Question 1

The equilibrium constant, $K$, for a reaction is defined as the ratio of the concentrations of which of the following at equilibrium?

Accepted Answer

Products to reactants

Question 2

For the reaction $2 	ext{NO}_2 (g) ightleftharpoons 2 	ext{NO} (g) + 	ext{O}_2 (g)$, the equilibrium constant $K$ is $6.9 	imes 10^2$. If the concentrations at equilibrium are $[	ext{NO}] = 1.5 	imes 10^{-2} 	ext{M}$, $[	ext{O}_2] = 4.3 	imes 10^{-3} 	ext{M}$, and $[	ext{NO}_2] = x$, what is the value of $x$?

Accepted Answer

$x = 2.2 	imes 10^{-2}$

Question 3

If the equilibrium constant $K$ for a reaction is much greater than 1, which of the following statements is true?

Accepted Answer

Products are favored at equilibrium

Question 4

Given the reaction $N_2 (g) + O_2 (g) ightleftharpoons 2 NO (g)$ and $K = 1.0 	imes 10^{-5}$, which is present in greater amount at equilibrium?

Accepted Answer

N_2 (g) and O_2 (g)

Question 5

Which of the following is NOT included in the equilibrium constant expression?

Accepted Answer

Solids

Question 6

For the reaction $2 SO_2 (g) + O_2 (g) \rightleftharpoons 2 SO_3 (g)$, write the correct equilibrium constant expression.

Accepted Answer

$K = \frac{[SO_3]^2}{[SO_2]^2 [O_2]}$

Question 7

A reaction has $K = 1$. What does this indicate about the concentrations of reactants and products at equilibrium?

Accepted Answer

Reactants and products are present in roughly equal amounts

Question 8

For the reaction $2 BrCl (g) \rightleftharpoons Br_2 (g) + Cl_2 (g)$ with $K = 1$, which statement is correct?

Accepted Answer

All species are present in comparable amounts

Question 9

If the equilibrium constant for a reaction is very small, which direction is favored?

Accepted Answer

Reverse (reactants)

Question 10

Which of the following would increase the value of the equilibrium constant $K$ for an exothermic reaction?

Accepted Answer

Decreasing the temperature

Question 11

For the reaction $6 NO (aq) \rightleftharpoons 3 N_2 (aq) + 3 O_2 (aq)$, what is the equilibrium constant expression?

Accepted Answer

$K = \frac{[N_2]^3 [O_2]^3}{[NO]^6}$

Question 12

A student writes the equilibrium expression for $2 Fe^{3+} (aq) + 3 I^- (aq) \rightleftharpoons 2 Fe^{2+} (aq) + I_3^- (aq)$ as $K = \frac{[Fe^{3+}]^2 [I^-]^3}{[Fe^{2+}]^2 [I_3^-]}$. What is the error?

Accepted Answer

The numerator and denominator are reversed

Question 13

Which of the following changes will NOT affect the value of the equilibrium constant $K$?

Accepted Answer

Adding a catalyst

Question 14

In a closed system at equilibrium, which of the following is true?

Accepted Answer

The rates of the forward and reverse reactions are equal

Question 15

For the reaction $2 NO_2 (g) ightleftharpoons 2 NO (g) + O_2 (g)$, if $K = 6.9 	imes 10^2$, which is favored at equilibrium?

Accepted Answer

NO (g) and O_2 (g)

Question 16

A reaction mixture initially contains only reactants. As the reaction proceeds toward equilibrium, what happens to the value of $K$?

Accepted Answer

$K$ remains constant

Chemical Equilibrium and the Equilibrium Constant (K)

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