Q: For the reaction $$\mathrm{N_2$(g) + 3 H_2$(g) \rightleftharpoons 2 NH_3$(g)}$$, $$K_c = 5.8 \times 10^5$ at 25$$^\circ$$C. If $$[$$N_2$$] = 0.10\ \mathrm{M}$$, $$[$$H_2$$] = 0.10\ \mathrm{M}$$, and $$[$$NH_3$$] = 0.01\ \mathrm{M}$$, what is the value of Q$ and in which direction will the reaction proceed to reach equilibrium?

$$Q = 1.0 \times 10$$^{-2}$$, reaction proceeds forward.

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.

Question 2

For the reaction $$\mathrm{N_2$(g) + 3 H_2$(g) \rightleftharpoons 2 NH_3$(g)}$$, which of the following is the correct equilibrium constant expression ($$K_c$$)?

Accepted Answer

$$K_c = \dfrac{[NH_3$]^2}{[N_2$][H_2$]^3}$$

Question 3

A catalyst is added to a reaction at equilibrium. What is its effect?

Accepted Answer

It decreases the time needed to reach equilibrium.

Question 4

Which of the following equilibrium constants indicates a reaction that is strongly product-favored?

Accepted Answer

$$K_c = 1.1 	imes 10$$^{9}$$

Question 5

For the reaction $$\mathrm{S_8$(s) + 8 O_2$(g) \rightleftharpoons 8 SO_2$(g)}$$, which species is omitted from the equilibrium constant expression?

Accepted Answer

$$S_8$$

Question 6

Given the reaction $$\mathrm{2 NO_2$(g) \rightleftharpoons 2 NO(g) + O_2$(g)}$$, write the expression for $$K_c.$$

Accepted Answer

$$K_c = \dfrac{[NO]^2[O_2$]}{[NO_2$]^2}$$

Question 7

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

Accepted Answer

The reaction is reactant-favored.

Question 8

For the reaction $$\mathrm{H_2$(g) + I_2$(g) \rightleftharpoons 2 HI(g)}$$, initial concentrations are $$[H_2$] = 0.0100\ \mathrm{M}$$, $$[I_2$] = 0.00800\ \mathrm{M}$$, and at equilibrium $$[I_2$] = 0.00560\ \mathrm{M}. $$What is $$K_c$$?

Accepted Answer

$$K_c = 0.541$$

Question 9

Which change will shift the equilibrium to the right for the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2 NO_2$(g)}$$?

Accepted Answer

Increasing the volume of the container.

Question 10

For the reaction $$\mathrm{N_2$(g) + 3 H_2$(g) ightleftharpoons 2 NH_3$(g)}$$, $$K_c = 5.8 	imes 10^5$ at 25$$^\circ$$C. If $$[$$N_2$$] = 0.10\ \mathrm{M}$$, $$[$$H_2$$] = 0.10\ \mathrm{M}$$, and $$[$$NH_3$$] = 0.01\ \mathrm{M}$$, what is the value of Q$ and in which direction will the reaction proceed to reach equilibrium?

Accepted Answer

$$Q = 1.0 	imes 10$$^{-2}$$, reaction proceeds forward.

Question 11

Which of the following will NOT affect the value of the equilibrium constant $$K_c$$ for a reaction?

Accepted Answer

Adding a catalyst.

Question 12

For the reaction $$\mathrm{A(g) \rightleftharpoons B(g) + C(g)}$$, $$K_c = 2.5. If$$ $$[A]_{initial} = 0.100\ \mathrm{M}$$ and $$[B]_{initial} = [C]_{initial} = 0$$, what is $$[A] at $$equilibrium?

Accepted Answer

$$[A] = 0.0037\ \mathrm{M}$$

Question 13

Which of the following changes will increase the yield of ammonia in the Haber-Bosch process ($$\mathrm{N_2$(g) + 3 H_2$(g) \rightleftharpoons 2 NH_3$(g)}$$, $$\Delta H^\circ = -92.2\ \mathrm{kJ}$$)?

Accepted Answer

Increasing the pressure.

Question 14

For the reaction $$\mathrm{CO(g) + H_2O(g) \rightleftharpoons CO_2$(g) + H_2$(g)}$$, what effect does increasing the pressure have on the equilibrium?

Accepted Answer

The equilibrium remains unchanged.

Question 15

If the temperature of an endothermic reaction at equilibrium is increased, what happens to the value of $$K_c$$?

Accepted Answer

$$K_c$$ increases.

Question 16

For the reaction $$\mathrm{2 NOCl(g) \rightleftharpoons 2 NO(g) + Cl_2$(g)}$$, 2.00 mol NOCl is placed in a 1.00 L flask. At equilibrium, 0.66 mol NO is present. What is $$K_c$$?

Accepted Answer

$$K_c = 0.214$$

Question 17

Which of the following is true about the reaction quotient $$Q$$?

Accepted Answer

$$Q$$ can predict the direction a reaction will proceed to reach equilibrium.

Question 18

For the reaction $$\mathrm{C(s) + CO_2$(g) \rightleftharpoons 2 CO(g)} in a 2 L $$flask containing 0.10 mol CO, 0.20 mol CO$$_2$$, and 0.40 mol C at equilibrium, what is the value of $$K_c$$?

Accepted Answer

$$K_c = 8.0$$

Chemical Equilibrium: Principles, Constants, and Applications

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