrm { CO } _ { 2 } \right] }$
C) $\frac { [ \mathrm { CO } ] \left[ \frac { 1 } { 2 } \mathrm { O } _ { 2 } \right] } { \left[ \mathrm { CO } _ { 2 } \right] }$
D) $\frac { [ \mathrm { CO } ] \left[ \mathrm { O } _ { 2 } \right] ^ { 1 / 2 } } { \left[ \mathrm { CO } _ { 2 } \right] }$
E) $\frac { \frac { 1 } { 2 } [ \mathrm { CO } ] \left[ \mathrm { O } _ { 2 } \right] } { \left[ \mathrm { CO } _ { 2 } \right] }$

Question 6

Which of the following can be predicted from the law of mass action?
I. At equilibrium, the ratio of concentrations of products to reactants, each raised to a power corresponding to the stoichiometric coefficient in the balanced reaction equation, will have a constant value at a given temperature.
II. The direction of the reaction given values for the reactant and product concentrations and the equilibrium constant.
III. The amounts of products that can be produced from a given amount of reactants.

A) I only
B) II and III
C) I, II, and III
D) I and II
E) I and III

Question 7

Write the equilibrium expression for the reaction
Zn²⁺(aq) + 2 NH₃(aq) $\leftrightarrows$ Zn(NH₃)²⁺(aq)

A) $K = \left[ \mathrm { Zn } ^ { 2 + } \right] + 2 \left[ \mathrm { NH } _ { 3 } \right] + \left[ \mathrm { Zn } \left( \mathrm { NH } _ { 3 } \right) ^ { 2 + } \right]$
B) $K = \frac { \left[ \mathrm { Zn } ^ { 2 + } \right] + 2 \left[ \mathrm { NH } _ { 3 } \right] } { \left[ \mathrm { Zn } \left( \mathrm { NH } _ { 3 } \right) ^ { 2 + } \right] }$
C) $K = \frac { \left[ \mathrm { Zn } ^ { 2 + } \right] \left[ \mathrm { NH } _ { 3 } \right] ^ { 2 } } { \left[ \mathrm { Zn } \left( \mathrm { NH } _ { 3 } \right) ^ { 2 + } \right] }$
D) $K = \frac { \left[ \mathrm { Zn } \left( \mathrm { NH } _ { 3 } \right) ^ { 2 + } \right] } { \left[ \mathrm { Zn } ^ { 2 + } \right] \left[ \mathrm { NH } _ { 3 } \right] ^ { 2 } }$
E) $K = \left[ \mathrm { Zn } \left( \mathrm { NH } _ { 3 } \right) ^ { 2 + } \right] - \left[ \mathrm { Zn } ^ { 2 + } \right] - 2 \left[ \mathrm { NH } _ { 3 } \right]$

Question 8

For an equilibrium reaction with K = 1.2 * 10⁸, the forward rate constant was found to be 3.5 *10⁵. What is the value of the reverse rate constant?

A) 3.5 * 10⁵
B) 3.4 * 10²
C) 4.2 *10¹³
D) 2.9 *10^-3
E) 6.0 * 10^-5

Question 9

Which of the following is true for a chemical reaction at equilibrium regarding the concentration of products?

A) They will not change because there are no more reactants.
B) They will not change because the limiting reagent is gone.
C) They will not change because this is a constant for each reaction.
D) They will not change because the forward and reverse rates are equal.
E) They will change continually because of reversibility.

Question 10

Write the equilibrium expression for the following reaction, assuming homogeneity:
Fool(money)₁₀ $\leftrightarrows$ Fool + 10 money

A) $\left. K = [ \text { fool (money) } ) _ { 10 } \right] [ \text { fool } ] [ \text { money } ]$
B) $K = \frac { [ \text { fool } ] [ \text { money } ] ^ { 10 } } { \left[ \text { fool } ( \text { money } ) _ { 10 } \right] }$
C) $K = \left[ \text { fool } ( \text { money } ) _ { 10 } \right] [ \text { fool } ] [ \text { money } ] ^ { 10 }$
D) $K = \frac { \left[ \text { fool } ( \text { money } ) _ { 10 } \right] ^ { 10 } } { [ \text { fool] [money] } }$
E) $K = [ \text { fool } ] + 10 [ \text { money } ] - \left[ \text { fool } ( \text { money } ) _ { 10 } \right]$

Question 11

In a reversible reaction A $\leftrightarrows$ B at a particular temperature, the rate constant for the reverse reaction is twice the rate constant for the forward reaction. At equilibrium, how are the concentrations of A and B related?

A) Can't tell, need more information.
B) [A] = [B]
C) [A] = 2 *[B]
D) [A] = $\frac { 1 } { 2 } \times$
[B]
E) [A] = 4 *[B]

Question 12

Consider the equilibrium A + B $\leftrightarrows$ C. What is significant about the equilibrium state in which [B] = [C]?

A) [A] = K
B) [A] = [B] = [C]
C) [B] = [C] = K
D) [A] = 1/K
E) [C]/[B] = K

Question 13

A chemical equilibrium may be established by starting a reaction with ________

A) reactants only.
B) products only.
C) equal quantities of reactants and products.
D) any quantities of reactants and products.
E) All of the above.

Question 14

Which of A-D is equal in an equilibrium? If all are equal, answer E.

A) the concentrations of reactants and products
B) the rate constants for the forward and reverse reactions
C) the time that a particular atom or molecule spends as a reactant and product
D) the rate of the forward and reverse reaction
E) All of the above are equal.

Question 15

Which statement about a chemical reaction is not correct?

A) All chemical reactions are reversible since products can be converted back into the reactants.
B) If a reaction is characterized as lying far to the left, then the concentration of products is small when equilibrium is reached.
C) At equilibrium, the rates of the forward reaction and reverse reaction are equal.
D) At equilibrium, the rates of the forward and reverse reactions are equal because both have stopped.
E) Chemical equilibrium is said to be "a dynamic process."

Question 16

Which of the following is true for a chemical reaction at equilibrium?

A) only the forward reaction stops
B) only the reverse reaction stops
C) both the forward and reverse reactions stop
D) the rate constants for the forward and reverse reactions are equal
E) the rates of the forward and reverse reactions are equal

Question 17

A chemical equilibrium
2 A $\leftrightarrows$ B
Has a forward rate constant, k_f = 10 M ^-1 s^-1, and a reverse rate constant, k_r = 5 s^-1. If the system has a concentration of [A] = 0.10 M at equilibrium, what must be the concentration of B at equilibrium?

A) 20.0
B) 2.0
C) 0.20
D) 0.020
E) 200

Question 18

The law of mass action is a result of ________

A) the law of conservation of matter.
B) the law of conservation of energy.
C) kinetics of reversible reactions.
D) limiting reactant stoichiometry.
E) the third law of thermodynamics.

Question 19

In a reversible reaction A $\leftrightarrows$ B at a particular temperature, the rate constant for the reverse reaction is 4 times the rate constant for the forward reaction. What is the value of the equilibrium constant at that temperature?

A) Can't tell, need more information.
B) 0.25
C) 4
D) 16
E) 0.5

Question 20

Which of the following can be predicted from the law of mass action?
I. At equilibrium, the ratio of concentrations of products to reactants, each raised to a power corresponding to the stoichiometric coefficient in the balanced reaction equation, will have a constant value at a given temperature.
II. The direction of the reaction given values for the reactant and product concentrations and the equilibrium constant.
III. The rate at which reactants will be turned into products.

A) I only
B) II only
C) III only
D) I and II
E) I and III

Question 21

The equilibrium constant for the acid ionization of mercaptoethanol (HSCH₂CH₂OH ) is 1.91 *10^-10_.
HSCH₂CH₂OH(aq) $\leftrightarrows$
H⁺(aq) + SCH₂CH₂OH^-(aq)
Which of the following is true regarding this equilibrium?
I.The reaction is product-favored.
II.The reaction is reactant-favored.
III.Equilibrium lies far to the right.
IV.Equilibrium lies far to the left.

A) I and III
B) I and IV
C) II and III
D) II and IV
E) None are true, as the concentrations of reactants and products are comparable.

Question 22

Equilibrium constants can be expressed in terms of molar concentration, K_c, or partial pressure, K_P. To relate these two equilibrium constants to each other, ________

A) each concentration must be multiplied by the factor RT.
B) each pressure must be multiplied by the factor RT.
C) K_c must be multiplied by the factor RT.
D) K_P must be multiplied by the factor RT.
E) nothing must be done because their values are equal.

Question 23

For the following hypothetical equilibrium, what is the value of the equilibrium constant if the concentrations at equilibrium are as shown?
A + 2 B $\leftrightarrows$ C
[A] = 4.5 *10^-5 M
[B] = 2.2 *10^-2 M
[C] = 9.4*10^-3 M

A) 0.22
B) 9.9
C) 4.3 *10⁵
D) 2.3* 10⁸
E) 9.5 * 10³

Question 24

Under what conditions are the values of K_c and K_p for a given gas-phase equilibrium the same?

A) there is no change in the moles of gas in the reaction
B) there is no change in the temperature during the reaction
C) if the coefficients of the reactants and products are the same
D) if the pressure remains constant
E) if either K_c or K_p = 1

Question 25

Which statement about an equilibrium constant, K, and a reaction quotient, Q, for a reaction is correct?

A) Values for each can be determined using units of moles/liter or atmospheres.
B) K is the reciprocal of Q: K = 1/Q.
C) K always is larger than Q.
D) Q always is larger than K.
E) Q can never equal K.

Question 26

Water can decompose at an elevated temperature to give hydrogen and oxygen according to the equation below. At a particular temperature, the partial pressures of H₂O, H₂, and O₂ are 0.055 atm, 0.0065 atm, and 0.0045 atm, respectively, at equilibrium. What is the value of the equilibrium constant, K_P, for this reaction at this temperature?
2H₂O(g) $\leftrightarrows$ 2H₂(g) + O₂(g)

A) 5.3 *10^-4
B) 3.5 *10^-6
C) 6.3*10^-5
D) 1.6 *10⁴
E) 3.0 *10⁴

Question 27

For the chemical equilibrium aA + bB $\leftrightarrows$ cC, the value of the equilibrium constant, K, is 10. What is the value of the equilibrium constant for the following reaction?
2cC $\leftrightarrows$
2aA + 2bB

A) 0.10
B) 0.20
C) 0.010
D) 20
E) 10

Question 28

For the chemical equilibrium aA + bB $\leftrightarrows$ cC, the value of the equilibrium constant, K, is 10. What is the value of the equilibrium constant for the following reaction?
2aA + 2 bB $\leftrightarrows$ 2cC

A) 10
B) 20
C) 40
D) 100
E) 400

Question 29

For the chemical equilibrium aA + bB $\leftrightarrows$ cC, the value of the equilibrium constant, K, is 10. What is the value of the equilibrium constant for the following reaction?
CC $\leftrightarrows$ AA + bB

A) 0.10
B) 10
C) 1
D) 100
E) -10

Question 30

The equilibrium constant for the formation of hydrogen iodide from hydrogen and iodine is 45.0 at a certain temperature.
H₂(g) + I₂(s) $\leftrightarrows$ 2 HI(g)
Which of the following is true regarding this equilibrium?
I.The reaction is product-favored.
II.The reaction is reactant-favored.
III.Equilibrium lies to the right.
IV.Equilibrium lies to the left.

A) I and III
B) I and IV
C) II and III
D) II and IV
E) None are true, as the concentrations of reactants and products are essentially the same.

Question 31

An equilibrium that strongly favors products has ________

A) a value of K << 1.
B) a value of K >> 1.
C) a value of Q >> 1.
D) a value of Q << 1.
E) K = Q.

Question 32

The equilibrium constant for the formation of calcium carbonate from the ions in solution is
2.2 * 10⁸ according to the reaction:
Ca²⁺(aq) + CO₃^2-(aq) $\leftrightarrows$
CaCO₃(s)
What is the value of the equilibrium constant for the reverse of this reaction?

A) the same, 2.2 *10⁸
B) -2.2 * 10⁸
C) 2.2 *10^-8
D) 4.5 * 10^-9
E) 4.5 * 10⁹

Question 33

Gaseous carbon monoxide and hydrogen gas can be used to prepare methanol (CH₃OH). Under equilibrium conditions, the partial pressures of the components are $P _ { \mathrm { Co } }$ = 1.50 atm, $P _ { \mathrm { H } _ { 2 } }$
= 1)50 atm, $P _ { \mathrm { CH } _ { 3 } \mathrm { OH } }$
= 4)60 atm.
What is the value of the equilibrium constant, K_p, for the reaction in which 10 mol of methanol is produced?

A) 10.0
B) 1.36
C) 13.6
D) 2.46
E) 24.6

Question 34

The equilibrium constants for the two reactions are known: $\begin{array}{ll}\mathrm{M}^{\mathrm{m}+}+4 \mathrm{~L}^{-} \leftrightarrows\left[\mathrm{ML}_{4}\right]^{\mathrm{m}-4}&&&K_{a}\\\mathrm{HL} \leftrightarrows \mathrm{H}^{+}+\mathrm{L}^{-}&&&K_{b}\\\end{array}$ What must be the value of the equilibrium constant, K_overall for the following overall reaction?
M^m+ + 4HL $\leftrightarrows$ [ML₄]^m-4 + 4H⁺ K_overall

A) K_aK_b
B) K_a + 4K_b
C) K_a + K_b⁴
D) K_aK_b⁴
E) K_aK_b^1/4

Question 35

For the chemical equilibrium aA +bB $\leftrightarrows$ cC, the value of the equilibrium constant, K, is 10. What is the value of the equilibrium constant for the following reaction?


$\frac { 1 } { 2 }$ CC $\leftrightarrows$ $\frac { 1 } { 2 }$ AA+ $\frac { 1 } { 2 }$ BB

A) 0.32
B) 10
C) 3.2
D) 3.1
E) 32

Question 36

Write the expression for the reaction quotient for the reaction
Zn²⁺(aq) + 2NH₃(aq) $\leftrightarrows$ Zn(NH₃)²⁺(aq)

A) $Q = \left[ \mathrm { Zn } ^ { 2 + } \right] + 2 \left[ \mathrm { NH } _ { 3 } \right] + \left[ \mathrm { Zn } \left( \mathrm { NH } _ { 3 } \right) ^ { 2 + } \right]$
B) $Q = \frac { \left[ \mathrm { Zn } ^ { 2 + } \right] + 2 \left[ \mathrm { NH } _ { 3 } \right] } { \left[ \mathrm { Zn } \left( \mathrm { NH } _ { 3 } \right) ^ { 2 + } \right] }$
C) $Q = \frac { \left[ \mathrm { Zn } ^ { 2 + } \right] \left[ \mathrm { NH } _ { 3 } \right] ^ { 2 } } { \left[ \mathrm { Zn } \left( \mathrm { NH } _ { 3 } \right) ^ { 2 + } \right] }$
D) $Q = \frac { \left[ \mathrm { Zn } \left( \mathrm { NH } _ { 3 } \right) ^ { 2 + } \right] } { \left[ \mathrm { Zn } ^ { 2 + } \right] \left[ \mathrm { NH } _ { 3 } \right] ^ { 2 } }$
E) $Q = \left[ \mathrm { Zn } \left( \mathrm { NH } _ { 3 } \right) ^ { 2 + } \right] - \left[ \mathrm { Zn } ^ { 2 + } \right] - 2 \left[ \mathrm { NH } _ { 3 } \right]$

Question 37

Two students measured an equilibrium constant for the same chemical reaction. Ken obtained a value of 130 for the equilibrium constant, but Barbie obtained a value of 11.4. The instructor checked their results and said they were both correct. How can that be?

A) The values vary according to the way the measurement is made. Ken must have measured product concentrations, while Barbie measured reactant concentrations.
B) The values vary according to the starting conditions of the reaction prior to equilibrium. Ken must have started with all reactants, while Barbie must have started with all products.
C) The values vary according to the stoichiometric coefficients that are used. The balancing coefficients that Ken used must have been twice those that Barbie used.
D) The values vary according to direction of the reaction. Ken must have used the reverse reaction.
E) The instructor must have made a mistake, because the equilibrium constant for a reaction must always be the same.

Question 38

An increase in the number of moles of gas as the reaction goes from reactants to products in a gas-phase equilibrium results in ________

A) K_p > K_c.
B) K_p < K_c.
C) K_p = K_c.
D) K_p + K_c = (RT) ^{$\Delta$ n}.
E) K_pK_c = (RT) ^{$\Delta$ n}

Question 39

Coal (C) can be heated with steam (H₂O) at high temperatures to produce a mixture of hydrogen and carbon monoxide gases. Methanol, which is a useful fuel, can be produced from these gases by the reaction below. At a particular high temperature, the equilibrium concentrations are the following:
[H₂] = 0.095 mol/L, [CO] = 0.035 mol/L, [CH₃OH] = 0.065 mol/L. What is the value of the equilibrium constant, K_c, for this reaction at this temperature?
2H₂(g) + CO(g) $\leftrightarrows$ CH₃OH(g)

A) 4.70
B) 290
C) 206
D) 19.5
E) 4.86

Question 40

Equilibrium constants for gases can be expressed in terms of concentrations, K_c, or in terms of partial pressures, K_p. Which one of the following statements regarding K_c and K_p is correct?

A) K_c and K_p are equal when all stoichiometric coefficients in the balanced reaction equation equal one.
B) K_c and K_p have the same values but different units.
C) K_c and K_p are equal when the sum of the stoichiometric coefficients for the products equals the sum of the stoichiometric coefficients for the reactants.
D) K_c and K_p can never be equal.
E) K_c and K_p are equal when the conditions are standard (P = 1 atm, T = 298 K).

Question 41

For a chemical reaction at equilibrium, which of the following will change the value of the
Equilibrium constant K?
I.Changing the temperature
II.Changing the total concentration of reactants and products
III.Changing the reaction coefficients

A) I only
B) II only
C) III only
D) I and II only
E) I and III only

Question 42

Water can decompose at an elevated temperature to give hydrogen and oxygen according to the equation below. At a particular temperature in a vessel containing water vapor and air, the partial pressures of H₂O, H₂, and O₂ are 0.055 atm, 0.0065 atm, and 0.19 atm, respectively. What is the value of the reaction quotient, Q_P, for this reaction under these conditions?
2H₂O(g) $\leftrightarrows$ 2H₂(g) + O₂(g)

A) 0.023
B) 1.5 *10^-4
C) 2.7 *10^-3
D) 370
E) 4.4 * 10⁴

Question 43

Which of the following occurs when products are removed from a chemical reaction in solution or the gas phase at equilibrium?

A) Q increases and the equilibrium shifts to produce more products.
B) Q increases and the equilibrium shifts to produce more reactants.
C) Q decreases and the equilibrium shifts to produce more products.
D) Q decreases and the equilibrium shifts to produce more reactants.
E) Q is unchanged by the removal of products.

Question 44

In equilibrium expressions, the concentrations of pure solids and liquids ________

A) have the assigned value of one.
B) have the assigned value of zero.
C) have constant values, c_S and c_l.
D) are determined from the density and molar mass.
E) are treated as any other solute.

Question 45

Consider the equilibrium A + B $\leftrightarrows$ C. What is significant about the reaction quotient when [B] = [C]?

A) only that [B] = [C]
B) [A] = [B] = [C]
C) [B] = [C] = K
D) [A] = K
E) The reaction must run in the forward direction.

Question 46

Dry ice (solid carbon dioxide) is placed in a sealed container. It sublimes to produce carbon dioxide gas and reaches equilibrium at a given temperature. If the amount of dry ice in the container is doubled, then ________.
CO₂(s) $\leftrightarrows$ CO₂(g)

A) the amount of CO₂(g) would double.
B) the amount of CO₂(g) would increase but not double.
C) the partial pressure of CO₂(g) would increase.
D) the amount of CO₂(g) would not change.
E) the equilibrium amount of CO₂(s) would be less.

Question 47

In a simple equilibrium A + B $\leftrightarrows$ C, will there be any stress to the system if both B and C are added to the equilibrium system simultaneously and in the same amount?

A) No, these two stresses will always cancel each other out.
B) No, these two stresses will cancel each other out unless the initial concentrations of B and C are also the same.
C) Yes, the same amount of A is also required for the stresses to cancel each other out.
D) Yes, unless the initial concentrations of B and C are also the same.
E) More than two of the above statements are correct.

Question 48

Solid mercury(II) oxide decomposes when heated to produce liquid mercury and oxygen.
2HgO(s) $\leftrightarrows$ 2Hg(l) + O₂(g)
An amount of mercury(II) oxide is placed in a vessel at a particular temperature and allowed to reach equilibrium. How could the amount of liquid mercury in the vessel be increased?
I. Adding more mercury(II) oxide.
II. Removing some oxygen.
III. Increasing the volume of the vessel.

A) I only
B) II only
C) III only
D) I and II
E) II and III

Question 49

Which one of the following is the equilibrium expression, K_P, for the reaction that produces lime, CaO, from limestone, CaCO₃? CaCO₃(s) $\leftrightarrows$
CaO(s) + CO₂(g)

A) $\frac { \left[ \mathrm { CaCO } _ { 3 } \right] } { [ \mathrm { CaO } ] \left[ \mathrm { CO } _ { 2 } \right] }$
B) $\frac { 1 } { \mathrm { P } _ { \mathrm { Co } _ { 2 } } }$
C) $\frac { [ \mathrm { CaO } ] \left[ \mathrm { CO } _ { 2 } \right] } { \left[ \mathrm { CaCO } _ { 3 } \right] }$
D) [CaO][CO₂]
E) $\mathrm { P } _ { \mathrm { co } _ { 2 } }$

Question 50

If the reaction quotient Q has a larger value than the related equilibrium constant, K, ________

A) the reaction is at equilibrium.
B) the reaction will continue to make more products.
C) the reaction will consume products and make reactants.
D) the reaction will release heat to achieve equilibrium.
E) the value of K will increase until it is equal to Q.

Question 51

If the reaction quotient Q has a smaller value than the related equilibrium constant, K, ________

A) the reaction is at equilibrium.
B) the reaction will continue to make more products.
C) the reaction will consume products and make reactants.
D) the reaction will release heat to achieve equilibrium.
E) the value of K will decrease until it is equal to Q.

Question 52

The water gas shift reaction shown below can be used to produce hydrogen from water and coal. Given the data in the following table, which experiment will proceed in the forward direction to produce more hydrogen? Under the experimental conditions, K_c = 25 for this reaction.
H₂O(g) + CO(g) $\leftrightarrows$ H₂(g) + CO₂(g)
Initial Concentrations (mol/L) $$\begin{array} { | c | c | c | c | c | } \hline \text { Experiment } & { \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] } & { [ \mathrm { CO } ] } & { \left[ \mathrm { H } _ { 2 } \right] } & { \left[ \mathrm { CO } _ { 2 } \right] } \\\hline \text { I } & 0.030 & 0.030 & 0 & 0 \\\hline \text { II } & 0 & 0 & 0.030 & 0.030 \\\hline \text { III } & 0.020 & 0.020 & 0.050 & 0.040 \\\hline \text { IV } & 0.030 & 0.020 & 0.030 & 0.020 \\\hline\end{array}$$

A) I only
B) II only
C) I and III
D) I, III, and IV
E) I and IV

Question 53

What happens to the equilibrium between NO₂(g) and N₂O₄(g) in inert argon when the volume is increased and additional argon is added to maintain a constant total pressure?

A) The ratio of NO₂ to N₂O₄ increases solely because of the increase in volume.
B) The ratio of NO₂ to N₂O₄ increases solely because of the addition of argon.
C) The ratio of NO₂ to N₂O₄ decreases solely because of the increase in volume.
D) The ratio of NO₂ to N₂O₄ decreases solely because of the addition of argon.
E) The ratio of NO₂ to N₂O₄ remains the same, because the effects of the two processes cancel each other out.

Question 54

Which of the following is the equilibrium expression for the scrubbing reaction of calcium oxide and sulfur dioxide to remove sulfur dioxide from the exhaust gases of coal-fired power plants?
CaO(s) + SO₂(g) $\leftrightarrows$ CaSO₃(s)

A) K_c = [SO₂]
B) $K _ { c } = \frac { 1 } { \left[ \mathrm { SO } _ { 2 } \right] }$
C) K_c = [CaO] + [SO₂]
D) $K _ { \mathrm { c } } = \frac { \left[ \mathrm { CaSO } _ { 3 } \right] } { \left[ \mathrm { SO } _ { 2 } \right] [ \mathrm { CaO } ] }$
E) K_c = [CaSO₃] - [CaO] - [SO₂]

Question 55

Which of the following occurs when reactants are added to a chemical reaction in solution or the gas phase at equilibrium?

A) Q increases and the equilibrium shifts to produce more products.
B) Q increases and the equilibrium shifts to produce more reactants.
C) Q decreases and the equilibrium shifts to produce more products.
D) Q decreases and the equilibrium shifts to produce more reactants.
E) Q is unchanged by the addition of reactants.

Question 56

Addition of reactants to a chemical reaction in solution or gas phase at equilibrium results in ________

A) an increase in K and a shift in equilibrium to produce more products.
B) an increase in K and a shift in equilibrium to produce more reactants.
C) a decrease in K and a shift in equilibrium to produce more products.
D) a decrease in K and a shift in equilibrium to produce more reactants.
E) no change in K and a shift in equilibrium to produce more products.

Question 57

Lime is obtained ________

A) by heating calcium sulfite at 900 $\degree$ C.
B) as a by-product of burning coal.
C) from the reaction between calcium oxide and sulfur dioxide.
D) by heating calcium carbonate at 900 $\degree$ C.
E) from sweet soil.

Question 58

Sulfur dioxide emitted in the burning of coal is "scrubbed" from the effluent using ________

A) limestone (CaCO₃).
B) lime (CaO).
C) calcium metal (Ca).
D) calcium hydride (CaH₂).
E) calcium hydroxide [Ca(OH)₂].

Question 59

Gaseous carbon monoxide and hydrogen gas can be used to prepare methanol (CH₃OH). Calculate a value for the reaction quotient when the partial pressures are $P _ { \mathrm { Co } }$ = 15.0 atm, $P _ { \mathrm { H } _ { 2 } }$
= 15.0 atm, $P _ { \mathrm { CH } _ { 3 } \mathrm { OH } }$ = 1.00 atm.

A) 1.00
B) 2.96* 10^-4
C) 6.67*10^-2
D) 4.44 *10^-3
E) 3.33*10^-2

Question 60

Identify whether or not perturbations A through D will affect the equilibrium concentrations of reactants and products in a gas-phase endothermic chemical reaction that involves one or more gases. If all have an effect on the equilibrium concentrations, select response E. Otherwise, identify the one that does not affect the equilibrium concentrations.

A) adding reactants to a gas or solution reaction
B) removing products from a gas or solution reaction
C) decreasing the temperature
D) increasing pressure by adding an inert gas to a reaction in the gas phase
E) All of the above are perturbations to chemical equilibrium.

Question 61

Gaseous carbon monoxide and hydrogen gas can be used to prepare methanol (CH₃OH). Under equilibrium conditions at 427°C, the partial pressures of the components are as follows.
P_CO = 1.44 atm $P _ { \mathrm { H } _ { 2 } }$
= 4.25 atm $P _ { \mathrm { CH } _ { 3 } \mathrm { OH } }$
= 2.30 atm
What is the value of the equilibrium constant for the reaction in which one mole of methanol is produced?

Question 62

A reaction is run under conditions in which the equilibrium constant is known to be 2.5. *10². At equilibrium, the forward rate is determined to be 5.0 *10^-4 mol L^-1 s^-1. What is the rate of the reverse reaction under these conditions?

Question 63

The gas-phase equilibrium of the oxidation of sulfur dioxide, shown here, has an equilibrium constant, K_p, value of 4.17 * 10² at 200 $\degree$ C. If a closed vessel was filled with sulfur trioxide and the initial pressure of SO₃ was 0.033 atm at 200 $\degree$ C, what would be the final partial pressure of SO₃?
2SO₂(g) + O₂(g) $\leftrightarrows$ 2SO₃(g)

A) more than 0.033 atm
B) less than 0.033 atm
C) 0.033 atm exactly
D) there is no way to tell

Question 64

The reaction of bromine gas with chlorine gas, shown here, has a K_p value of 7.20. If a closed vessel was charged with the two reactants, each at an initial partial pressure of 0.500 atm, and the product also at 0.500 atm, what would be the equilibrium partial pressure of BrCl(g)?
Br₂(g) + Cl₂(g) $\leftrightarrows$ 2BrCl(g)

A) 0.500 atm
B) 0.680 atm
C) 0.859 atm
D) 0.029 atm
E) 0.987 atm

Question 65

Hydrofluoric acid is used in the preparation of numerous pharmaceuticals (e.g., Prozac) and industrial materials (e.g., Teflon). It can be produced by the reaction of hydrogen and fluorine gases. Starting with initial concentrations of 2.00 M for H₂ and 2.00 M for F₂, what would be the equilibrium concentration of HF? The equilibrium constant for the reaction K_c = 115.

A) 0.85 M
B) 1.69 M
C) 2.85 M
D) 3.37 M
E) 4.00 M

Question 66

Increasing the temperature of an exothermic reaction results in ________

A) more products and fewer reactants.
B) more reactants and fewer products.
C) more reactants and products.
D) fewer reactants and products.
E) no change in the quantities of reactants and products.

Question 67

When can an x be ignored in solving an equilibrium expression derived from a RICE table?

A) whenever it simplifies the calculation
B) whenever it is very much smaller than the term it is added to or subtracted from
C) whenever the equilibrium concentration for that species is relatively very small
D) whenever it is raised to any power higher than 1
E) never

Question 68

A student determined the equilibrium concentration in the following equation by neglecting the x term in the denominator. Was she justified or not in this approximation and why?
K = 4.0 *10^-2 = $\frac { x ^ { 2 } } { ( 0.05 - x ) }$

A) Yes, the concentration is much greater than K, so the x can be ignored.
B) Yes, the value of x determined in this way is less than 0.05, so it can be ignored.
C) No, the value of x determined in this way significantly reduces the denominator.
D) No, the value of x can never be ignored in solving an algebra problem.
E) No, the value of K is much less than 1, so x cannot be ignored.

Question 69

The sulfide ion, S^2-, reacts with water as a weak base:
S^2- + H₂O $\leftrightarrows$ SH^- + OH^- K = 1.0
If sodium sulfide were dissolved in water to make a solution of 0.50 M, what would be the resulting concentration of OH^-?

A) 0.50 M
B) 0.37 M
C) 0.63 M
D) 1.0 M
E) 0.19 M

Question 70

Write an expression for the equilibrium constant for the formation of two moles of ammonia gas (NH₃) from nitrogen and hydrogen in their standard states.

Question 71

Carbon dioxide and argon, which is a noble or inert gas, are placed in a vessel and heated. Equilibrium is reached at some particular temperature. Carbon dioxide dissociates by the following reaction.
2CO₂(g) $\leftrightarrows$ 2CO(g) + O₂(g)
What is the result of increasing the pressure by adding more argon?
I. The equilibrium shifts to produce more carbon dioxide and reduce the pressure.
II. The equilibrium shifts to remove carbon dioxide and reduce the pressure.
III. The equilibrium does not change because argon is not involved in the reaction.
IV. The equilibrium does not change because the concentrations are not affected.

A) I only
B) II only
C) III only
D) IV only
E) III and IV

Question 72

A 10.0 L flask at 500 K is filled with 0.30 mol of hydrogen and 0.30 mol of iodine. They react as indicated below. The equilibrium constant K_c = 45.0. What are the equilibrium concentrations of the three gases?
H₂(g) + I₂(g) $\leftrightarrows$ 2HI(g)

A) [H₂] = [I₂] = 0.023 M, [HI] = 0.046 M
B) [H₂] = [I₂] = 0.0069 M, [HI] = 0.046 M
C) [H₂] = [I₂] = [HI] = 0.023 M
D) [H₂] = [I₂] = 0.0069 M, [HI] = 0.023 M
E) [H₂] = [I₂] = 0.23 M, [HI] = 0.46 M

Question 73

Chemical equilibrium arises from the ________ of chemical reactions and is reached when the ________ of the forward reaction is equal to the ________ of the reverse reaction.

Question 74

The reaction of bromine gas with chlorine gas, shown here, has a K_p value of 7.20. If a closed vessel was charged with the two reactants, each at an initial partial pressure of 0.500 atm, what would be the equilibrium partial pressure of BrCl(g)?
Br₂(g) + Cl₂(g) $\leftrightarrows$ 2BrCl(g)

A) 1.9 atm
B) 1.4 atm
C) 0.84 atm
D) 0.29 atm
E) 0.57 atm

Question 75

Which of the following is true regarding the effect of a catalyst on chemical equilibrium?

A) Only the forward rate increases, so the quantity of products increases.
B) Only the forward rate increases, but the quantity of products remains the same.
C) Both the forward and reverse rates increase, and the quantity of products increases.
D) Both the forward and reverse rates increase, but the quantity of products is unchanged.
E) The effect varies depending on whether the reaction is endothermic or exothermic.

Question 76

Cylinders of NO gas may contain small quantities of oxygen as an impurity, leading to the formation of NO₂ in equilibrium with the NO and the oxygen. Is this contamination by NO₂ dependent on the pressure in the tank?

A) Yes, there will be more NO₂ at higher pressures.
B) Yes, there will be less NO₂ at higher pressures.
C) No, the amount of NO₂ has nothing to do with pressure.
D) No, the amount of NO₂ depends on the partial pressure, not the total pressure.
E) There is no way to tell without additional information.

Question 77

In the Reaction, Initial, Change, Equilibrium (RICE) table started for calculating equilibrium concentrations of the reaction shown, the terms in the "change" row are ________
M²⁺ + 4L $\leftrightarrows$ ML₄²⁺ $$\begin{array} { l l c c c } \mathbf { R } & { \left[ \mathbf { M } ^ { 2 + } \right] } & { [ \mathbf { L } ] } & { \left[ \mathbf { M L } _ { 4 ^ { 2 + } } \right] } \\\text { I } & 0.10 M & 0.32 M & 0 M \\\text { C } & & & \\\text { E } & & &\end{array}$$

A) -x, -x, +x.
B) +x, +x, -x.
C) -x, -4x, +x.
D) +x, +4x, +x.
E) +x, +4x, -x.

Question 78

To solve an equation of the form ax² + bx + c = 0 for values of x, use ________

A) $x = \left\{ \frac { b + c } { a } \right\} \frac { 1 } { 2 }$
B) $a x ( x + b ) = - c$
C) $x = \frac { \left\{ - b \pm \left( b ^ { 2 } - 4 a c \right) \right\} } { 2 a }$
D) $x = \frac { \left\{ - b \pm \left( b ^ { 2 } - 4 a c \right) ^ { 1 / 2 } \right\} } { 2 a }$
E) $x = \frac { \left\{ - b \pm \left( b ^ { 2 } - 4 a c \right) \right\} ^ { 1 / 2 } } { 2 a }$

Question 79

If the temperature of an endothermic reaction at equilibrium could be increased instantaneously, what would be the instantaneous effect on Q and K before equilibrium was again achieved?

A) Q would increase and K would stay the same.
B) Q would decrease and K would stay the same.
C) Q would stay the same and K would increase.
D) Q would stay the same and K would decrease.
E) Both Q and K would stay the same.

Question 80

A reaction X + 2Y $\rightarrow$ 3Z is started with 1.0 M Z and no X or Y. To calculate the equilibrium concentrations of all species using a RICE table, which of the following would you enter in the
Z column for the C row?

A) 1.0 M
B) 1.0 M - x
C) 1.0 M - 3x
D) 1.0 M + 3x
E) -3x