Deck 14: Chemical Equilibrium

Question 1

For which of the following values of an equilibrium constant (K_eq)would you expect the equilibrium to lie farthest to the right (product most highly favored)?

A)0.491, at 20 °C
B)1.04, at 20 °C
C)10.6, at 20 °C
D)1.46 × 10^-4 at 20 °C

Answer 1

10.6, at 20 °C

Question 2

When a reaction shows one arrow pointing from left to right, this means ________.

A)the reaction has reached equilibrium
B)the reaction favors the right direction
C)there is practically no reactant left
D)both B and C

Answer 2

the reaction favors the right direction

Question 3

Given this reaction at equilibrium: N₂O₄ (g)⇔ 2NO₂ (g)
Calculate the equilibrium constant (K_eq)if the concentrations of N₂O₄ and NO₂ are 0.0238 M and
0.196 M, respectively.

A)8.34
B)346
C)0.621
D)1.61

Answer 3

1.61

Question 4

Which of the following statements about the equilibrium constant is incorrect?

A)If K_eq > 1 the reaction favors product formation.
B)If K_eq > 1 the reaction does not favor product formation.
C)If K_eq = 1 the reaction is at equilibrium.
D)If K_eq < 1 the reaction does not favor product formation.

Question 5

Consider the equation 2SO₂ (g)+ O₂ (g)⇔ 2SO₃ (g). Increasing the pressure will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 6

Which statement is true about equilibrium?

A)The forward reaction rate is greater than the reverse reaction rate.
B)The reverse reaction rate is greater than the forward reaction rate.
C)The forward reaction rate is equal to the reverse reaction rate.
D)Either A or B depending on the reaction.

Question 7

The equilibrium constant expression for the reaction 2SO₃ (g)+ 2Cl₂ (g)⇔ 2SO₂Cl₂ (g)+ O₂ (g)is ________.

A)K_eq = [SO₂Cl₂] × [O₂] / [SO₃] × [Cl₂]
B)K_eq = [SO₃] × [Cl₂] / [SO₂Cl₂] × [O₂]
C)K_eq = [SO₂Cl₂]² × [O₂] / [SO₃]² × [Cl₂]²
D)K_eq = [SO₃]² × [Cl₂]² / [SO₂Cl₂]² × [O₂]

Question 8

Which of the following statements is true for a chemical reaction (in progress)that has not reached an equilibrium position?

A)The "reverse" reaction rate is zero.
B)The "forward" reaction rate is zero.
C)The "forward" and "reverse" reaction rates are equal.
D)Both A and B are true statements.
E)None of the above are true statements.

Question 9

Which of the following statements best describes the rate of the "forward" (i.e., left-to-right)reaction as it approaches equilibrium?

A)The rate increases as equilibrium is approached.
B)The rate decreases as equilibrium is approached.
C)The rate remains constant.
D)The rate slows down, then increases, as equilibrium is approached.

Question 10

The equilibrium concentrations for the reaction Cl₂ (g)+ PCl₃ (g)⇔ PCl₅ (g)at 300 K are [Cl₂] = 0.75 M, [PCl₃] = 0.45 M, and [PCl₅] = 0.73 M. Based on the calculated value of the equilibrium constant, the reaction is ________.

A)favorable
B)unfavorable
C)temperature dependent
D)temperature independent

Question 11

For this chemical reaction (at equilibrium): N₂ (g)+ 3H₂ (g)⇔ 2NH₃ (g)
Which of the following statements is true of the reaction rate?

A)The forward rate (l to r)is faster than the reverse rate (r to l).
B)The reverse rate (r to l)is faster than the forward rate (l to r).
C)Both the forward and reverse rates are zero.
D)The forward and reverse rates are the same.

Question 12

Consider the equation 2SO₃ (g)+ 2Cl₂ (g)⇔ 2SO₂Cl₂ (g)+ O₂ (g). Decreasing the pressure will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 13

The equilibrium constant expression for the reaction N₂ (g)+ 3H₂ (g)⇔ 2NH₃ (g)is ________.

A)K_eq = [N₂] [3H₂]³ / [2NH₃]²
B)K_eq = [NH₃]² / [N₂] [H₂]³
C)K_eq = [N₂] [H₂]³ / [NH₃]²
D)K_eq = [2NH₃]² / [N₂] [3H₂]³

Question 14

The equilibrium constant is equal to which of the following?

A)k_forward / k_reverse
B)k_reverse / k_forward
C)k_forward × k_reverse
D)1 / (k_forward/k_reverse⁾

Question 15

If the value of the equilibrium constant for the reverse reaction is 2.5 × 10^-6, the value of the equilibrium constant for the forward reaction is ________.

A)-2.5 × 10^-6
B)4.0 × 10⁵
C)2.5 × 10⁶
D)4.0 × 10⁷

Question 16

Consider the reaction N₂O₄ (g)⇔ 2NO₂ (g)with Kc = 0.211. Which of the following pairs of concentrations indicate that the system is not at equilibrium?

A)[N₂O₄] = 0.00140 M; [NO₂] = 0.0172 M
B)[N₂O₄] = 0.00280 M; [NO₂] = 0.0243 M
C)[N₂O₄] = 0.00452 M; [NO₂] = 0.0310 M
D)[N₂O₄] = 0.00840 M; [NO₂] = 0.0572 M

Question 17

For the following reaction, the equilibrium constant (K_eq)is equal to 53.3. What is the concentration of I₂ at equilibrium, if the concentrations of HI and H₂ are 0.212 M and 1.576 M, respectively? H₂ + I₂ ⇔ 2HI

A)1.576 M
B)0.000535 M
C)0.212 M
D)0.314 M

Question 18

The equilibrium concentrations for the reaction N₂ (g)+ 3H₂ (g)⇔ 2NH₃ (g)at 673 K are [H₂] = 0.63 M, [N₂] = 0.45 M, and [NH₃] = 0.24 M. The value of K_eq is ________.

A)0.85
B)1.18
C)0.51
D)1.96

Question 19

For which of the following values of an equilibrium constant (K_eq)would you expect the equilibrium to lie farthest to the left (reactants most highly favored)?

A)0.491, at 20 °C
B)1.04, at 20 °C
C)10.6, at 20 °C
D)1.46 × 10^-4, at 20 °C

Question 20

Consider the equation 2SO₂ (g)+ O₂ (g)⇔ 2SO₃ (g). Adding more oxygen will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 21

Consider the equation 2SO₂ (g)+ O₂ (g)⇔ 2SO₃ (g). Removing product will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 22

Consider the reaction: 2H₂S (g)+ 3O₂ (g)⇔ 2SO₂ (g)+ 2H₂O (g)to answer the following questions.
Refer to the reaction shown above. Adding helium to the reaction vessel will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 23

Consider the reaction: FeCl₃ + KSCN ⇔ K₃[Fe(SCN)₆] + 3KCl
yellow colorless red colorless
Refer to the equilibrium shown above. Adding iron(III)chloride will ________.

A)turn the solution red.
B)turn the solution less red.
C)turn the solution clear.
D)have no effect on the color.

Question 24

In an endothermic reaction, adding heat will ________.

A)increase the amount of products
B)decrease the amount of reactants
C)decrease the amount of products
D)both A and B

Question 25

Consider the equation 2NH₃ (g)⇔ N₂ (g)+ 3H₂ (g). Increasing the volume will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 26

Consider the reaction: 2H₂S (g)+ 3O₂ (g)⇔ 2SO₂ (g)+ 2H₂O (g)to answer the following questions.
Refer to the reaction shown above. Removing sulfur dioxide as it is formed will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 27

In an exothermic reaction, adding heat will ________.

A)increase the amount of products
B)decrease the amount of reactants
C)decrease the amount of products
D)both A and B

Question 28

Consider the equation O₂ (g)+ 2H₂ (g)⇔ 2H₂O (g). Increasing the concentration of hydrogen gas will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 29

Consider the reaction: A + 3B ⇔ 2C. Equal numbers of moles for A and B are added to the reaction vessel and equilibrium established. At that point ________.

A)[A] < [B]
B)[A] > [B]
C)[A] = [B]
D)One cannot say unless the equilibrium constant value is known.

Question 30

Consider the equation 2NH₃ (g)⇔ N₂ (g)+ 3H₂ (g). Increasing the pressure will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 31

Consider the equation 2NH₃ (g)⇔ N₂ (g)+ 3H₂ (g). Decreasing the concentration of ammonia gas will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 32

For an endothermic reaction, lowering the temperature of the reaction will ________.

A)increase the amount of products
B)decrease the amount of reactants
C)decrease the amount of products
D)both A and B

Question 33

Consider the equation: CH₄ (g)+ 2O₂ (g)⇔ CO₂ (g)+ 2H₂O (g)to answer the questions below.
Refer to the equilibrium shown above. If oxygen is removed this will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 34

Consider the reaction: 2H₂S (g)+ 3O₂ (g)⇔ 2SO₂ (g)+ 2H₂O (g)to answer the following questions.
Refer to the reaction shown above. Increasing the volume of the system will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 35

Consider the equation: CH₄ (g)+ 2O₂ (g)⇔ CO₂ (g)+ 2H₂O (g)to answer the questions below.
Refer to the equilibrium shown above. If the reaction vessel is expanded, this will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 36

Consider the equation: CH₄ (g)+ 2O₂ (g)⇔ CO₂ (g)+ 2H₂O (g)to answer the questions below.
Refer to the equilibrium shown above. Adding excess oxygen will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is not known

Question 37

Consider the equation N₂ (g)+ 3H₂ (g)⇔ 2NH₃ (g). Removing ammonia as soon as it is formed will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 38

For an exothermic reaction, lowering the temperature of the reaction will ________.

A)increase the amount of products
B)decrease the amount of reactants
C)decrease the amount of products
D)both A and B

Question 39

Consider the reaction: 2H₂S (g)+ 3O₂ (g)⇔ 2SO₂ (g)+ 2H₂O (g)to answer the following questions.
Refer to the reaction shown above. Which of the following will shift the equilibrium to the left?

A)adding sulfur dioxide
B)adding hydrogen sulfide
C)decreasing the pressure
D)both A and C

Question 40

Consider the reaction: 2H₂S (g)+ 3O₂ (g)⇔ 2SO₂ (g)+ 2H₂O (g)to answer the following questions.
Refer to the reaction shown above. Adding H₂O to the reaction vessel will ________.

A)shift the reaction to the right
B)shift the reaction to the left
C)have no effect
D)cannot be determined, since the temperature is unknown

Question 41

Consider the reaction: FeCl₃ + KSCN ⇔ K₃[Fe(SCN)₆] + 3KCl
yellow colorless red colorless
Refer to the equilibrium shown above. Adding a catalyst will ________.

A)turn the solution red.
B)turn the solution less red.
C)turn the solution clear.
D)have no effect on the color.

Question 42

Consider the reaction: FeCl₃ + KSCN ⇔ K₃[Fe(SCN)₆] + 3KCl
yellow colorless red colorless
Refer to the equilibrium shown above. Adding a couple of drops of an aqueous KCl solution will ________.

A)turn the solution red.
B)turn the solution less red.
C)turn the solution clear.
D)have no effect on the color.

Question 43

Consider the reaction: FeCl₃ + KSCN ⇔ K₃[Fe(SCN)₆] + 3KCl
yellow colorless red colorless
Refer to the equilibrium shown above. Adding KSCN will ________.

A)turn the solution red.
B)turn the solution less red.
C)turn the solution clear.
D)have no effect on the color.

Question 44

If the solubility of calcium fluoride is 2.0 × 10^{-4 M}, the solubility product value is ________.

A)1.6 × 10^-12
B)3.2 × 10^-11
C)4.0 × 10^-8
D)8.0 × 10^-12

Question 45

If more reactants are added to a chemical reaction already at equilibrium (thus disturbing it),
a reactant-to-product shift is required to restore an equilibrium condition.

Question 46

An "equilibrium condition" can be achieved only when the reactant-to-product conversion is complete (100% of the reactants have been converted to products).

Question 47

At equilibrium, the "amount of product" present is always greater than the "amount of reactant" present.

Question 48

For the reaction N₂ (g)+ 2H₂ (g)⇔ N₂H₄ (g)(endothermic), what condition will increase the yield of product?

A)high temperature, high pressure
B)high temperature, low pressure
C)low temperature, high pressure
D)low temperature, low pressure

Question 49

At equilibrium, the rate of the "forward" reaction is equal to the rate of the "reverse" reaction.

Question 50

If the solubility of copper(II)sulfate is 4.9 × 10^-3 M, the solubility product is ________.

A)2.4 × 10^-5
B)9.6 × 10^-5
C)1.2 × 10^-2
D)8.7 × 10^-8

Question 51

An equilibrium condition can be approached when the rate of a "forward" reaction slows down and the rate of a "reverse" reaction speeds up.

Question 52

The solubility product expression for silver(I)sulfate is ________.

A)K_sp = [Ag⁺] × [SO₄^-2]
B)K_sp = [2 Ag⁺] × [SO₄^-2]
C)K_sp = [Ag⁺]² × [SO₄^-2]
D)K_sp = [2Ag⁺]² × [SO₄^-2]

Question 53

A reaction that favors products has a K_eq > 1.

Question 54

There is no reaction in which 100% of the reactants are consumed.

Question 55

An equilibrium state can also be approached when a rapid "reverse" reaction slows down and a slower "forward" reaction speeds up.

Question 56

At equilibrium, the concentrations of reactants and products are always exactly the same.

Question 57

The solubility of SrF₂ in water (given K_sp = 2.6 × 10^-9 )is ________.

A)4.3 × 10^{-4 M}
B)1.2 × 10^{-4 M}
C)7.6 × 10^{-5 M}
D)8.7 × 10^{-4 M}

Question 58

The concentrations of reactants and products do not change as equilibrium is approached only the rate at which products are formed and reactants are consumed.

Question 59

The "equilibrium condition" of a chemical reaction is in no way related to temperature.

Question 60

If the solubility product of tin(II)carbonate is 1.03 × 10^-9, the molar solubility is 3.21 × 10^-5 M.

Question 61

If you could somehow remove I₂ from the following reaction (already at equilibrium):
H₂ + I₂ ⇔ 2HI
what would you expect to happen to the rate of the reverse reaction (right to left)?

Question 62

In the reaction N₂ (g)+ O₂ (g)⇔ 2NO (g), reducing the pressure will shift the equilibrium to the right.

Question 63

In the reaction Ni (s)+ 4CO (g)⇔ Ni(CO)₄ (g), adding extra nickel will shift the equilibrium to the right.

Question 64

Among the two reactions whose equilibrium constants are 0.003 and 30, the one that will produce greater quantities of products is the one whose equilibrium constant is 30.

Question 65

Predict the shift in the direction of the reaction for the following chemical reaction:
CH₄ + O₂ ⇔ CO₂ + H₂O
a)if methane (CH₄)is added.
b)if carbon dioxide (CO₂)is added.
c)if water (H₂O)is removed.

Question 66

In the reaction N₂H₄ (g)⇔ 2 H₂ (g)+ N₂ (g)at 1500 K, the equilibrium concentrations of each species are, [N₂] = 0.10 M, and [N₂H₄] = 0.10 M. The equilibrium constant value is 0.04.

Question 67

In the reaction N₂ (g)+ 2O₂ (g)⇔ 2NO₂ (g), reducing the pressure will shift the equilibrium to the left

Question 68

The term "molar solubility of a salt" refers to the molar concentration of one anion (or cation)formed in an aqueous , saturated solution of that salt.

Question 69

If the value of the equilibrium constant for the forward reaction is 2.5 × 10³⁰, the value of the equilibrium constant for the reverse reaction is 4.0 × 10^-30.

Question 70

In the reaction Cl₂ (g)+ 3F₂ (g)⇔ 2ClF₃ (g), reducing the pressure will shift the equilibrium to the right.

Question 71

Predict the shift in the direction of the reaction for the following chemical reaction:
3O₂ + ultraviolet light ⇔ 2O₃
a)if oxygen (O₂)is added.
b)if ozone (O₃)is removed.
c)if oxygen (O₂)is removed.
d)if more ultraviolet light is added.

Question 72

In the reaction 3O₂ (g)⇔ 2O₃ (g), expanding the reaction vessel will shift the equilibrium to the right.

Question 73

The double arrow in a chemical reaction indicates that the equilibrium is established because the rate of the forward reaction is equal to the rate of the reverse reaction.

Question 74

Predict the shift in the direction of the reaction for the following chemical reaction:
4HCl + O₂ ⇔ 2Cl₂ + 2H₂O
a)if you add water (H₂O).
b)if you remove chlorine (Cl₂).
c)if you remove oxygen (O₂).

Question 75

If you could somehow add more N₂O₄ to the following reaction (already at equilibrium):
N₂O₄ ⇔ NO₂
what would expect to happen to the rate of the forward (left to right)reaction?

Question 76

A product favored reaction has K_eq < 1.

Question 77

In the reaction PCl₅ ⇔ PCl₃ + Cl₂ at 500 K, the equilibrium concentrations of each species are
[PCl₅] = 0.008 M, [PCl₃] = 0.02 M, and [Cl₂] = 0.02 M. The equilibrium constant value is 0.5.

Question 78

Adding a catalyst to any reaction will always change the value of the equilibrium constant.

Question 79

In the reaction 3O₂ (g)⇔ 2O₃ (g), removing ozone as soon as it is formed will shift the equilibrium to the right.

Question 80

Changing the temperature of a reaction will not change the equilibrium value.