5.19C - Ammonia and the reversible Haber reaction

Making ammonia reversibly

The Haber process makes ammonia from nitrogen and hydrogen. The reactants are nitrogen and hydrogen; the product is ammonia.

nitrogen + hydrogen ⇌ ammonia

A reversible reaction can occur in both directions: the products can react to reform the original reactants. The forward Haber reaction makes ammonia. The reverse reaction breaks ammonia down into nitrogen and hydrogen.

The reversible arrow, ⇌, shows that both directions are possible. It does not mean the reaction has stopped, and it does not mean there must be equal amounts of every substance.

The balanced equation

Nitrogen and hydrogen occur as diatomic molecules, $\mathrm{N_2}$ and $\mathrm{H_2}$. Ammonia has the formula $\mathrm{NH_3}$.

The state symbol (g) means gas. One nitrogen molecule reacts with three hydrogen molecules to form two ammonia molecules. There are two nitrogen atoms and six hydrogen atoms on each side, so atoms are conserved. The reverse reaction uses the same ratio in reverse.