Ammonium chloride ($N{H}_{4}Cl$) is a salt formed from a Weak Base ($N{H}_3$) and a Strong Acid ($HCl$).

• In water, it dissociates: $N{H}_{4}Cl\to N{H}_4^{+}+C{l}^{-}$.
• The $C{l}^{-}$ ion is the spectator ion (from strong acid).
• The $N{H}_4^{+}$ ion (conjugate acid of weak base) reacts with water (Cationic Hydrolysis): $N{H}_4^{+}+H_{2}O\rightleftharpoons N{H}_{4}OH+H^{+}$
• The liberation of $H^{+}$ ions makes the solution acidic ($pH<7$).