Hydrolysis
Highly charged metal ions (> +3) cause pH shifts due to hydrolysis:
Fe(H2O)63+ + H2O ? Fe(H2O)5OH2+ + H3O+
Many other salts also cause pH shifts when dissolved in water. These salts contain the conjugate acid or base of a weak base or acid.
NH4Cl: NH4+ + H2O ? NH3 + H3O+ pHɟ
NaCH3CO2: CH3CO2- + H2O ? CH3CO2H + OH - pHɳ
These reactions are called hydrolysis.