Chapter 6, Problem 71P

Consider the exothermic reaction: ${\text{C}}_{{}^{\text{2}}}{\text{H}}_4(g)+{\text{ CI}}_{\text{2}}(g)\stackrel{}{\rightleftarrows }{\text{ C}}_{{}^{\text{2}}}{\text{H}}_4{\text{CI}}_2(g).$ What effect does each of the following changes have on the direction of equilibrium?
a. increase ${\text{[C}}_2{\text{H}}_4\text{]}$
b. decrease ${\text{[CI}}_2]$
c. decrease ${\text{[C}}_2{\text{H}}_4{\text{CI}}_2\text{]}$
d. decrease pressure
e. increase temperature
f. decrease temperature

Interpretation Introduction

(a)

Interpretation:

The effect of increasing [C₂H₄] on the direction of the equilibrium on the following exothermic reaction should be determined.

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

Concept Introduction:

The Le Chatelier's principle states that if a change in temperature, pressure or concentration is applied on a system which is in equilibrium, the equilibrium shifts in order to counteract that change.

Answer to Problem 71P

Equilibrium will shift to right.

Explanation of Solution

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

According to the Le Chatelier's principle, adding more amount of reactant or removing product will shift the equilibrium to the right and removing reactant or adding more amount of product will shift the equilibrium to the left. So, when [C₂H₄] increases, equilibrium will shift in a direction at which [C₂H₄] decreases. Thus, the equilibrium will shift to right.

Interpretation Introduction

(b)

Interpretation:

The effect of decreasing [Cl₂] on the direction of the equilibrium on the following exothermic reaction should be determined.

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

Concept Introduction:

The Le Chatelier's principle states that if a change in temperature, pressure of concentration is applied on a system which is in equilibrium, the equilibrium shifts in order to counteract that change.

Answer to Problem 71P

Equilibrium will shift to left.

Explanation of Solution

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

According to the Le Chatelier's principle, adding more amount of reactant or removing product will shift the equilibrium to the right and removing reactant or adding more amount of product will shift the equilibrium to the left. So, when [Cl₂] is decreased, equilibrium will shift in a direction at which [Cl₂] increases. Thus, the equilibrium will shift to left.

Interpretation Introduction

(c)

Interpretation:

The effect of decreasing [C₂H₄Cl₂] on the direction of the equilibrium on the following exothermic reaction should be determined.

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

Concept Introduction:

The Le Chatelier's principle states that if a change in temperature, pressure of concentration is applied on a system which is in equilibrium, the equilibrium shifts in order to counteract that change.

Answer to Problem 71P

Equilibrium will shift to right.

Explanation of Solution

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

According to the Le Chatelier's principle, adding more amount of reactant or removing product will shift the equilibrium to the right and removing reactant and adding more amount of product will shift the equilibrium to the left. So, when [C₂H₄Cl₂] is decreased, equilibrium will shift in a direction at which [C₂H₄Cl₂] increases. Thus, the equilibrium will shift to the right.

Interpretation Introduction

(d)

Interpretation:

The effect of decreasing pressure on the direction of the equilibrium on the following exothermic reaction should be determined.

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

Concept Introduction:

The Le Chatelier's principle states that if a change in temperature, pressure of concentration is applied on a system which is in equilibrium, the equilibrium shifts in order to counteract that change.

Answer to Problem 71P

Equilibrium will shift to left.

Explanation of Solution

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

In above reaction, number of moles of reactants is two and number of moles of product is one. When pressure decreases, the equilibrium shifts in the direction where more number of moles are present in the system to increase the pressure. So, in this case the equilibrium will shift to left.

Interpretation Introduction

(e)

Interpretation:

The effect of increasing temperature on the direction of the equilibrium on the following exothermic reaction should be determined.

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

Concept Introduction:

The Le Chatelier's principle states that if there is a change in temperature, pressure of concentration is applied on a system which is in equilibrium, the equilibrium shifts in order to counteract that change.

Answer to Problem 71P

Equilibrium will shift to left.

Explanation of Solution

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

The forward reaction is an exothermic reaction. So, the exothermic reaction release heat during the reaction. When temperature increases, reaction that removes heat is favored. In this case when temperature increases, the backward reaction is favored. Hence, the equilibrium will shift to the left.

Interpretation Introduction

(f)

Interpretation:

The effect of decreasing temperature on the direction of the equilibrium on the following exothermic reaction should be determined.

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

Concept Introduction:

The Le Chatelier's principle states that if a change in temperature, pressure of concentration is applied on a system which is in equilibrium, the equilibrium shifts in order to counteract that change.

Answer to Problem 71P

Equilibrium will shift to right.

Explanation of Solution

  ${\text{C}}_2{\text{H}}_4{\text{(g) + Cl}}_2\text{(g) }\rightleftharpoons {\text{ C}}_2{\text{H}}_4{\text{Cl}}_2\text{(g)}$

The forward reaction is an exothermic reaction. So, exothermic reaction release heat during the reaction. When temperature decreases, reaction that adds heat is favored. In this case when temperature decreases, the forward reaction is favored. Hence, the equilibrium will shift to right.