Chapter 7.4, Problem 7.11PP

(a)

Interpretation Introduction

Interpretation:

Addition of $\text{Pb}(s)$ in the given equilibrium reaction results in increase, decrease, or no change in the volume of hydrogen gas has to be predicted.

    $382\text{cal}+\text{Pb}(s)+{\text{2H}}^{+}(aq)\rightleftharpoons {\text{Pb}}^{2+}(aq)+{\text{H}}_{\text{2}}(g)$

Concept Introduction:

LeChatelier’s principle states that if a stress is applied on the system that is present at equilibrium, then the system will respond to the stress applied by altering the composition at equilibrium in a way to minimize the stress that is applied.

Explanation of Solution

Given equilibrium reaction is,

    $382\text{cal}+\text{Pb}(s)+{\text{2H}}^{+}(aq)\rightleftharpoons {\text{Pb}}^{2+}(aq)+{\text{H}}_{\text{2}}(g)$

On addition of $\text{Pb}(s)$, there will not be any change in the equilibrium because the added reactant is a solid.  As the substance added is a solid, addition or removal of solid substance does not have any effect on the volume of hydrogen gas.  Therefore, the volume of hydrogen gas remains the same.

(b)

Interpretation Introduction

Interpretation:

Addition of ${\text{Pb}}^{2+}$ ions in the given equilibrium reaction results in increase, decrease, or no change in the volume of hydrogen gas has to be predicted.

    $382\text{cal}+\text{Pb}(s)+{\text{2H}}^{+}(aq)\rightleftharpoons {\text{Pb}}^{2+}(aq)+{\text{H}}_{\text{2}}(g)$

Concept Introduction:

Refer part (a).

Explanation of Solution

Given equilibrium reaction is,

    $382\text{cal}+\text{Pb}(s)+{\text{2H}}^{+}(aq)\rightleftharpoons {\text{Pb}}^{2+}(aq)+{\text{H}}_{\text{2}}(g)$

On addition of ${\text{Pb}}^{2+}(aq)$ ions, the concentration of the product is increased.  To counter balance the equilibrium is shifted towards the reactant formation.  This results in decrease in the volume of hydrogen gas.

(c)

Interpretation Introduction

Interpretation:

Removal of ${\text{H}}^{+}$ ions in the given equilibrium reaction results in increase, decrease, or no change in the volume of hydrogen gas has to be predicted.

    $382\text{cal}+\text{Pb}(s)+{\text{2H}}^{+}(aq)\rightleftharpoons {\text{Pb}}^{2+}(aq)+{\text{H}}_{\text{2}}(g)$

Concept Introduction:

Refer part (a).

Explanation of Solution

Given equilibrium reaction is,

    $382\text{cal}+\text{Pb}(s)+{\text{2H}}^{+}(aq)\rightleftharpoons {\text{Pb}}^{2+}(aq)+{\text{H}}_{\text{2}}(g)$

On removal of ${\text{H}}^{+}(aq)$ ions, the concentration of the reactant is decreased.  To counter balance the equilibrium is shifted towards the reactant formation.  This results in decrease in the volume of hydrogen gas.

(d)

Interpretation Introduction

Interpretation:

Reducing the temperature in the given equilibrium reaction results in increase, decrease, or no change in the volume of hydrogen gas has to be predicted.

    $382\text{cal}+\text{Pb}(s)+{\text{2H}}^{+}(aq)\rightleftharpoons {\text{Pb}}^{2+}(aq)+{\text{H}}_{\text{2}}(g)$

Concept Introduction:

Refer part (a).

Explanation of Solution

Given equilibrium reaction is,

    $382\text{cal}+\text{Pb}(s)+{\text{2H}}^{+}(aq)\rightleftharpoons {\text{Pb}}^{2+}(aq)+{\text{H}}_{\text{2}}(g)$

The reaction given above is an endothermic reaction.  Lowering the temperature of the equilibrium reaction results in removal of heat energy in the reactant side.  This makes the equilibrium to shift towards the reactant side resulting in decrease of the volume of hydrogen gas.

(e)

Interpretation Introduction

Interpretation:

Addition of catalyst in the given equilibrium reaction results in increase, decrease, or no change in the volume of hydrogen gas has to be predicted.

    $382\text{cal}+\text{Pb}(s)+{\text{2H}}^{+}(aq)\rightleftharpoons {\text{Pb}}^{2+}(aq)+{\text{H}}_{\text{2}}(g)$

Concept Introduction:

Refer part (a).

Explanation of Solution

Given equilibrium reaction is,

    $382\text{cal}+\text{Pb}(s)+{\text{2H}}^{+}(aq)\rightleftharpoons {\text{Pb}}^{2+}(aq)+{\text{H}}_{\text{2}}(g)$

In case of an equilibrium reaction, addition of catalyst does not have any effect on the concentration of the products or the reactants.  This is because, the catalyst increase the rate of the forward reaction as well as the reverse reaction.  Therefore, the volume of hydrogen gas do not change on addition of catalyst.