Cr3+ + 3OH- \rightarrow Cr(OH)\Rightarrow Cr2(SO)3 + 6NaOH \rightarrow 2Cr(OH)3 +3NaSO4Pb2+ + S- \rightarrow PbS\Rightarrow PbSO4 + Na2S \rightarrow NaSO4 +PbSAg+ + Cl- \rightarrow AgCl\Rightarrow AgNO3 + HCl \rightarrow AgCl + HNO3Ca2+ + PO43- \rightarrow Ca3(PO4)2 \Rightarrow 3Ca(OH)2 + 2Na3PO4 \rightarrow Ca3(PO4)2 + 6NaOH
Cr3+ + 3OH- -> Cr(OH)=> Cr2(SO)3 + 6NaOH -> 2Cr(OH)3 +3NaSO4Pb2+ + S- -> PbS=> PbSO4 + Na2S -> NaSO4 +PbSAg+ + Cl- -> AgCl=> AgNO3 + HCl -> AgCl + HNO3Ca2+ + PO43- -> Ca3(PO4)2 => 3Ca(OH)2 + 2Na3PO4 -> Ca3(PO4)2 + 6NaOH