Question 1

Which of the following best describes a chemical equilibrium according to the study materials?

Accepted Answer

A dynamic state where the rates of the forward and reverse reactions are equal and the concentrations of reactants and products remain constant over time.

Question 2

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

Accepted Answer

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

Question 3

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

Accepted Answer

The value of $$K is $$always the same for a given reaction at a specific temperature.

Question 4

For the reaction $$CaCO_3(s$$) \rightleftharpoons CaO(s) + $$CO_2(g$$)$$, which of the following is the correct equilibrium constant expression?

Accepted Answer

$$K = P_{CO_2$}$$

Question 5

If the equilibrium constant $$K$$ for a reaction is much less than 1, what does this indicate about the position of equilibrium?

Accepted Answer

The reaction favors the formation of reactants.

Question 6

Given the reaction $$2NO_2(g) \rightleftharpoons N_2O_4(g)$$ with $$K_p = 0.40 at a $$certain temperature, what is the value of $$K_p$$ for the reverse reaction?

Accepted Answer

$$K_p = 1/0.40 = 2.5$$

Question 7

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 8

For the reaction $$3O_2(g) \rightleftharpoons 2O_3(g)$$, how will increasing the pressure affect the position of equilibrium?

Accepted Answer

The equilibrium will shift toward the side with fewer moles of gas.

Question 9

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

Accepted Answer

The reaction will proceed in the forward direction to form more products.

Question 10

According to Le Chatelier's principle, what will happen if the temperature is increased for an endothermic reaction at equilibrium?

Accepted Answer

The equilibrium will shift toward the products.

Question 11

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

Accepted Answer

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

Question 12

For the reaction $$N_2O_4(g) \rightleftharpoons 2NO_2(g)$$, what will happen if the volume of the container is decreased?

Accepted Answer

The equilibrium will shift toward the side with fewer moles of gas.

Question 13

Which of the following is true about the equilibrium constant expression for a reaction involving a pure solid or liquid?

Accepted Answer

The concentration of a pure solid or liquid is omitted from the equilibrium expression.

Question 14

A reaction mixture initially contains only reactants. As the reaction proceeds, $$Q$$ increases until it equals $$K. $$What does this indicate?

Accepted Answer

The reaction is moving toward equilibrium and will stop when $$Q = K.$$

Question 15

For the reaction $$A(g) + B(g) \rightleftharpoons 2C(g)$$, the equilibrium concentrations are $$[A] = 0.10 M$$, $$[B] = 0.20 M$$, and $$[C] = 0.30 M. $$What is the value of $$K$$?

Accepted Answer

$$K = \frac{[C]^2}{[A][B]} = \frac{(0.30)^2$}{0.10 	imes 0.20}$$

Question 16

Which of the following changes will shift the equilibrium position of an exothermic reaction to the left?

Accepted Answer

Increasing the temperature.

Question 17

If the equilibrium constant $$K$$ for a reaction is $$1.5 	imes 10^5$, what can you conclude about the reaction at equilibrium?

Accepted Answer

The reaction favors the formation of products.

Question 18

For the reaction $$2NO_2(g) \rightleftharpoons N_2O_4(g)$$, what will happen if more $$NO_2 is $$added to the system at equilibrium?

Accepted Answer

The equilibrium will shift to produce more $$N_2O_4.$$

L'équilibre chimique (Chemical Equilibrium): Concepts, Calculations, and Applications

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