Question

Ammonia is produced by the Haber process, in which nitrogen and hydrogen are reacted directly using an iron mesh impregnated with oxides as a catalyst. For the reaction ${\mathbf{\text{N}}}_{\mathbf{2}}\mathbf{\left(}\mathit{g}\mathbf{\right)}\mathbf{+}\mathbf{3}{\mathbf{\text{H}}}_{\mathbf{2}}\mathbf{\left(}\mathit{g}\mathbf{\right)}\mathbf{\rightleftharpoons }\mathbf{2}{\mathbf{\text{NH}}}_{\mathbf{3}}\mathbf{\left(}\mathit{g}\mathbf{\right)}$

equilibrium constants ( ${\mathit{K}}_{\mathbf{s}\mathbf{p}}$values) as a function of temperature are

_{$$\begin{gathered} {\mathbf{300}}^{\mathbf{°}}\mathit{C}\mathbf{,}\mathbf{}\mathbf{4}\mathbf{.}\mathbf{34}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{3}} \\ {\mathbf{500}}^{\mathbf{°}}\mathit{C}\mathbf{,}\mathbf{}\mathbf{1}\mathbf{.}\mathbf{45}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{5}} \\ {\mathbf{600}}^{\mathbf{°}}\mathit{C}\mathbf{,}\mathbf{}\mathbf{2}\mathbf{.}\mathbf{5}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{6}} \end{gathered}$$}

Is the reaction exothermic or endothermic?

Short answer

The given reaction will be exothermic.

Step-by-step solution

Equilibrium constant expression

Equilibrium constant expression describes the relationship between reactants and products in a reaction that is in equilibrium with respect to some unit.

The ratio of the concentrations of a reaction at equilibrium is the equilibrium constant expression.

The equilibrium constant_{$\left(K\right)$}is a constant value that appears in every equilibrium constant equation.

_{$\mathit{K}\mathbf{=}\frac{\mathbf{\text{concentration of products}}}{\mathbf{\text{concentration of reactants}}}$}

In the exothermic reactions, an increase in temperature decreases the equilibrium constant K whereas, in endothermic reactions, an increase in temperature increases K.

Determine the type of the reaction

The balanced chemical reaction equation is as follows:

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

The equilibrium constant expression for this reaction is as follows:

$K=\frac{{\left[N{H}_3\right]}^2}{\left[N_2\right]{\left[H_2\right]}^3}$

From the given data, it can be seen that the value of the equilibrium constant decreases with an increase in temperature.

According to Le Chatelier's principle, adding heat to a reactionfavorsthe endothermic direction since itminimizesthe quantity of heat produced in the system.

The$K$ value decreases with temperature.

Hence, it can be concluded that this reaction is Exothermic.