1.Temporary hardness:
Temporary hardness is caused by calcium or magnesium hydrogen carbonate.
So, to make Temporary water to soft water, we can boil this water or take the help of the following reactions:
Ca(HCO3)+Ca(OH)2→2CaCO3↓+2H2O
Mg(HCO3)2+2Ca(OH)2→2MgCO3+2H2O
MgCO3+Ca(OH)2→Mg(OH)2+CaCO3
2.Permanent hardness :
Permanent hardness is caused by calcium or magnesium sulphate.
So, to make Temporary water to soft water, I can take the help of the following reactions:
CaSO4+Na2CO3→CaCO3+Na2SO4
MgSO4+Na2CO3→MgCO3+Na2SO4
MgCO3+Ca(OH)2→Mg(OH)2+CaCO3