Question 1

Based on the image, which of the following statements best describes the relationship between $$Q_c$$ and $$K_c$$ and the direction in which a reaction will proceed?

Accepted Answer

If $$Q_c \u003e K_c$$, the reaction will shift to the left to reach equilibrium.

Question 2

A reaction mixture has $$Q_c = 0.5$$ and $$K_c = 2.0. $$According to the image, what will happen to the reaction as it proceeds toward equilibrium?

Accepted Answer

The reaction will shift to the right, forming more products.

Question 3

If $$Q_c = K_c$$ for a chemical reaction, what does this indicate about the system?

Accepted Answer

The system is at equilibrium and no net change will occur.

Question 4

For the reaction $$aA + bB \rightleftharpoons cC + dD$$, the reaction quotient is given by
$$
Q_c = \frac{[C]^c[D]^d}{[A]^a[B]^b}

If$$ $$Q_c \u003e K_c$$, what does this mean for the concentrations of products and reactants?

Accepted Answer

There are more products than at equilibrium, so the reaction will shift left.

Question 5

A chemist finds that $$[A] = 0.10 M$$, $$[B] = 0.20 M$$, $$[C] = 0.30 M$$, and $$[D] = 0.40 M $$for the reaction $$A + B \rightleftharpoons C + D$$ with $$K_c = 6.0. $$What is $$Q_c$$ and in which direction will the reaction proceed?

Accepted Answer

$$Q_c = 12$$, reaction shifts left.

Question 6

For the reaction $$2A \rightleftharpoons B + C$$, if $$K_c = 1.0$$ and the initial concentrations are $$[A] = 1.0 M$$, $$[B] = 0.5 M$$, $$[C] = 0.5 M$$, what is $$Q_c$$ and what will happen?

Accepted Answer

$$Q_c = 0.25$$, reaction shifts right.

Question 7

Which of the following best explains why $$Q_c$$ can be any value, but $$K_c is $$constant at a given temperature?

Accepted Answer

$$Q_c$$ depends on the current concentrations, while $$K_c$$ depends only on temperature.

Question 8

If a reaction mixture is disturbed so that $$Q_c \u003c K_c$$, what will happen to the concentrations of products and reactants as the system returns to equilibrium?

Accepted Answer

Product concentrations will increase and reactant concentrations will decrease.

Question 9

A reaction at equilibrium is disturbed by adding more reactant. What happens to $$Q_c$$ and how does the system respond?

Accepted Answer

$$Q_c$$ decreases and the reaction shifts right to form more products.

Question 10

In a closed system, the reaction $$A \rightleftharpoons B$$ has $$K_c = 5.0. If$$ $$[A] = 0.2 M $$and $$[B] = 1.0 M$$, what is $$Q_c$$ and what will happen?

Accepted Answer

$$Q_c = 5.0$$, system is at equilibrium.

Chemistry: Chapter 15 lecture notes part 2

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