SiO+2NaOH=Na2SiO3+H2O
K2O+H2O=2KOH
MgO+2HCl=MgCl2+H2O
3SO2+Al2O3=Al2(SO3)3
2KOH+CuSO4=Cu(OH)2+K2SO4
Cu(OH)2+H2SO4=CuSO4+2H2O