a) \(Fe_2\left(SO_4\right)_3+6KOH->2Fe\left(OH\right)_3\downarrow+3K_2SO_4\)
\(Fe^{3+}+3OH^-->Fe\left(OH\right)_3\)
b) \(Pb\left(NO_3\right)_2+H_2S->PbS\downarrow+2HNO_3\)
\(Pb^{2+}+S^{2-}->PbS\)
c) \(Fe+6HNO_3-->Fe\left(NO_3\right)_3+3NO_2+3H_2O\)
\(Fe+6H^++3NO_3^-->Fe^{3+}+3NO_2+3H_2O\)