Deck 14: Chemical Equilibrium

Question 1

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

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

Answer 1

0.51

Question 2

For which of the following values of an equilibrium constant, Keq, would you expect the equilibrium to lie farthest to the right?

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 2

10.6, at 20 °C

Question 3

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.

Answer 3

The forward reaction rate is equal to the reverse reaction rate.

Question 4

For the following reaction, the equilibrium constant, Keq, 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 5

For which of the following values of an equilibrium constant, Keq, would you expect the equilibrium to lie farthest to the left?

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 6

Calculate the equilibrium concentration of N₂ for the following reaction. + The equilibrium constant Keq is 0.055 and the concentrations of and are 1.20 M and 0.225 M, respectively.

A) 0.0915 M
B) 0.533 M
C) 0.915 M
D) 3.41 M

Question 7

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 is faster than the reverse rate.
B) The reverse rate is faster than the forward rate.
C) Both the forward and reverse rates are zero.
D) The forward and reverse rates are the same.

Question 8

The equilibrium concentrations for the reaction 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 ________. CL₂ (g) + PCL₃ (g) PCl₅ (g)

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

Question 9

The equilibrium constant is equal to which of the following?

A) kforward / kreverse
B) kreverse / kforward
C) kforward × kreverse
D) 1 / (kforward/kreverse)

Question 10

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

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

Question 11

Which of the following statements is true for a chemical reaction that has not reached an equilibrium?

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 12

Increasing the pressure will ________. 2 HCl (g) CL₂ (g) + H₂ (g)

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 is ________. 2SO₃ (g) + 2CL₂ (g) 2SO₂CL₂ (g) + O₂ (g)

A) Keq = [SO₂CL₂] [O₂] / [SO₃] [CL₂]
B) Keq = [SO₃] [CL₂] / [SO₂CL₂] [O₂]
C) Keq = [SO₂CL₂]2[O₂] / [SO₃]2[CL₂]2
D) Keq = [SO₃]2[CL₂]2 / [SO₂CL₂]2[O₂]

Question 14

The following chemical reaction has reached equilibrium. (g) (g) Calculate the equilibrium constant, Keq, if the concentrations of and are 0.0238 M and 0.196 M, respectively.

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

Question 15

The following chemical reaction has reached equilibrium. 2NO (g) + O₂ (g) 2NO₂ (g)
Calculate the equilibrium constant, Keq, if the concentrations of reactants and products are 1.26 × 10^-10 M for NO, 2.28 × 10^-3 M for O₂, and 9.32 × 10^-6 M for NO₂.

A) 2.40 × 10^-12
B) 3.28 × 10^-7
C) 2.61 × 10^-17
D) 2.40 × 10¹²

Question 16

Which of the following statements best describes the rate of the forward 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 17

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

Question 18

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 19

If the value of the equilibrium constant for the forward reaction is 5.0 × 10¹⁰, the value of the equilibrium constant for the reverse reaction is ________.

A) -5.0 × 10³⁰
B) 5.0 × 10^-10
C) 2.0 × 10^-11
D) 2.0 × 10^-10

Question 20

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

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

Question 21

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

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

The equilibrium concentrations for the reaction at 300 K are [CL₂] = 0.75 M, [PCL₃] = 0.45 M, and [PCl5] = 0.73 M. The value of Keq is ________. CL₂ (g) + PCL₃ (g) PCl5 (g)

A) 2.2
B) 0.15
C) 0.048
D) 4.7

Question 23

Adding iron(III) chloride will ________. FeCL₃ (aq) + KSCN (aq) 3[Fe(SCN)6] (aq) + 3KCl (aq)
Yellow colorless red colorless

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

Question 24

Adding a couple of drops of an aqueous KCl solution will ________. FeCL₃ (aq) + KSCN (aq) K3[Fe(SCN)6] (aq) + 3KCl (aq)
Yellow colorless red colorless

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

Question 25

Removing sulfur dioxide as it is formed will ________. 2H₂S (g) + 3O₂ (g) 2SO₂ (g) + 2H₂O (g)

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

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

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

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

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 28

Decreasing the volume will ________. 2SO₃ (g) + 2CL₂ (g) 2SO₂CL₂ (g) + O₂ (g)

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

Removing product will ________. 2SO₂ (g) + O₂ (g) 2SO₃ (g)

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 30

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

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

Question 31

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

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

Decreasing the pressure will ________. 2SO₃ (g) + 2CL₂ (g) 2SO₂CL₂ (g) + O₂ (g)

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 33

Adding more oxygen will ________. 2SO₂ (g) + O₂ (g) 2SO₃ (g)

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

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

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

Adding helium to the reaction vessel will ________. 2H₂S (g) + 3O₂ (g) 2SO₂ (g) + 2H₂O (g)

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

Adding H₂O to the reaction vessel will ________. 2H₂S (g) + 3O₂ (g) 2SO₂ (g) + 2H₂O (g)

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 37

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

A) [N₂O₄] = 0.00140 M; [NO₂] = 0.0172 M
B) [N₂O₄] = 0.00280 M; [NO₂] = 0.0243 M
C) [N₂O₄] = 0.00452 M; [NO₂] = 0.0309 M
D) [N₂O₄] = 0.00840 M; [NO₂] = 0.0572 M

Question 38

Increasing the pressure will ________. 2H₂S (g) + 3O₂ (g) 2SO₂ (g) + 2H₂O (g)

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 39

Adding KSCN will ________. FeCL₃ (aq) + KSCN (aq) K3[Fe(SCN)6] (aq) + 3KCl (aq)
Yellow colorless red colorless

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

Question 40

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

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

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

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

Question 42

Adding a catalyst will ________. FeCL₃ + KSCN K3[Fe(SCN)6] + 3KCl
Yellow colorless red colorless

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

Which of the following will shift the reaction to the right? CH₄ (g) + 2O₂ (g) CO₂ (g) + 2H₂O (g)

A) adding excess oxygen
B) removing carbon dioxide as soon as it is formed
C) increasing the pressure
D) both A and B

Question 44

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 45

Increasing the volume of the system will ________. 2H₂S (g) + 3O₂ (g) 2SO₂ (g) + 2H₂O (g)

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 46

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 47

If the solubility of a certain salt A₂B is 1.4 × 10^-4 M, the value of the solubility product will be ________.

A) 2.7 × 10^-12
B) 1.1 × 10^-11
C) 1.6 × 10^-11
D) 3.6 × 10^-12

Question 48

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

A) Ksp = [Ag+] [SO₄-2]
B) Ksp = [2 Ag+] [SO₄-2]
C) Ksp = [Ag+]2[SO₄-2]
D) Ksp = [2Ag+]2[SO₄-2]

Question 49

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

Question 50

If oxygen is removed this will ________. CH₄ (g) + 2O₂ (g) CO₂ (g) + 2H₂O (g)

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 51

If the reaction vessel is expanded, this will ________. CH₄ (g) + 2O₂ (g) CO₂ (g) + 2H₂O (g)

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 52

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 53

Adding excess oxygen will ________. CH₄ (g) + 2O₂ (g) CO₂ (g) + 2H₂O (g)

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 54

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

Question 55

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 56

For the following exothermic reaction, what condition will increase the yield of product? C₂H₂ (g) + H₂O (g) CH₃CHO (g)

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

Question 57

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 58

The solubility of SrF₂ in water (given Ksp = 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 59

Which of the following will shift the equilibrium to the left? 2H₂S (g) + 3O₂ (g) 2SO₂ (g) + 2H₂O (g)

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

Question 60

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 61

Reducing the pressure will shift the equilibrium to the right.
N₂ (g) + O₂ (g) ⇔ 2NO (g)

Question 62

Decreasing the concentration of nitrogen will shift the equilibrium to the left.
N₂ (g) + 2O₂ (g) ⇔ 2NO₂ (g)

Question 63

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 64

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

Question 65

If more reactants are added to a chemical reaction already at equilibrium, a shift to the products is required to restore an equilibrium condition.

Question 66

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

Question 67

Reducing the pressure will shift the equilibrium to the left.
N₂ (g) + 2O₂ (g) ⇔ 2NO₂ (g)

Question 68

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 69

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

Question 70

If a chemical reaction at an equilibrium state is disturbed, the reaction will compensate for the disturbance in some way so that equilibrium can be restored.

Question 71

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

Question 72

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 73

For the following reaction 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.
N₂H₄ (g) ⇔ 2 H₂ (g) + N₂ (g)

Question 74

An equilibrium condition can be achieved only when 100% of the reactants have been converted to products.

Question 75

A reaction is close to equilibrium when a rapid reverse reaction slows down and a slower forward reaction speeds up.

Question 76

A reaction that favors products has a Keq > 1.

Question 77

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.
PCl5 ⇔ PCL₃ + CL₂

Question 78

A product favored reaction has Keq = 1.

Question 79

A reaction is approaching equilibrium when the rate of a forward reaction slows down and the rate of a reverse reaction speeds up.

Question 80

Reducing the pressure will shift the equilibrium to the right.
CL₂ (g) + 3F₂ (g) ⇔ 2ClF3 (g)