Chapter 21, Problem 99A

Interpretation Introduction

Interpretation: The equilibrium constant expression for the decomposition of ammonia to nitrogen and hydrogen needs to be given.

Concept Introduction: For a general equilibrium reaction as follows:

  $aA+bB\rightleftharpoons cC+dD$

The equilibrium constant expression can be represented as follows:

  $K=\frac{{\left[\text{C}\right]}^c{\left[\text{D}\right]}^d}{{\left[\text{A}\right]}^a{\left[\text{B}\right]}^b}$

Explanation of Solution

The decomposition of ammonia to nitrogen and hydrogen is represented as follows:

  $2{\text{NH}}_3\left(g\right)\rightleftharpoons {\text{N}}_2\left(g\right)+{\text{3H}}_{\text{2}}\left(g\right)$

Here, the expression for the equilibrium constant is written in such a way that equilibrium concentrations of product side species are taken in the numerator and equilibrium concentrations of reactant side species are taken in the denominator.

Here, the stochiometric coefficient for any reactant or product species is represented as the power of its equilibrium concentration.

Thus, the equilibrium constant expression is represented as follows:

  $K=\frac{\left[{\text{N}}_2\right]{\left[{\text{H}}_{\text{2}}\right]}^3}{{\left[{\text{NH}}_3\right]}^2}$

Here, $K$ is the equilibrium constant, and given concentration of reactant and product species are equilibrium concentrations.