General Knowledge - General Science - Discussion

Permanent hardness of water is due to dissolved salts of chlorides and sulphates of calcium and magnesium which can be removed by adding sodium carbonate (Na2CO3) (washing soda or soda ash) which reacts with these dissolved salts to form insoluble carbonates that can be removed by filtration and then water becomes soft.

Permanent hardness is due to magnesium or calcium chloride. Therefore by the addition of sodium carbonate it is removed in the form of sodium chloride.

Thats is why sodium carbonate is also used for detergents.

What is meant by permanent hardness of water?

The hardness of water can be either temporary or permanent.

Temporary hardness can be removed simply by boiling the water.

Permanent hardness cannot be removed by boiling but can often be removed by chemical treatment.

Temporary hardness is caused by calcium and/or magnesium hydrogencarbonate. These are formed as carbonated rain water passes over rocks containing carbonate ions, for example,

H2O(l) + CO2(g) + CaCO3(s) Ca(HCO3)2(aq).

H2O(l) + CO2(g) + MgCO3(s) Mg(HCO3)2(aq).

Permanent hardness is caused by calcium and/or magnesium sulphate. These are formed as water passes over rocks containing sulphate ions, for example,

aq. + CaSO4(s)Ca2+(aq) + SO42-(aq).

aq. + MgSO4(s)Mg2+(aq) + SO42-(aq).

What is reference standard?

Why we use caco3 for finding the strength of degree of hardness?

What is the chemical reaction?

Washing soda is called sodium carbonate.

Yes, in hard water magnesium bicarbonate, chloride-bicarbonate.

So they can be removed by Na2co3.

Would salt in water is temporary or not?