Q: Which of the following is the correct expression for the activity of a gas in equilibrium calculations?

$$\text{activity} = \text{partial pressure} / 1\,\text{atm}$$

Question 1

Which of the following best describes chemical equilibrium in a reversible reaction?

Accepted Answer

The rate of the forward reaction equals the rate of the reverse reaction.

Question 2

A catalyst is added to a reaction at equilibrium. What effect does this have?

Accepted Answer

It increases the rate at which equilibrium is reached, but does not change $$K.$$

Question 3

For the reaction $$N_2O_4(g) \rightleftharpoons 2NO_2(g)$$, if the concentration of $$NO_2 is $$increased, according to Le Chatelier's Principle, what will happen?

Accepted Answer

The system will shift to the left, producing more $$N_2O_4.$$

Question 4

Which of the following is the correct expression for the activity of a gas in equilibrium calculations?

Accepted Answer

$$	ext{activity} = 	ext{partial pressure} / 1\,	ext{atm}$$

Question 5

If $$Q \u003c K$$ for a reaction, what will happen as the system moves toward equilibrium?

Accepted Answer

Products will be formed.

Question 6

Which of the following statements about the standard state is correct?

Accepted Answer

For solids and liquids, the activity is always 1.

Question 7

Consider the reaction $$A + B \rightleftharpoons C + D$$ with equilibrium constant $$K. If $$the equation is reversed, what is the new equilibrium constant?

Accepted Answer

$$1/K$$

Question 8

For the reaction $$2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)$$, the equilibrium constant $$K is$$ $$0.10. If $$the initial partial pressures are $$SO_2 = 0.200$ atm and O_2$ = 0.200$$ atm, what will happen to the partial pressure of $$O_2 as $$the system reaches equilibrium?

Accepted Answer

It will decrease.

Question 9

If the coefficients in a balanced chemical equation are multiplied by 2, how does the equilibrium constant change?

Accepted Answer

It is squared.

Question 10

A reaction vessel contains $$0.100 M$$ $$NO_2$$ and no $$N_2O_4. $$For the reaction $$N_2O_4(g) \rightleftharpoons 2NO_2(g)$$, $$K_c = 0.36. $$What is the equilibrium concentration of $$N_2O_4$$?

Accepted Answer

$$0.028 M$$

Question 11

Which of the following is true about the relationship between $$\Delta G$$ and equilibrium?

Accepted Answer

At equilibrium, $$\Delta G = 0$$

Question 12

If a chemical system at equilibrium is disturbed by increasing the pressure, which direction will the reaction shift?

Accepted Answer

Toward the side with fewer moles of gas.

Question 13

For the reaction $$N_2(g) + 3H_2(g$$) ightleftharpoons 2NH_3(g) + 	ext{heat}$$, what happens to the equilibrium constant K$ if temperature is increased?

Accepted Answer

$$K$$ decreases.

Question 14

Which of the following is a correct application of the 5% rule in ICE table calculations?

Accepted Answer

If the value of $$x is $$less than 5% of the initial concentration, it can be neglected.

Question 15

If two reactions have equilibrium constants $$K_1$$ and $$K_2$$, and their equations are added to give an overall reaction, what is the equilibrium constant for the overall reaction?

Accepted Answer

$$K_1$$ 	imes $$K_2$$

Question 16

A reaction is exothermic. According to Le Chatelier's Principle, what happens if heat is removed?

Accepted Answer

The reaction shifts right.

Question 17

For the decomposition of hydrogen sulfide gas, $$2H_2S(g) ightleftharpoons 2H_2(g) + S_2$(g)$$, $$K_c = 1.67 	imes 10$$^{-7}$$. If the vessel initially contains 0.0125$ moles of H_2$ dissolved, what is the equilibrium concentration of H_2$?

Accepted Answer

Approximately $$0.0125 M$$

Question 18

Which of the following is true about the effect of temperature on the equilibrium constant $$K$$ for an endothermic reaction?

Accepted Answer

As temperature increases, $$K$$ increases.

Question 19

Which of the following is the correct relationship between $$Q$$, $$K$$, and the direction a reaction will proceed?

Accepted Answer

If $$Q \u003c K$$, the reaction will proceed to the right.

Chemical Equilibrium: Principles, Calculations, and Applications

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