Question

What is the cause of the hardness of water?

Answer 1

Hard water

• Water that does not form lather with soap solution is called hard water.
• The hardness of water is due to the presence of dissolved $\mathrm{Calcium}\left(\mathrm{Ca}\right)$ and $\mathrm{Magnesium}\left(\mathrm{Mg}\right)$ salts.
• There are two types of hardness which are temporary hardness and permanent hardness.
• The hardness of water due to the presence of dissolved $\mathrm{Calcium}\left(\mathrm{Ca}\right)\mathrm{and}\mathrm{Magnesium}\left(\mathrm{Mg}\right)\mathrm{bicarbonates}$ is called temporary hardness. It is removed by boiling.
• The hardness of water due to the presence of dissolved $\mathrm{Calcium}\left(\mathrm{Ca}\right)\mathrm{and}\mathrm{Magnesium}\left(\mathrm{Mg}\right)\mathrm{chlorides}\mathrm{and}\mathrm{sulphates}$ is called permanent hardness. permanent hardness can be removed by adding $\mathrm{Washing}\mathrm{soda}\left({\mathrm{Na}}_2{\mathrm{CO}}_3\right)$.