Q: Given the reaction $$2\text{NH}_3(g) \rightleftharpoons \text{N}_2(g) + 3\text{H}_2(g)$$, and the equilibrium concentrations $$[\text{NH}_3] = 2.00 \times 10$$^{-4}$$\ \text{mol/L}$$, $$[\text{N}_2] = 1.50 \times 10$$^{-5}$$\ \text{mol/L}$$, $$[\text{H}_2] = 3.45 \times 10$$^{-1}$$\ \text{mol/L}$$, calculate $$K.$$

$$K = \frac{[N_2$][H_2$]^3}{[NH_3$]^2} = \frac{(1.50 \times 10$$^{-5}$$)(3.45 \times 10$$^{-1}$$)^3$$}{(2.00 \times $$10^{-4})^2$} = 15.4$$

Q: For the reaction $$CO(g) + 2H_2(g) \rightleftharpoons CH_3OH(g)$$, if $$[CO] = 0.079\ \text{mol/L}$$, $$[H_2$] = 0.158\ \text{mol/L}$$, and $$[CH_3OH] = 0.021\ \text{mol/L} at $$equilibrium, what is the value of $$K$$?

$$K = \frac{[CH_3OH]}{[CO][H_2$]^2} = \frac{0.021}{0.079 \times (0.158)^2$} = 11$$

Question 1

Which of the following best describes the equilibrium law for the general reaction $$aA + bB \rightleftharpoons cC + dD$$?

Accepted Answer

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

Question 2

For the reaction $$2	ext{NOCl}(g) ightleftharpoons 2	ext{NO}(g) + 	ext{Cl}_2(g)$$, which is the correct equilibrium law expression?

Accepted Answer

$$K = \frac{[NO]^2 [Cl_2$]}{[NOCl]^2}$$

Question 3

A reaction has an equilibrium constant $$K = 1.5 	imes 10$$^{-10}$$ at a certain temperature. What does this indicate about the equilibrium position?

Accepted Answer

The reaction strongly favors the reactants.

Question 4

Given the reaction $$2	ext{NH}_3(g) ightleftharpoons 	ext{N}_2(g) + 3	ext{H}_2(g)$$, and the equilibrium concentrations $$[	ext{NH}_3] = 2.00 	imes 10$$^{-4}$$\ 	ext{mol/L}$$, $$[	ext{N}_2] = 1.50 	imes 10$$^{-5}$$\ 	ext{mol/L}$$, $$[	ext{H}_2] = 3.45 	imes 10$$^{-1}$$\ 	ext{mol/L}$$, calculate $$K.$$

Accepted Answer

$$K = \frac{[N_2$][H_2$]^3}{[NH_3$]^2} = \frac{(1.50 	imes 10$$^{-5}$$)(3.45 	imes 10$$^{-1}$$)^3$$}{(2.00 	imes $$10^{-4})^2$} = 15.4$$

Question 5

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

Accepted Answer

It is constant for a given reaction at a specific temperature.

Question 6

For the heterogeneous equilibrium $$	ext{CaCO}_3(s) ightleftharpoons 	ext{CaO}(s) + 	ext{CO}_2(g)$$, what is the correct equilibrium law expression?

Accepted Answer

$$K = [CO_2$]$$

Question 7

Which of the following best explains why the concentrations of pure solids and liquids are omitted from equilibrium law expressions?

Accepted Answer

Their concentrations are constant and do not affect the equilibrium position.

Question 8

If the equilibrium constant for a reaction is $$K = 4.26 	imes 10^8$ at 25°C and K = 8.00$$ 	imes $$10^{-7} at 400$$°C, what can you conclude?

Accepted Answer

The reaction favors reactants more at higher temperature.

Question 9

Which of the following is the correct equilibrium law expression for the reaction $$2	ext{NaHCO}_3(s) ightleftharpoons 	ext{Na}_2	ext{CO}_3(s) + 	ext{CO}_2(g) + 	ext{H}_2	ext{O}(g)$$?

Accepted Answer

$$K = [CO_2$][H_2O]$$

Question 10

A chemist finds that the equilibrium constant for a reaction is the reciprocal of the equilibrium constant for the reverse reaction. Which of the following best explains this observation?

Accepted Answer

The equilibrium law equation for the reverse reaction is the inverse of the forward reaction.

Question 11

For the reaction $$CO(g) + 2H_2(g) ightleftharpoons CH_3OH(g)$$, if $$[CO] = 0.079\ 	ext{mol/L}$$, $$[H_2$] = 0.158\ 	ext{mol/L}$$, and $$[CH_3OH] = 0.021\ 	ext{mol/L} at $$equilibrium, what is the value of $$K$$?

Accepted Answer

$$K = \frac{[CH_3OH]}{[CO][H_2$]^2} = \frac{0.021}{0.079 	imes (0.158)^2$} = 11$$

Question 12

Which of the following best describes a homogeneous equilibrium?

Accepted Answer

All reactants and products are in the same state of matter.

Question 13

Which of the following is true about the relationship between the equilibrium constant $$K$$ and the rate constants $$k_f$$ and $$k_r$$ for an elementary reaction?

Accepted Answer

$$K = \frac{k_f}{k_r}$$

Question 14

For the reaction $$2CO_2(g) \rightleftharpoons 2CO(g) + O_2$(g)$$, what is the correct equilibrium law expression?

Accepted Answer

$$K = \frac{[CO]^2 [O_2$]}{[CO_2$]^2}$$

Question 15

A reaction has $$K \approx 1 at a $$certain temperature. What does this indicate about the equilibrium mixture?

Accepted Answer

The concentrations of products and reactants are similar.

Question 16

Which of the following is the correct equilibrium law expression for the reaction $$2H_2O(l) \rightleftharpoons 2H_2(g) + O_2$(g)$$?

Accepted Answer

$$K = [H_2$]^2 [O_2$]$$

Question 17

Which of the following best describes a heterogeneous equilibrium?

Accepted Answer

Reactants and products are in at least two different states.

Question 18

If the equilibrium constant for the formation of methanol gas from carbon monoxide and hydrogen is $$K = 6.3 	imes 10$$^{23}$$ at 225°C, what can you predict about the equilibrium mixture?

Accepted Answer

The equilibrium mixture will contain mostly methanol gas.

Lesson 7.2: Equilibrium Law and the Equilibrium Constant (12 Chem)

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