Explain the effect of increase in pressure on the equilibrium: 3H2(g) <=> 2NH3(g) (ΔH= -92KJ/mol)

Question 6

a) Write the word equation for the reaction.

$$\text{Ammonium chloride} \rightleftharpoons \text{Ammonia} + \text{Hydrogen chloride}$$

b) Write a complete balanced equation for the forward reaction.

$$\ce{NH4Cl(s) -> NH3(g) + HCl(g)}$$

c) Write the balanced equation for the reverse reaction.

$$\ce{NH3(g) + HCl(g) -> NH4Cl(s)}$$

d) Draw an energy change for the forward and backward reaction. In your graph label the activation energy (Ea) and the heat of reaction ($\Delta H$).

The decomposition of ammonium chloride by heating is an endothermic process. Therefore, the forward reaction absorbs energy, and the products have higher energy than the reactants. The reverse reaction is exothermic.

Forward reaction

$$\ce{NH4Cl(s) -> NH3(g) + HCl(g)}$$

This is an endothermic reaction.

\begin{tikzpicture}[scale=0.8] % Axes \draw[->] (0,0) -- (6,0) node[right] {Reaction Progress}; \draw[->] (0,0) -- (0,5) node[above] {Potential Energy}; % Reactants \draw[thick] (0.5,1) -- (1.5,1) node[left,yshift=-0.5cm] {$\ce{NH4Cl(s)}$}; % Products \draw[thick] (4.5,4) -- (5.5,4) node[right,yshift=0.5cm] {$\ce{NH3(g) + HCl(g)}$}; % Reaction path \draw[thick] (1.5,1) .. controls (2.5,4.5) and (3.5,4.5) .. (4.5,4); % Activation Energy (Ea) \draw[<->] (1.7,1) -- (1.7,4.5); \node at (2.2,2.75) {$\mathrm{E_{a,f}}$}; % Heat of Reaction (ΔH) \draw[<->] (5.7,1) -- (5.7,4); \node at (6.2,2.5) {$\Delta H_f$}; \end{tikzpicture}

Backward reaction

$$\ce{NH3(g) + HCl(g) -> NH4Cl(s)}$$

This is an exothermic reaction.

\begin{tikzpicture}[scale=0.8] % Axes \draw[->] (0,0) -- (6,0) node[right] {Reaction Progress}; \draw[->] (0,0) -- (0,5) node[above] {Potential Energy}; % Reactants \draw[thick] (0.5,4) -- (1.5,4) node[left,yshift=-0.5cm] {$\ce{NH3(g) + HCl(g)}$}; % Products \draw[thick] (4.5,1) -- (5.5,1) node[right,yshift=0.5cm] {$\ce{NH4Cl(s)}$}; % Reaction path \draw[thick] (1.5,4) .. controls (2.5,4.5) and (3.5,4.5) .. (4.5,1); % Activation Energy (Ea) \draw[<->] (1.7,4) -- (1.7,4.5); \node at (2.2,4.25) {$\mathrm{E_{a,r}}$}; % Heat of Reaction (ΔH) \draw[<->] (5.7,1) -- (5.7,4); \node at (6.2,2.5) {$\Delta H_r$}; \end{tikzpicture}