Question 1

Which of the following best describes a system at chemical equilibrium?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 2

For the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$, which of the following is true at equilibrium?

Accepted Answer

The concentrations of $$\mathrm{N_2O_4}$$ and $$\mathrm{NO_2$}$$ are constant.

Question 3

Given the equilibrium $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$, the equilibrium constant expression is:

Accepted Answer

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

Question 4

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

Accepted Answer

Products are favored.

Question 5

For the reaction $$\mathrm{2NO_2(g) \rightleftharpoons N_2O_4(g)}$$, if $$K_c = 0.212 at$$ $$100^\circC$$, what is the value of $$K_c$$ for the reverse reaction?

Accepted Answer

$$K_c = 4.72$$

Question 6

A reaction mixture has $$[HI] = 1.87 	imes 10$$^{-3}$$\ \mathrm{M}$$, $$[H_2$] = 6.5 	imes 10$$^{-5}$$\ \mathrm{M}$$, and $$[I_2$] = 1.065 	imes 10$$^{-3}$$\ \mathrm{M} at $$equilibrium. What is the value of $$K_c$$ for $$\mathrm{H_2$(g) + I_2$(g) ightleftharpoons 2HI(g)}$$?

Accepted Answer

$$K_c = 51$$

Question 7

If the reaction quotient $$Q is $$less than the equilibrium constant $$K$$, what will happen to the system?

Accepted Answer

The reaction will shift toward products.

Question 8

For the reaction $$\mathrm{$$CaCO_3$$(s) \rightleftharpoons CaO(s) + CO_2$(g)}$$, which of the following will increase the equilibrium pressure of $$\mathrm{CO_2$}$$?

Accepted Answer

Increasing the temperature (assuming the reaction is endothermic)

Question 9

Which of the following changes will shift the equilibrium of $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)} to $$the right?

Accepted Answer

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

Question 10

A catalyst is added to a reaction at equilibrium. What is the effect on the equilibrium position and the rate at which equilibrium is achieved?

Accepted Answer

The equilibrium position does not change, but equilibrium is reached faster.

Question 11

For the reaction $$\mathrm{2A(g) \rightleftharpoons B(g)}$$, what will happen if the volume of the container is decreased?

Accepted Answer

The equilibrium will shift toward the side with fewer moles of gas.

Question 12

If the equation for a reaction is multiplied by 2, how is the new equilibrium constant related to the original?

Accepted Answer

The new $$K is $$the original $$K$$ squared.

Question 13

Which of the following statements about homogeneous and heterogeneous equilibria is correct?

Accepted Answer

In homogeneous equilibria, all reactants and products are in the same phase.

Question 14

For the reaction $$\mathrm{A(g) + B(g) \rightleftharpoons C(g) + D(g)}$$, if $$K_p is $$the equilibrium constant in terms of pressure and $$K_c is $$the equilibrium constant in terms of concentration, which equation relates $$K_p$$ and $$K_c$$?

Accepted Answer

$$K_p = K_c (RT$$)^{\Delta n}$$

Question 15

A mixture initially contains 1.0 M $$\mathrm{H_2$}$$ and 2.0 M $$\mathrm{I_2$}. At $$equilibrium, $$[HI] = 1.87 M $$for the reaction $$\mathrm{H_2$(g) + I_2$(g) \rightleftharpoons 2HI(g)}. $$What is the equilibrium concentration of $$\mathrm{H_2$}$$?

Accepted Answer

$$0.065 M$$

Question 16

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

Accepted Answer

Adding a catalyst

Question 17

For the reaction $$\mathrm{2NOBr(g) \rightleftharpoons 2NO(g) + Br_2$(g)}$$ with $$K_1 = 0.014$ and $$\mathrm{$$Br_2(g$$) + $$Cl_2(g$$) \rightleftharpoons 2BrCl(g)}$$ with K_2$ = 7.2$$, what is the equilibrium constant for $$\mathrm{2NOBr(g) + Cl_2$(g) \rightleftharpoons 2NO(g) + 2BrCl(g)}$$?

Accepted Answer

$$K = 0.10$$

Chemical Equilibrium: Principles, Calculations, and Applications

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