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Hard water

What is hard water?


Hard water contains dissolved salts of calcium and magnesium. It gives poor lather with soap and hence is not intended to be used in laundries and in water boilers used in industries. It forms scales (also called lime scales) on the walls of the boilers and hence to be softened before its usage in industries.

The Ca2+ and Mg2+ ions in hard water precipitate soap. Soap is the sodium salt of fatty acid. It is soluble in water. But when it comes in contact with hard water, an insoluble precipitate of calcium or magnesium salt of fatty acid is formed. Hence lather is not formed.

When used in boilers, the calcium and magnesium salts are deposited on the walls of the boiler as scales during evaporation of water. These scales reduce the heat conductivity of boilers some times leading to the break down. 

Hard water is also responsible for the clogging of pipe lines. The soluble minerals are precipitated out due to evaporation of water or change in the pH of water or due to interaction with the metals used to make the pipe lines.

Types of Hardness:

1) Temporary hardness: The hardness of water which can be removed by boiling. It is caused by the presence of bicarbonates of calcium and magnesium in water. The bicarbonates are decomposed to insoluble carbonates upon boiling.

2) Permanent hardness: This type of hardness cannot be removed by boiling. It is caused by the presence of sulfates/chlorides of calcium and magnesium in water.

Related questions 

1) How do you remove permanent hardness of water?

2) What is degree of hardness of water?

Author: Aditya vardhan Vutturi