Chapter 12, Problem 29QRT

(a)

Interpretation Introduction

Interpretation:

The equilibrium constant expression, ${\text{K}}_{\text{P}}$ for the reaction ${\text{N}}_{\text{2(g)}}{\text{ + 2O}}_{\text{2(g)}}\rightleftharpoons {\text{ N}}_{\text{2}}{\text{O}}_{\text{4}}{}_{\text{(g)}}$ has to be written.

Concept Introduction:

Equilibrium constant$\left({\text{K}}_{\text{p}}\right)$:

In gas phase reactions, partial pressure is used to write equilibrium equation than molar concentration.  Equilibrium constant $\left({\text{K}}_{\text{p}}\right)$ is defined as ratio of partial pressure of products to partial pressure of reactants.  Each partial pressure term is raised to a power, which is same as the coefficients in the chemical reaction

Consider the reaction where A reacts to give B.

    $\text{aA}\rightleftharpoons \text{bB}$

    $\begin{array}{l}\text{Rate of forward reaction = Rate of reverse reaction}\\ {\text{k}}_{\text{f}}{\text{P}}_{\text{A}}{}^{\text{a}}{\text{=k}}_{\text{r}}{\text{P}}_{\text{B}}{}^{\text{a}}\end{array}$

On rearranging,

    $\frac{{\text{P}}_{\text{B}}{}^{\text{b}}}{{\text{P}}_{\text{A}}{}^{\text{a}}}\text{=}\frac{{\text{k}}_{\text{f}}}{{\text{k}}_{\text{r}}}{\text{=K}}_{\text{p}}$

Where,

    ${\text{k}}_{\text{f}}$ is the rate constant of the forward reaction.

    ${\text{k}}_{\text{r}}$ is the rate constant of the reverse reaction.

    ${\text{K}}_{\text{p}}$ is the equilibrium constant.

The concentration of solids and pure liquids do not change, so their concentration terms are not included in the equilibrium constant expression.

(b)

Interpretation Introduction

Interpretation:

The equilibrium constant expression, ${\text{K}}_{\text{P}}$ for the reaction ${\text{SiH}}_4{}_{\text{(g)}}{\text{ + 2O}}_{\text{2}}{}_{\text{(g)}}\rightleftharpoons {\text{SiO}}_{\text{2(s)}}{\text{ + 2H}}_{\text{2}}{\text{O}}_{\text{(g)}}$ has to be written.

Concept Introduction:

Refer part (a) for concept.

(c)

Interpretation Introduction

Interpretation:

The equilibrium constant expression, ${\text{K}}_{\text{P}}$ for the reaction ${\text{MgO}}_{\text{(s)}}{\text{ + SO}}_{\text{2(g)}}\text{ + }\frac{1}{2}{\text{O}}_{\text{2(g)}}\rightleftharpoons {\text{ MgSO}}_{\text{4(s)}}$ has to be written.

Concept Introduction:

Refer part (a) for concept.

(d)

Interpretation Introduction

Interpretation:

The equilibrium constant expression, ${\text{K}}_{\text{P}}$ for the reaction ${\text{2PbS}}_{\text{(s)}}{\text{ + 3O}}_{\text{2(g)}}\rightleftharpoons {\text{ 2PbO}}_{\text{(s)}}{\text{ + 2SO}}_{\text{2(g)}}$ has to be written.

Concept Introduction:

Refer part (a) for concept.