Question 1

Which of the following best describes the state of dynamic equilibrium in a chemical reaction?

Accepted Answer

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

Question 2

For the reaction $$\mathrm{N_2$(g) + 3H_2(g) ightleftharpoons 2NH_3(g)}$$, the equilibrium constant $$K_c is$$ $$3.7 	imes 10^8$ at 25°C. What does this value of K_c$ indicate about the position of equilibrium?

Accepted Answer

The reaction is product-favored and there will be much more $$\mathrm{NH_3$} at $$equilibrium.

Question 3

Given the reaction $$\mathrm{2NO_2(g) \rightleftharpoons N_2O_4(g)}$$, which of the following is the correct expression for the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = \dfrac{[N_2O_4]}{[NO_2$]^2}$$

Question 4

A reaction mixture at equilibrium is disturbed by adding more reactant. According to Le Châtelier’s principle, what will happen?

Accepted Answer

The equilibrium will shift to produce more products.

Question 5

For the reaction $$\mathrm{2CO(g) \rightleftharpoons CO_2$(g) + C(s)}$$, which species are included in the equilibrium constant expression?

Accepted Answer

Only $$\mathrm{CO(g)}$$ and $$\mathrm{CO_2$(g)}$$

Question 6

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

Accepted Answer

The reaction is reactant-favored.

Question 7

Consider the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$ with $$K_c = 0.36 at 100$$°C. If the initial concentration of $$\mathrm{NO_2$} is 0.100 M $$and $$\mathrm{N_2O_4} is 0 M$$, what is the direction of the reaction?

Accepted Answer

The reaction will proceed to the left (reverse).

Question 8

Which of the following changes will NOT affect the position of equilibrium for a chemical reaction?

Accepted Answer

Adding a catalyst.

Question 9

For the reaction $$\mathrm{H_2$(g) + I_2$(g) \rightleftharpoons 2HI(g)}$$, what is the effect of decreasing the volume of the reaction vessel?

Accepted Answer

There will be no shift in equilibrium because the number of gas molecules is the same on both sides.

Question 10

A reaction has the following equilibrium constant: $$K = \dfrac{[NO_2$]^4[O_2$]}{[N_2O_5]^2}. If $$the equation is reversed and all coefficients are divided by 2, what is the new equilibrium constant $$K' in $$terms of $$K$$?

Accepted Answer

$$K' = 1/K$$^{1/2}$$

Question 11

Which of the following best explains why solids and liquids are not included in equilibrium constant expressions?

Accepted Answer

Their concentrations are constant and do not change during the reaction.

Question 12

A reaction mixture at 1000°C initially contains 2.0 mol SO$$_2(g) $$and 2.0 mol O$$_2(g) in a 1.0 L $$container. At equilibrium, there are 1.84 mol SO$$_3. $$What is the equilibrium concentration of O$$_2$$?

Accepted Answer

1.08 M

Question 13

Which of the following statements about the effect of temperature on equilibrium is correct for an exothermic reaction?

Accepted Answer

Increasing temperature shifts the equilibrium to the left.

Question 14

For the reaction $$\mathrm{N_2$(g) + O_2$(g) \rightleftharpoons 2NO(g)}$$, $$K is $$very small. What does this mean in the context of atmospheric chemistry?

Accepted Answer

Very little NO is formed under normal atmospheric conditions.

Question 15

A catalytic converter in a car uses a catalyst to speed up the conversion of CO to CO$$_2. $$What is the effect of the catalyst on the equilibrium position of the reaction?

Accepted Answer

It does not change the equilibrium position.

Question 16

If $$K_c$$ for a reaction is 1.1 × 10$$^{-10}$$, which of the following is true?

Accepted Answer

The reaction is strongly reactant-favored.

Question 17

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

Accepted Answer

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

Question 18

A reaction mixture contains only products at a certain time. What is the value of the reaction quotient $$Q$$ and what will happen?

Accepted Answer

$$Q = \infty$$; the reaction will proceed in the reverse direction.

CHEM 131 Chapter 16: Chemical Equilibrium – Structured Study Notes

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