Hydrolysis constant of salt derived from strong acid and weak base is 2 × 10–5. The dissociation constant of the weak base is

NH4Cl is a salt of strong acid and weak base.NH4Cl⟶H2ONH4+(aq)+Cl-(aq)NH4+(aq) will not undergo hydrolysisNH4++H2O⇌NH4OH+H3O+Kh=KaNH4+=KwKbNH4OH⇒2×10-5=10-14KbNH4OH⇒KbNH4OH=5×10-10