Q: For the reaction $$2 \\text{NO}_2 (g) \\rightleftharpoons 2 \\text{NO} (g) + \\text{O}_2 (g)$$, which of the following is the correct equilibrium constant expression?

$$K = \\frac{[\\text{NO}]^2 [\\text{O}_2]}{[\\text{NO}_2]^2}$$

Q: Which of the following reactions will have $$K_p = K_c at a $$given temperature?

$$H_2 (g$$) + $$I_2 (g$$) \\rightleftharpoons 2 HI (g)$$

Q: A reaction mixture at equilibrium contains $$[A] = 0.20 M$$, $$[B] = 0.10 M$$, and $$[C] = 0.40 M $$for the reaction $$A (g) + 2 B (g) \\rightleftharpoons C (g). $$What is the value of $$K_c$$?

$$K_c = \\frac{[C]}{[A][B]^2} = \\frac{0.40}{0.20 \\times (0.10)^2$} = 200$$

Q: For the reaction $$2 NO (g) + Br_2$ (g) \\rightleftharpoons 2 NOBr (g)$$, $$K_p = 2.5 \\times 10^2$ at 35ºC. If the equilibrium partial pressures are P$$_{NO} = 0.2$$ atm and P$$_{$$Br_2$$} = 0.050$$ atm, what is the equilibrium partial pressure of $$NOBr$$?

$$P_{NOBr} = \\sqrt{K_p \\times P_{NO}^2 \\times P_{Br_2$}} = \\sqrt{2.5 \\times 10^2$ \\times (0.2)^2$ \\times 0.05} = 1.58$$ atm

Question 1

Which of the following best describes chemical equilibrium in a closed system?

Accepted Answer

The rates of the forward and reverse reactions are equal, and concentrations of reactants and products remain constant.

Question 2

For the reaction $$2 \text{NO}_2 (g) \rightleftharpoons 2 \text{NO} (g) + \text{O}_2 (g)$$, which of the following is the correct equilibrium constant expression?

Accepted Answer

$$K = \frac{[\text{NO}]^2 [\text{O}_2]}{[\text{NO}_2]^2}$$

Question 3

Which of the following changes will NOT affect the position of equilibrium for a reaction at constant temperature?

Accepted Answer

Adding a catalyst

Question 4

Given the reaction $$N_2 (g) + 3$$ $$H_2 (g$$) \rightleftharpoons 2 $$NH_3 (g$$)$$, what will happen if the volume of the container is decreased at constant temperature?

Accepted Answer

The equilibrium will shift to the right, favoring ammonia formation.

Question 5

For the reaction $$2 SO_2$ (g) + O_2$ (g) \rightleftharpoons 2 SO_3$ (g)$$, if the equilibrium constant $$K_c is$$ $$4.5 at a $$certain temperature, what is the value of $$K_c$$ for the reverse reaction?

Accepted Answer

$$K_c = 0.222$$

Question 6

Which of the following reactions will have $$K_p = K_c at a $$given temperature?

Accepted Answer

$$H_2 (g$$) + $$I_2 (g$$) \rightleftharpoons 2 HI (g)$$

Question 7

A reaction mixture at equilibrium contains $$[A] = 0.20 M$$, $$[B] = 0.10 M$$, and $$[C] = 0.40 M $$for the reaction $$A (g) + 2 B (g) \rightleftharpoons C (g). $$What is the value of $$K_c$$?

Accepted Answer

$$K_c = \frac{[C]}{[A][B]^2} = \frac{0.40}{0.20 \times (0.10)^2$} = 200$$

Question 8

For the reaction $$2 NOBr (g) \rightleftharpoons 2 NO (g) + Br_2$ (g)$$, if $$K_c = 0.75 at 750 K $$and the initial concentrations are $$[NOBr] = 1.25 M$$, $$[NO] = 0.80 M$$, $$[Br_2$] = 0.50 M$$, what will happen to the system?

Accepted Answer

The reaction will shift to the left, increasing [NOBr].

Question 9

Which of the following statements about the equilibrium constant $$K is $$correct?

Accepted Answer

$$K is $$only affected by temperature changes.

Question 10

For the reaction $$2 NO (g) + Br_2$ (g) \rightleftharpoons 2 NOBr (g)$$, $$K_p = 2.5 \times 10^2$ at 35ºC. If the equilibrium partial pressures are P$$_{NO} = 0.2$$ atm and P$$_{$$Br_2$$} = 0.050$$ atm, what is the equilibrium partial pressure of $$NOBr$$?

Accepted Answer

$$P_{NOBr} = \sqrt{K_p \times P_{NO}^2 \times P_{Br_2$}} = \sqrt{2.5 \times 10^2$ \times (0.2)^2$ \times 0.05} = 1.58$$ atm

Question 11

If $$K_p$$ increases with increasing temperature for a reaction, what can you conclude about the reaction?

Accepted Answer

The reaction is endothermic.

Question 12

For the reaction $$2 SO_2$ (g) + O_2$ (g) \rightleftharpoons 2 SO_3$ (g)$$, if the equilibrium constant for the forward reaction is $$K$$, what is the equilibrium constant for the reaction $$SO_3 (g$$) \rightleftharpoons $$SO_2 (g) + 0.5$$ $$O_2 (g$$)$$?

Accepted Answer

$$K^{-0.5}$$

Question 13

Which of the following will increase the yield of products for the reaction $$CH_4 (g) + 4$$ $$F_2 (g$$) \rightleftharpoons $$CF_4 (g) + 4 HF (g$$)$$, $$\Delta H = 38.2$$ kJ/mol?

Accepted Answer

Increase the temperature

Question 14

For the reaction $$A (g) \rightleftharpoons B (g) + C (g)$$, if $$k_{forward} = 5.7 \times 10$$^{-2}$$ and k$$_{reverse} = 3.8 \times $$10^{-4}$$, which will be greater at equilibrium?

Accepted Answer

Partial pressures of B and C

Question 15

Which of the following is NOT true if $$Q \u003e K$$ for a reaction mixture?

Accepted Answer

The reaction will shift to the right to form more products.

Question 16

For the reaction $$2 CO_2$ (g) \rightleftharpoons 2 CO (g) + 2 O_2$ (g)$$, $$K = 3.12 \times 10$$^{-4}$$ at 400 K, and Q = 4.18$$ \times $$10^{-4}. $$Which statement is NOT true?

Accepted Answer

The pressure of $$O_2$$ will be greater than 0.15 atm.

Question 17

Which of the following is excluded from the equilibrium constant expression?

Accepted Answer

Pure solids and pure liquids

Question 18

If the equilibrium constant for a reaction is much greater than 1, what does this indicate about the reaction at equilibrium?

Accepted Answer

Products are favored over reactants.

Chemical Equilibrium: Concepts, Calculations, and Applications

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