Question 1

Which of the following best describes the concept of dynamic equilibrium in a chemical system?

Accepted Answer

The rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant over time.

Question 2

Refer to the phase diagram of water. At which point do all three phases (solid, liquid, gas) coexist in equilibrium?

Accepted Answer

Triple point

Question 3

A saturated solution, such as the one shown in the first image, is an example of which type of equilibrium?

Accepted Answer

Dynamic equilibrium between dissolved ions and undissolved solid

Question 4

For the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2 NO_2$(g)}$$, which of the following is the correct equilibrium constant expression in terms of concentration?

Accepted Answer

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

Question 5

In the context of the Haber process, which of the following best explains why high pressure is used?

Accepted Answer

High pressure shifts the equilibrium toward ammonia production because there are fewer moles of gas on the product side.

Question 6

Given the reaction $$\mathrm{N_2$(g) + 3 H_2$(g) \rightleftharpoons 2 NH_3$(g)}$$, which is the correct equilibrium constant expression?

Accepted Answer

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

Question 7

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

Accepted Answer

$$K_c = \frac{(0.0310)^2$}{0.0045} = 0.2138$$

Question 8

Which of the following statements about equilibrium constants is TRUE?

Accepted Answer

The equilibrium constant is dependent on temperature but independent of initial concentrations.

Question 9

For the reaction $$\mathrm{2 NO(g) + 2 H_2$(g) \rightleftharpoons N_2$(g) + 2 H_2O(g)} at 500$$°C, $$K_c = 654. $$What is the value of $$K_p at $$this temperature? (Assume $$R = 0.08206\ L\cdot atm/(mol\cdot K)$$ and $$T = 773\ K)$$

Accepted Answer

$$K_p = K_c(RT$$)^{\Delta n}$$, where $$\Delta n = (1+2)-(2+2) = -1$$. K_p = 654$$ 	imes (0.08206 	imes $$773)^{-1}$$ \approx 10.3$$

Question 10

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

Accepted Answer

Concentration of a pure solid

Question 11

A student claims that at equilibrium, the concentrations of reactants and products must be equal. Is this statement correct? Why or why not?

Accepted Answer

No, because equilibrium means the rates of the forward and reverse reactions are equal, not the concentrations.

Question 12

Which of the following best explains why the color of the gas in the test tube in the third image changes from colorless to brown upon warming?

Accepted Answer

Warming causes $$\mathrm{N_2O_4} to $$dissociate into $$\mathrm{NO_2$}$$, which is brown.

Question 13

Which of the following is the correct relationship between $$K_p$$ and $$K_c$$ for a reaction involving gases?

Accepted Answer

$$K_p = K_c(RT$$)^{\Delta n}$$

Question 14

In the context of chemical equilibrium, what does the term 'activity' refer to?

Accepted Answer

A dimensionless quantity approximated by concentration or pressure under ideal conditions

Question 15

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 16

A reaction mixture initially contains only reactants. As the reaction proceeds toward equilibrium, what happens to the rates of the forward and reverse reactions?

Accepted Answer

The rate of the forward reaction decreases and the rate of the reverse reaction increases until they are equal at equilibrium.

Question 17

Which of the following best describes the effect of a catalyst on a system at equilibrium?

Accepted Answer

A catalyst increases the rate at which equilibrium is achieved but does not affect the equilibrium position.

Question 18

In the Haber process, why is it important to recycle unreacted $$\mathrm{N_2$}$$ and $$\mathrm{H_2$}$$ gases?

Accepted Answer

To increase the overall yield of ammonia by allowing unreacted gases additional opportunities to react.

Question 19

Which of the following is a correct statement about the equilibrium constant for a reaction?

Accepted Answer

It can be greater than, less than, or equal to 1, depending on the reaction.

Chemical Equilibrium: Principles, Expressions, and Applications

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