Na + H[tex]_{2}[/tex]O ----- NaOH +H[tex]_{2}[/tex]
Na2O +H2O -----NaOH
Fe + HCl = FeCl2 + H2
Fe + Cl2 = FeCl3
Mg + AlCl3 = Al + MgCl2
Zn + Pb(No3)2 = Pb + Zn(No3)
