Chapter 18, Problem 97A

(a)

Interpretation Introduction

Interpretation: The effect of adding more ${\text{H}}_{\text{2}}$ on the equilibrium concentration of ${\text{H}}_{\text{2}}\text{O}$ for the reaction ${\text{Fe}}_{\text{3}}{\text{O}}_4\left(s\right)+4{\text{H}}_2\left(g\right)\rightleftharpoons 3\text{Fe}\left(s\right)+4{\text{H}}_{\text{2}}\text{O}\left(g\right)$ is to be determined.

Concept Introduction: According to Le Chatelier's Principle, an equilibrium system will release stress when it is subjected to stress.

Answer to Problem 97A

Adding more ${\text{H}}_{\text{2}}$ will increases the equilibrium concentration of ${\text{H}}_{\text{2}}\text{O}$ .

Explanation of Solution

The reaction is as follows:

  ${\text{Fe}}_{\text{3}}{\text{O}}_4\left(s\right)+4{\text{H}}_2\left(g\right)\rightleftharpoons 3\text{Fe}\left(s\right)+4{\text{H}}_{\text{2}}\text{O}\left(g\right)$

When a solid ${\text{Fe}}_{\text{3}}{\text{O}}_4$ reacts with ${\text{H}}_2$ gas, it will give solid $\text{Fe}$ and water vapor. If more ${\text{H}}_2$ is added to a system at equilibrium, the system will shift to the right to remove the excess hydrogen. Adding extra hydrogen to the mixture would increase the concentration of ${\text{H}}_{\text{2}}\text{O}$ at equilibrium.

(b)

Interpretation Introduction

Interpretation: The effect of increasing the pressure on the equilibrium concentration of ${\text{H}}_{\text{2}}\text{O}$ for the reaction ${\text{Fe}}_{\text{3}}{\text{O}}_4\left(s\right)+4{\text{H}}_2\left(g\right)\rightleftharpoons 3\text{Fe}\left(s\right)+4{\text{H}}_{\text{2}}\text{O}\left(g\right)$ is to be determined.

Concept Introduction: According to Le Chatelier's Principle, an equilibrium system will release stress when it is subjected to stress.

Answer to Problem 97A

Increasing the pressure will not affect the equilibrium concentration of ${\text{H}}_{\text{2}}\text{O}$ .

Explanation of Solution

The reaction is as follows:

  ${\text{Fe}}_{\text{3}}{\text{O}}_4\left(s\right)+4{\text{H}}_2\left(g\right)\rightleftharpoons 3\text{Fe}\left(s\right)+4{\text{H}}_{\text{2}}\text{O}\left(g\right)$

Le Chatelier's Principle states that the equilibrium will move toward the side of the reaction with fewer gas molecules as pressure increases.

When a solid ${\text{Fe}}_{\text{3}}{\text{O}}_4$ reacts with ${\text{H}}_2$ gas, it will give solid $\text{Fe}$ and water vapor. In the reaction, the left side has four gaseous molecules of hydrogen, and the right side has four gaseous molecules of water vapor. The number of gaseous molecules is equal on both sides. Hence any change in pressure will not affect the equilibrium concentration of ${\text{H}}_{\text{2}}\text{O}$ .

(c)

Interpretation Introduction

Interpretation: The effect of removing ${\text{H}}_{\text{2}}$ on the equilibrium concentration of ${\text{H}}_{\text{2}}\text{O}$ for the reaction ${\text{Fe}}_{\text{3}}{\text{O}}_4\left(s\right)+4{\text{H}}_2\left(g\right)\rightleftharpoons 3\text{Fe}\left(s\right)+4{\text{H}}_{\text{2}}\text{O}\left(g\right)$ is to be determined.

Concept Introduction: According to Le Chatelier's Principle, an equilibrium system will release stress when it is subjected to stress.

Answer to Problem 97A

Removing ${\text{H}}_{\text{2}}$ will decreases the equilibrium concentration of ${\text{H}}_{\text{2}}\text{O}$ .

Explanation of Solution

The reaction is as follows:

  ${\text{Fe}}_{\text{3}}{\text{O}}_4\left(s\right)+4{\text{H}}_2\left(g\right)\rightleftharpoons 3\text{Fe}\left(s\right)+4{\text{H}}_{\text{2}}\text{O}\left(g\right)$

When a solid ${\text{Fe}}_{\text{3}}{\text{O}}_4$ reacts with ${\text{H}}_2$ gas, it will give solid $\text{Fe}$ and water vapor. If ${\text{H}}_2$ is removed to a system at equilibrium, the system will shift to the left to produce hydrogen. Removing hydrogen from the mixture would decrease the concentration of ${\text{H}}_{\text{2}}\text{O}$ at equilibrium.

(d)

Interpretation Introduction

Interpretation: The effect of adding a catalyst on the equilibrium concentration of ${\text{H}}_{\text{2}}\text{O}$ for the reaction ${\text{Fe}}_{\text{3}}{\text{O}}_4\left(s\right)+4{\text{H}}_2\left(g\right)\rightleftharpoons 3\text{Fe}\left(s\right)+4{\text{H}}_{\text{2}}\text{O}\left(g\right)$ is to be determined.

Concept Introduction: According to Le Chatelier's Principle, an equilibrium system will release stress when it is subjected to stress.

Answer to Problem 97A

The catalyst no affects the equilibrium concentration of ${\text{H}}_{\text{2}}\text{O}$ .

Explanation of Solution

The reaction is as follows:

  ${\text{Fe}}_{\text{3}}{\text{O}}_4\left(s\right)+4{\text{H}}_2\left(g\right)\rightleftharpoons 3\text{Fe}\left(s\right)+4{\text{H}}_{\text{2}}\text{O}\left(g\right)$

When a reaction is already in equilibrium, adding a catalyst to the mixture does not influence the equilibrium concentration ${\text{H}}_{\text{2}}\text{O}$ .