Question 1

Which of the following is the correct equilibrium constant expression for the reaction:

$$2\ \mathrm{HI}(g) \rightleftharpoons \mathrm{H}_2(g) + \mathrm{I}_2(g)$$

Accepted Answer

$$K = \frac{[\mathrm{H}_2][\mathrm{I}_2]}{[\mathrm{HI}]^2}$$

Question 2

Given the equilibrium constant expression $$K = \frac{[\mathrm{CO}] [\mathrm{H}_2\mathrm{O}]}{[\mathrm{CO}_2][\mathrm{H}_2]} = K_1$ for the reaction $$\mathrm{CO}_2(g) + \mathrm{H}_2(g) \rightleftharpoons \mathrm{CO}(g) + \mathrm{H}_2\mathrm{O}(g)$$, what is the equilibrium constant expression for the reaction 2$$\ \mathrm{CO}_2(g) + 2\ \mathrm{H}_2(g) \rightleftharpoons 2\ \mathrm{CO}(g) + 2\ \mathrm{H}_2\mathrm{O}(g)$$ in terms of K_1$?

Accepted Answer

$$K = K_1$^2$$

Question 3

For the reaction $$2\ \mathrm{NOCl}(g) \rightleftharpoons 2\ \mathrm{NO}(g) + \mathrm{Cl}_2(g)$$, a 0.500 mol sample of NOCl is placed in a 1.00 L vessel and allowed to reach equilibrium at 227°C. If 0.028 mol of $$\mathrm{Cl}_2 is $$present at equilibrium, what is the equilibrium concentration of NOCl?

Accepted Answer

0.444 M

Question 4

Which of the following statements is TRUE regarding the relationship between $$K_c$$ and $$K_p$$ for a gaseous reaction where the number of moles of gaseous products equals the number of moles of gaseous reactants?

Accepted Answer

$$K_c = K_p$$

Question 5

Given the following equilibrium concentrations: $$[\mathrm{HCl}]_{eq} = 0.13\ \mathrm{M}$$, $$[\mathrm{HI}]_{eq} = 5.6 	imes 10$$^{-16}$$\ \mathrm{M}$$, $$[\mathrm{Cl}_2]_{eq} = 0.0019\ \mathrm{M}$$, and $$[\mathrm{I}_2]_{eq} = 0.25\ \mathrm{M}$$ for the reaction $$2\ \mathrm{HI}(g) + \mathrm{Cl}_2(g) ightleftharpoons 2\ \mathrm{HCl}(g) + \mathrm{I}_2(s)$$, what is the value of $$K_c$$?

Accepted Answer

$$K_c = 8.0 	imes 10$$^{28}$$

Question 6

Which of the following is the correct equilibrium constant expression for the reaction: $$\mathrm{H}_2(g) + \mathrm{I}_2(g) \rightleftharpoons 2\ \mathrm{HI}(g)$$?

Accepted Answer

$$K = \frac{[\mathrm{HI}]^2}{[\mathrm{H}_2][\mathrm{I}_2]}$$

Question 7

For the reaction $$2\ \mathrm{HCl}(g) \rightleftharpoons \mathrm{H}_2(g) + \mathrm{Cl}_2(g)$$, which of the following is TRUE regarding $$K_c$$ and $$K_p$$?

Accepted Answer

$$K_c = K_p$$

Question 8

Given the reaction $$3\ \mathrm{H}_2(g) + 3\ \mathrm{Cl}_2(g) \rightleftharpoons 6\ \mathrm{HCl}(g)$$, how is its equilibrium constant $$K_c$$ related to $$K_1$$ for the reaction $$2\ \mathrm{HCl}(g) \rightleftharpoons \mathrm{H}_2(g) + \mathrm{Cl}_2(g)$$?

Accepted Answer

$$K_c = \frac{1}{K_1$^3}$$

Question 9

A chemist mixes $$0.1248\ \mathrm{M}$$ $$\mathrm{H}_2$$ and $$0.0416\ \mathrm{M}$$ $$\mathrm{N}_2 at 500$$°C. At equilibrium, $$[\mathrm{NH}_3] = 0.00272\ \mathrm{M}. $$What is the value of $$K$$ for the reaction $$\mathrm{N}_2(g) + 3\ \mathrm{H}_2(g) \rightleftharpoons 2\ \mathrm{NH}_3(g)$$?

Accepted Answer

$$K = 0.038$$

Question 10

Which of the following would NOT be included in the equilibrium constant expression for a reaction?

Accepted Answer

A pure solid

Question 11

Given the equilibrium constant expression $$K = \frac{[\mathrm{CO}][\mathrm{H}_2\mathrm{O}]}{[\mathrm{CO}_2][\mathrm{H}_2]}$$, what would be the equilibrium constant expression for the reverse reaction?

Accepted Answer

$$K' = \frac{[\mathrm{CO}_2][\mathrm{H}_2]}{[\mathrm{CO}][\mathrm{H}_2\mathrm{O}]}$$

Question 12

A reaction mixture at equilibrium contains $$[\mathrm{NOCl}] = 0.444\ \mathrm{M}$$, $$[\mathrm{NO}] = 0.056\ \mathrm{M}$$, and $$[\mathrm{Cl}_2] = 0.028\ \mathrm{M}. $$What is the value of $$K$$ for the reaction $$2\ \mathrm{NOCl}(g) \rightleftharpoons 2\ \mathrm{NO}(g) + \mathrm{Cl}_2(g)$$?

Accepted Answer

$$K = 0.018$$

Question 13

Which of the following best describes what happens to the value of the equilibrium constant $$K if $$the temperature of an exothermic reaction is increased?

Accepted Answer

$$K$$ decreases

Question 14

For the reaction $$2\ \mathrm{HI}(g) + \mathrm{Cl}_2(g) \rightleftharpoons 2\ \mathrm{HCl}(g) + \mathrm{I}_2(s)$$, which of the following is the correct equilibrium constant expression?

Accepted Answer

$$K = \frac{[\mathrm{HCl}]^2}{[\mathrm{HI}]^2[\mathrm{Cl}_2]}$$

Question 15

A student writes the following equilibrium constant expression for a reaction: $$K = \frac{[\mathrm{CH}_4]}{[\mathrm{CO}][\mathrm{H}_2\mathrm{O}]}. $$Which of the following reactions does this expression correspond to (all species are gases)?

Accepted Answer

$$\mathrm{CO}(g) + \mathrm{H}_2\mathrm{O}(g) \rightleftharpoons \mathrm{CH}_4(g)$$

Question 16

If the equilibrium constant $$K$$ for a reaction is much greater than 1, what does this indicate about the position of equilibrium?

Accepted Answer

Products are favored at equilibrium

Question 17

Which of the following changes will NOT affect the value of the equilibrium constant $$K$$ for a given reaction?

Accepted Answer

Adding a catalyst

Question 18

For the reaction $$\mathrm{N}_2(g) + 3\ \mathrm{H}_2(g) \rightleftharpoons 2\ \mathrm{NH}_3(g)$$, which of the following would increase the yield of ammonia at equilibrium?

Accepted Answer

Increasing the pressure

Question 19

A reaction has $$K = 1.5 	imes 10$$^{-10}$$. Which of the following best describes the composition of the equilibrium mixture?

Accepted Answer

Mostly reactants, very little product

Equilibrium Expressions and Calculations – Step-by-Step Guidance

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