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.

Sodium carbonate, Na2CO3, is also known as washing soda. It can remove temporary and permanent hardness from water. Sodium carbonate is soluble but calcium carbonate and magnesium carbonate are insoluble.

Sodium carbonate is used to remove both permanent and temporary hardness of the water.

Permanent hardness is due to the presence of sulfate, chloride, nitrate of magnesium and calcium.

Temporary hardness is due to the bicarbonate of calcium and magnesium.

Would salt in water is temporary or not?

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

So they can be removed by Na2co3.

Washing soda is called sodium carbonate.

What is the chemical reaction?

What is reference standard?

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

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 meant by permanent hardness of water?