General Knowledge - General Science - Discussion

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).

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 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.

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.

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.

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

So they can be removed by Na2co3.

What is reference standard?

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

Thats is why sodium carbonate is also used for detergents.

What is meant by permanent hardness of water?

Washing soda is called sodium carbonate.