Q: A reaction mixture at equilibrium contains $$[A] = 0.2 M$$, $$[B] = 0.3 M$$, $$[C] = 0.4 M$$, and $$[D] = 0.5 M $$for the reaction $$A + 2B \rightleftharpoons 3C + D. $$What is the value of $$K_c$$?

$$K_c = \frac{[C]^3 [D]}{[A][B]^2} = \frac{(0.4)^3$ \times 0.5}{0.2 \times (0.3)^2$} = 4.44$$

Question 1

For the reaction $$aA + bB \rightleftharpoons cC + dD$$, which of the following is the correct expression for the equilibrium constant $$K_c in $$terms of concentrations?

Accepted Answer

$$K_c = \frac{[C]^c [D]^d}{[A]^a [B]^b}$$

Question 2

Consider the reaction $$2HI(g) \rightleftharpoons H_2$(g) + I_2$(g). $$Which of the following is the correct equilibrium constant expression in terms of partial pressures ($$K_p$$)?

Accepted Answer

$$K_p = \frac{P_{H_2$} P_{I_2$}}{P_{HI}^2}$$

Question 3

A reaction mixture at equilibrium contains $$[A] = 0.2 M$$, $$[B] = 0.3 M$$, $$[C] = 0.4 M$$, and $$[D] = 0.5 M $$for the reaction $$A + 2B \rightleftharpoons 3C + D. $$What is the value of $$K_c$$?

Accepted Answer

$$K_c = \frac{[C]^3 [D]}{[A][B]^2} = \frac{(0.4)^3$ 	imes 0.5}{0.2 	imes (0.3)^2$} = 4.44$$

Question 4

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

Accepted Answer

The value of $$K is $$constant at a given temperature.

Question 5

For the reaction $$N_2O_4(g) \rightleftharpoons 2NO_2(g)$$, the equilibrium constant in terms of pressure is $$K_p = \frac{P_{NO_2$}^2}{P_{N_2O_4}}. If$$ $$K_p is $$much less than 1, what does this indicate about the equilibrium mixture?

Accepted Answer

The mixture contains mostly $$N_2O_4 at $$equilibrium.

Question 6

Which of the following is NOT included in the equilibrium constant expression for the reaction $$2H_2O(l) \rightleftharpoons 2H_2(g) + O_2$(g)$$?

Accepted Answer

$$[H_2O]$$

Question 7

For the reaction $$aA(g) + bB(g) \rightleftharpoons cC(g) + dD(g)$$, the relationship between $$K_p$$ and $$K_c is $$given by $$K_p = K_c(RT$$)^{\Delta n}$$. What does $$\Delta n$$ represent?

Accepted Answer

The difference between the moles of gaseous products and gaseous reactants.

Question 8

A reaction at equilibrium is subjected to an increase in temperature. If the reaction is endothermic, what will happen to the value of the equilibrium constant $$K$$?

Accepted Answer

The value of $$K$$ will increase.

Question 9

In a simulation of the reaction $$A \rightleftharpoons B$$, increasing the temperature resulted in more B and less A at equilibrium. What can you conclude about the reaction?

Accepted Answer

The reaction is endothermic in the forward direction.

Question 10

For the reaction $$2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)$$, which of the following is the correct $$K_p$$ expression?

Accepted Answer

$$K_p = \frac{P_{SO_3$}^2}{P_{SO_2$}^2 P_{O_2$}}$$

Question 11

A beaker contains a mixture of red and blue molecules at equilibrium for the reaction $$A_{(g)} \rightleftharpoons B_{(g)}. If $$the equilibrium constant $$K is $$large, which of the following best describes the mixture?

Accepted Answer

There are more blue molecules than red molecules.

Question 12

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

Accepted Answer

Adding a catalyst.

Question 13

For the reaction $$2NO_2(g) \rightleftharpoons N_2O_4(g)$$, if the initial pressure of $$NO_2 is 2.0 $$bar and at equilibrium it is 0.5 bar, what is the equilibrium pressure of $$N_2O_4$$?

Accepted Answer

0.75 bar

Question 14

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

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 15

For the reaction $$2HgO(s) \rightleftharpoons 2Hg(l) + O_2$(g)$$, which of the following is the correct equilibrium constant expression?

Accepted Answer

$$K = P_{O_2$}$$

Question 16

If the equilibrium constant $$K$$ for a reaction is $$1.0 	imes 10^7$, what does this indicate about the position of equilibrium?

Accepted Answer

The reaction proceeds nearly to completion.

Question 17

For the reaction $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$, what is the value of $$\Delta n$$ used in the equation K_p = K$$_$$c(RT)^{\Delta n}$$?

Accepted Answer

$$\Delta n = 2 - (1+3) = -2$$

Question 18

Which of the following is a correct statement about the units of $$K_c$$ and $$K_p$$?

Accepted Answer

The units of $$K_c$$ depend on the reaction stoichiometry.

Question 19

A reaction mixture is at equilibrium. If more reactant is added, what will happen to the system?

Accepted Answer

The system will shift to produce more products.

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