Question

Equilibrium constants $\left(K_p\right)$ for the reaction $\frac{3}{2}{H}_2\left(g\right)+\frac{1}{2}{N}_2\left(g\right)\rightleftharpoons N{H}_3\left(g\right)$ are $0.0266$ and $0.0129$ at ${350}^{\circ }C$ and ${400}^{\circ }C$ respectively. Calculate the heat of formation of gaseous ammonia.

Answer 1

$3/2H_2+\frac{1}{2}{N}_2\rightleftharpoons {NH}_3$

$K_{{350}^0}=0.0266$

$K_{{400}^0}=0.0129$

We know $In\left(\frac{K_2}{K_1}\right)=\frac{-\Delta H}{R}[\frac{1}{T_2}-\frac{1}{T_1}]$

$In\left(\frac{0.0266}{0.0129}\right)=-\left(\frac{\Delta H}{8.314}\right)[\frac{1}{623}-\frac{1}{673}]$

$\Delta H=-50453J$

$=-50.453KJ$