Quiz 2 - Chemical Equilibrium | Chemical Equilibrium

General Chemistry 2 - Quiz 2 - Chemical Equilibrium

1

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

According to Le Châtelier's principle, if a dynamic equilibrium is disturbed by changing the conditions, the equilibrium position moves to counteract the change. The quantities whose change may affect an equilibrium are the concentration of a reactant or product, the volume, the pressure and the temperature

Le Châtelier’s Principle The Equilibrium Constant
2

Which of the following is true for a system at equilibrium?

At equilibrium, the forward and reverse reaction rates are equal, but the concentrations of reactants and products may not be the same. The system is dynamic, with reactions continuing to occur in both directions.

The Concept of Equilibrium
3

For the reaction H2​ (g) + I2 (g) ⇌ 2 HI (g), what happens to the equilibrium position when additional H2​ is added?

According to Le Châtelier’s principle, adding more H2​ (a reactant) will shift the equilibrium to the right, toward the formation of more products to re-establish equilibrium.

Le Châtelier’s Principle Effect of Concentration Changes
4

What is the equilibrium constant expression Kc of the reaction: 2 ICl (s) ⇌ I2 (s) + Cl2 (g)?

Equilibrium constant KC: ratio of product concentrations to reactant concentrations at the equilibrium
Pure solids reactants and products do not appear in the equilibrium-constant expression (= 1 by convention)

The Equilibrium Constant Equilibrium Expressions
5

How can we increase the total amount of produced Cl2 during the reaction: 2 ICl (s)  I2 (s) + Cl2 (g)?

According to Le Châtelier’s principle, removing a product from the equilibrium system will shift the equilibrium to the right, producing more Cl2 to replace what was removed, thus increasing the total amount of Cl2 produced. Adding more ICl might seem like it would increase the production of Cl2. However, because ICl is a solid, adding more of it does not affect the equilibrium position.

Le Châtelier’s Principle Equilibrium Expressions
6

What happens when the reaction quotient Qc is less than the equilibrium constant K?

Reaction quotient QC: ratio of product concentrations to reactant concentrations at a given time
If QC < K, the reaction will move to the right ⇒ net formation of product

Using Equilibrium Expressions
7

Which of the following will shift the equilibrium of the reaction N2 ​(g) + 3 H2 (g) ⇌ 2 NH3 ​(g) to the right?

Increasing the pressure favors the side of the reaction with fewer moles of gas. Since the forward reaction produces fewer moles of gas (2 moles of NH3 vs. 4 moles of reactants), increasing the pressure shifts the equilibrium to the right.

Le Châtelier’s Principle Effect of Pressure and Volume Changes
8

What is the effect of increasing the concentration of a reactant on the equilibrium constant (Kc) of a reaction?

The equilibrium constant (Kc​) is dependent only on temperature and not on changes in concentration, pressure, or volume. Increasing the concentration shifts the equilibrium position but does not affect Kc​.

The Equilibrium Constant
9

Given the reaction A ⇌ 2 B, if Kc = 4.0, which statement is true?

Since Kc > 1, the equilibrium favors the products, meaning the concentration of B is greater than that of A.

Using Equilibrium Expressions
10

What is the value of Kc​ for the reverse reaction if the equilibrium constant for the forward reaction is 1.5 x 103?

If a reaction is reversed, the equilibrium constant for the reverse reaction is the reciprocal of the original equilibrium constant:

K'c = 1Kc

K'c = equilibrium constant of the reversed reaction
Kc = equilibrium constant of the original reaction

 

So K'c = 11.5 × 103 = 6.7 x 10-4

Equilibrium Expressions