Chapter 17, Problem 17.27P

(a)

Interpretation Introduction

Interpretation:

${\text{K}}_{\text{p}}$ and ${\text{K}}_{\text{c}}$ has to be compared when more moles of products and less moles of reactants are present in the system.

Concept Introduction:

The equilibrium constant in terms of concentration ${\text{K}}_{\text{c}}$ and in terms of partial pressure ${\text{K}}_{\text{p}}$ are related by an equation given below.

${\text{K}}_{\text{p}}{\text{ = K}}_{\text{c}}{\left(\text{RT}\right)}^{{\text{Δn}}_{\text{gas}}}$

Where,

    $\begin{array}{l}{\text{K}}_{\text{p}}\text{= equilibrium constant in terms of pressure}\\ {\text{K}}_{\text{c}}\text{= equilibrium constant in terms of concentration}\\ {\text{Δn}}_{\text{gas}}\text{= number of moles gaseous products - number of moles gaseous reactants}\\ \text{R = universal gas constant}\end{array}$

When number of moles of gaseous product equals to number of moles of gaseous reactants then ${\text{Δn}}_{\text{gas}}$ will become zero. Hence, ${\text{K}}_{\text{p}}$ will be equal to ${\text{K}}_{\text{c}}.$

All other cases when number of gas molecules of reactant and product are different ${\text{K}}_{\text{p}}$ and ${\text{K}}_{\text{c}}$ will be having different values.

(b)

Interpretation Introduction

Interpretation:

Relative size of ${\text{K}}_{\text{p}}$ and ${\text{K}}_{\text{c}}$ for any gaseous equilibrium has to be compared.

Concept Introduction: