1. MgCl2+2NaOH=Mg(OH)2+2NaCl
Mg+2Cl+2Na+2OH=Mg(OH)2+2Na+2Cl
Mg+2OH=Mg(OH)2
2.Na2S+H2SO4=Na2SO4+H2S
2Na+S+2H+SO4=2Na+SO4+H2S
S+2H=H2S
3. ZnSO4+2NaOH=Zn(OH)2+Na2SO4
Zn+SO4+2Na+2OH=Zn(OH)2+2Na+SO4
Zn+2OH=Zn(OH)2
4. K2CO3+2HCl=2KCl+H2O+CO2
2K+CO3+2H+2Cl=2K+2Cl+H2O+CO2
CO3+2H=H2O+CO2