a) \(Cr{\left( {N{O_3}} \right)_3} + 3NaOH \to Cr{\left( {OH} \right)_3} \downarrow + 2NaN{O_3}\)
\(\left( {C{r^{3 + }} + 3O{H^ - } \to Cr{{\left( {OH} \right)}_3} \downarrow } \right)\)
b) \(AlC{l_3} + 3NaOH \to Al{\left( {OH} \right)_3} \downarrow + 3NaCl\)
\(\left( {A{l^{3 + }} + 3O{H^ - } \to Al{{\left( {OH} \right)}_3} \downarrow } \right)\)
c) \(NiS{O_4} + 2NaOH \to Ni{\left( {OH} \right)_2} \downarrow + N{a_2}S{O_4}\)
\(\left( {N{i^{2 + }} + 2O{H^ - } \to Ni{{\left( {OH} \right)}_2} \downarrow } \right)\)