Question 1

Which of the following best describes 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 $$\mathrm{N_2O_4(g) \rightleftharpoons 2 NO_2$(g)}$$, the equilibrium constant expression $$K_c is$$:

Accepted Answer

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

Question 3

A reaction has a very large equilibrium constant $$K. $$What does this indicate about the reaction at equilibrium?

Accepted Answer

The reaction favors the formation of products.

Question 4

Given 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?

Accepted Answer

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

Question 5

If the equilibrium concentrations for the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2 NO_2$(g)}$$ are $$[\mathrm{N_2O_4}] = 0.0045\ \mathrm{M}$$ and $$[\mathrm{NO_2$}] = 0.0310\ \mathrm{M}$$, what is the value of $$K_c$$?

Accepted Answer

$$K_c = 0.214$$

Question 6

Which of the following statements about the equilibrium constant $$K is $$correct?

Accepted Answer

The value of $$K is $$independent of concentration but depends on temperature.

Question 7

For the gas-phase reaction $$aA(g) + bB(g) \rightleftharpoons dD(g) + eE(g)$$, the relationship between $$K_p$$ and $$K_c is$$:

Accepted Answer

$$K_p = K_c(RT$$)^{\Delta n}$$, where $$\Delta n = (d+e)-(a+b)$$

Question 8

A catalyst affects a chemical reaction by:

Accepted Answer

Lowering the activation energy and increasing the rate at which equilibrium is reached

Question 9

Which of the following best explains why the equilibrium constant expression for a reaction is based on stoichiometry and not the reaction mechanism?

Accepted Answer

Because the law of mass action is derived from the balanced chemical equation, not the mechanism.

Question 10

If the equilibrium constant for a reaction written in one direction is $$K$$, what is the equilibrium constant for the reverse reaction?

Accepted Answer

$$1/K$$

Question 11

Consider the following reactions and their equilibrium constants:

$$\mathrm{CO(g) + 2 H_2$(g) ightleftharpoons CH_3OH(g)}$$  $$K_3 = 1.4$$ 	imes $$10^7$$
$$\mathrm{CO_2$(g) + H_2$(g) ightleftharpoons CO(g) + H_2O(g)}$$  $$K_2 = 1.0$$ 	imes $$10^5$$

What is the equilibrium constant for the reaction $$\mathrm{CO_2$(g) + 3 H_2$(g) ightleftharpoons CH_3OH(g) + H_2O(g)}$$?

Accepted Answer

$$K_1 = 140$

Question 12

Which of the following is true about a reaction with a small equilibrium constant $$K$$?

Accepted Answer

The reaction favors the formation of reactants.

Question 13

A saturated solution of NaCl in water is an example of:

Accepted Answer

A dynamic equilibrium

Question 14

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

Accepted Answer

Adding more reactant

Question 15

For the reaction $$\mathrm{2 NO_2$(g) \rightleftharpoons N_2O_4(g)}$$, if $$K_c = 0.25$$ for the forward reaction, what is $$K_c$$ for the reverse reaction?

Accepted Answer

$$K_c = 1/0.25 = 4$$

Question 16

A phase diagram shows the relationship between:

Accepted Answer

Pressure and temperature

Question 17

In the context of photochemistry, what is the role of a photocatalyst?

Accepted Answer

To absorb photons and provide an alternative reaction pathway with lower activation energy

Question 18

Which of the following best describes the effect of temperature on the equilibrium constant $$K$$?

Accepted Answer

The effect of temperature on $$K$$ depends on whether the reaction is exothermic or endothermic.

Dynamic Equilibrium and the Equilibrium Constant in Chemical Reactions

Study Guide - Practice Questions

Study Guide - Flashcards