Steps for determining acidity or basicity of a salt by hydrolysis:
- Write the neutralization reaction in reverse (salt and water makes base and acid).
- Break up the salt into its ions.
- To write the base, add an $\ce{OH-}$ to the cation (the positive ion) for each + charge.
- To write the acid, Add $\ce{H+}$ to the anion (the negative ion) for each negative charge.
If you for a strong base, the salt is basic. $\ce{(NaOH, KOH, LiOH, Mg(OH)_2, ...)}$
If you form a strong acid it is acidic. $\ce{(HCl, HNO_3, HClO_4, HBr,...)}$
If you form both a strong acid and a strong base it is neutral.
EXAMPLE:
$\ce{NH_4Cl}$
$\ce{NH4Cl + H_2O <=> NH4OH + HCl}$
Since $\ce{HCl}$ is a strong acid it breaks up and yields $\ce{H+}$, the salt is acidic.