Hardness of water

[Sandeep Bhardwaj]

Hardness of water is caused by bicarbonate and carbonate of calcium and maganesium. calcium carbonate is insoluble salt so why do we consider it as hardness causing agent.

[Ratnakar Pandey]

Since it is insoluble in water therefore causes hardness in water otherwise it would be known as soft water....... so simple.

[Sandeep Bhardwaj]

sorry sir when something is insoluble how can we say the hardness is due to this because hard water is the one in which soap don't form lather with water but the insoluble part can't restrict it with leather formation so it play no roll in hardness. i am still in confusion.

[Ratnakar Pandey]

You need to understand basics of hardness:

• The hardness caused due to the presence of bicarbonates of calcium and magnesium is known as temporary hardness
• Dissolving these minerals yield calcium and magnesium cations (Ca²⁺, Mg²⁺) and carbonate and bicarbonate anions (CO₃^2-, HCO₃^-).The presence of the metal cations makes the water hard. Temporary hardness can be reduced either by boiling the water, or by the addition of lime (CaOH) through the softening process. Boiling of water promotes the formation of carbonate from the bicarbonate and precipitates calcium carbonate out of solution, leaving water that is softer upon cooling.
• With hard water, soap solutions form a white precipitate instead of producing lather. This effect arises because the 2+ ions destroy the surfactant properties of the soap by forming a solid precipitate. A major component of such precipitate is calcium stearate, which arises from sodium stearate, the main component of soap:

             2 C₁₇H₃₅COO^- + Ca²⁺ → (C₁₇H₃₅COO)₂Ca

• The hardness caused due to the presence of chlorides and sulphates of calcium and magnesium known as Permanent hardness.
• Ions causing permanent hardness of water can be removed using a water softener, or ion exchange column. It cannot be removed by boiling

 Hope this will clarify you.