Question 1

For the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$, which of the following statements best describes the system at equilibrium?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 2

Given the reaction $$\mathrm{2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)}$$, the equilibrium constant $$K_c is $$very large at a certain temperature. What does this imply about the composition of the equilibrium mixture?

Accepted Answer

The mixture contains mostly products.

Question 3

For the reaction $$\mathrm{$$CaCO_3$$(s) \rightleftharpoons CaO(s) + CO_2$(g)}$$, what is the correct expression for the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = [\mathrm{CO_2$}]$$

Question 4

A reaction mixture initially contains only reactants. As the reaction proceeds, the value of $$Q ($$reaction quotient) is monitored. Which of the following is true as the system approaches equilibrium?

Accepted Answer

$$Q$$ increases until it equals $$K.$$

Question 5

For the reaction $$\mathrm{2NO(g) + Cl_2$(g) \rightleftharpoons 2NOCl(g)}$$, $$K_c = 5.3. If$$ $$[NO] = 0.42\ \mathrm{M}$$, $$[Cl_2$] = 0.67\ \mathrm{M}$$, and $$[NOCl] = 0.92\ \mathrm{M}$$, in which direction will the reaction proceed?

Accepted Answer

Toward the reactants (left)

Question 6

Which of the following changes will NOT affect the position of equilibrium for the reaction $$\mathrm{H_2$(g) + I_2$(g) \rightleftharpoons 2HI(g)}$$?

Accepted Answer

Adding an inert gas at constant volume

Question 7

For the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$, which of the following will increase the yield of ammonia ($$\mathrm{NH_3$}) at $$equilibrium?

Accepted Answer

Removing $$\mathrm{NH_3$} as it $$forms

Question 8

A catalyst is added to a reaction at equilibrium. What is the effect on the equilibrium position and the value of $$K$$?

Accepted Answer

The equilibrium is reached faster, but $$K$$ remains unchanged.

Question 9

For the reaction $$\mathrm{2HI(g) \rightleftharpoons H_2$(g) + I_2$(g)}$$, the initial concentration of HI is $$0.100\ \mathrm{M}$$ and at equilibrium it is $$0.078\ \mathrm{M}. $$What is the value of $$K_c$$?

Accepted Answer

$$K_c = 0.039$$

Question 10

Which of the following best describes the effect of increasing temperature on the equilibrium constant $$K$$ for an exothermic reaction?

Accepted Answer

$$K$$ decreases

Question 11

For the reaction $$\mathrm{2X(g) + Y_2$(g) \rightleftharpoons X_2Y(g) + Y(g)}$$ with $$\Delta H \u003e 0$$, what will happen to $$[Y_2$] if $$the temperature is increased?

Accepted Answer

$$[Y_2$]$$ will decrease

Question 12

A sealed container at equilibrium contains $$\mathrm{$$COCl_2$$(g)}$$, $$\mathrm{CO(g)}$$, and $$\mathrm{Cl_2$(g)}. If $$more $$\mathrm{$$COCl_2$$} is $$added, what will happen to the concentrations of $$\mathrm{CO}$$ and $$\mathrm{Cl_2$}$$?

Accepted Answer

Both will increase

Question 13

For the reaction $$\mathrm{A(g) ightleftharpoons B(g)}$$, $$K_c = 0.43 at$$ $$175^\circC. If a $$mixture has $$[A] = 2.8 	imes 10$$^{-4}$$\ \mathrm{M}$$ and $$[B] = 1.2 	imes 10$$^{-4}$$\ \mathrm{M}$$, what is the value of $$Q_c$$ and in which direction will the reaction proceed?

Accepted Answer

$$Q_c = 0.43$$, no net change

Question 14

Which of the following is true for a heterogeneous equilibrium involving solids and gases?

Accepted Answer

Only the concentrations of gases are included in the equilibrium expression.

Question 15

For the reaction $$\mathrm{2NO_2(g) \rightleftharpoons N_2O_4(g)}$$, how will decreasing the volume of the container affect the equilibrium position?

Accepted Answer

The equilibrium will shift toward the formation of $$\mathrm{N_2O_4}.$$

Question 16

Which of the following is the correct relationship between $$K_p$$ and $$K_c$$ for the reaction $$\mathrm{2A(g) \rightleftharpoons B(g)}$$?

Accepted Answer

$$K_p = K_c(RT$$)^{-1}$$

Question 17

A chemist wants to maximize the yield of $$\mathrm{NH_3$} in $$the Haber process. Which combination of conditions is most effective?

Accepted Answer

Low temperature, high pressure, removal of $$\mathrm{NH_3$}$$

Chemical Equilibrium: The Extent of Chemical Reactions

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