Question 1

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

Accepted Answer

The rate of the forward reaction equals the rate of the reverse reaction, but concentrations of reactants and products remain constant (not necessarily equal).

Question 2

For the reaction $\mathrm{O_2(g) + NO(g) \rightarrow NO_3(g)}$, which is the correct equilibrium constant expression?

Accepted Answer

$K = \dfrac{[NO_3]}{[O_2][NO]}$

Question 3

Which statement about the equilibrium constant $K$ is TRUE?

Accepted Answer

$K$ is always the same for a given reaction at a specific temperature.

Question 4

Given the reaction $2NO_2(g) \rightarrow N_2(g) + 2O_2(g)$, what is the correct equilibrium constant expression?

Accepted Answer

$K = \dfrac{[N_2][O_2]^2}{[NO_2]^2}$

Question 5

For the reaction $HBr(l) \rightarrow H_2(g) + Br_2(g)$, what is the equilibrium constant expression?

Accepted Answer

$K = [H_2][Br_2]$

Question 6

If a reaction has $K \approx 1000$, which of the following best describes the equilibrium mixture?

Accepted Answer

Almost all products, very little reactants

Question 7

Which of the following manipulations of a chemical equation will result in squaring the equilibrium constant $K$?

Accepted Answer

Multiplying all coefficients in the equation by 2

Question 8

For the reaction $S_8(s) + 8SO_2(g) \rightarrow 8SO_3(g)$, which substances are included in the equilibrium constant expression?

Accepted Answer

Only $SO_2$ and $SO_3$

Question 9

Which of the following is the correct $K$ expression for the reaction $3Al(s) + O_2(g) \rightarrow Al_2O_3(s)$?

Accepted Answer

$K = \dfrac{1}{[O_2]^3}$

Question 10

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

Accepted Answer

There are almost all reactants and very little products.

Question 11

Which of the following correctly describes $K_c$ and $K_p$?

Accepted Answer

$K_c$ uses concentrations in molarity (M), $K_p$ uses partial pressures in atmospheres (atm).

Question 12

For the reaction $A \rightarrow B$, if the initial concentration of $B$ is much higher than at equilibrium, which way will the reaction shift?

Accepted Answer

It will shift to the left, forming more reactants.

Question 13

If $Q > K$ for a reaction, what does this indicate and what will happen?

Accepted Answer

There are too many products; the reaction will shift left.

Question 14

A disturbance increases the concentration of a reactant in a system at equilibrium. According to Le Chatelier’s Principle, what will happen?

Accepted Answer

The reaction will shift to the right, forming more products.

Question 15

For the reaction $PCl_3(g) + Cl_2(g) \rightarrow PCl_5(g)$ at equilibrium, what will happen if $PCl_5$ is added to the system?

Accepted Answer

The reaction will shift to the left, forming more $PCl_3$ and $Cl_2$.

Question 16

Which of the following changes will cause a decrease in $Q$ for a reaction at equilibrium?

Accepted Answer

Removing product

Question 17

For the reaction $Mg(s) + 2HCl(aq) \rightarrow MgCl_2(aq) + H_2(g)$, what will happen if $HCl$ is removed from the system at equilibrium?

Accepted Answer

The reaction will shift to the left, forming more reactants.

Question 18

Which of the following is TRUE about the equilibrium constant $K$ for a reaction?

Accepted Answer

$K$ can be anywhere on the number line, but cannot be negative.

Question 19

A reaction is at equilibrium. If a product is removed, which direction will the reaction shift?

Accepted Answer

To the right

Introduction to Chemical Equilibrium

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