Hard Water

& Soft Water

First Things First

What is Water Hardness?

Groundwater dissolves rocks and minerals releasing calcium, magnesium, and other ions that cause water to be hard. These

dissolved ions give hard water its characteristics.

Hard water

"Water that produces curd with soap and produces very little lather is called hard water.

Hard water affects cleaning ability of soap." Hard water contains bicarbonate, chlorides and

sulphates ( any one or all ) of calcium and magnesium .

Hard water

"Water that produces lather with soap easily is called soft water.

Soft water does not affect cleaning action of soap"

Soft water

Types of hard water?

Temporary hard water

Permanent hard water

Water that contains bicarbonate of calcium and magnesium or of both is called temporary hard water."

These bicarbonate are soluble in water and produce corresponding ions.

Mg(HCO3)2 è Mg+2 +2HCO3-1

Ca(HCO3)2 è Ca+2 + 2HCO3-1

TEMPORARY HARD WATER

Water that contains chlorides or sulphates of calcium or magnesium or of both is called Permanent water.

CaCl2è Ca+2 + 2Cl-1MgSO4 è Mg+2 + SO4-2

These compounds are soluble in water and produce corresponding ions.

PERMANENT HARD WATER

How to remove hardness of water?

There are two methods to remove hardness of water

CLARK'S METHOD.

ION-EXCHANGE METHOD.

In Clark’s method a calculated amount of calcium hydroxide Ca (OH)2 is added to hard water. Due to reaction, insoluble carbonates are obtained which are separated by filtration.

Ca(HCO3)2 + Ca(OH)2 è 2CaCO3 + 2H2O

Mg(HCO3)2 + Ca(OH)2 è CaCO3 + MgCO3 + 2H2O

CLARK'S METHOD

In this method sodium zeolite is used as ion-exchanger. Na-zeolite is passed through the pipes containing hard water. Sodium zeolite is converted into calcium-zeolite or magnesium-zeolite. These are insoluble in water and are separated from water by filtration.

Ca+2 + Na2-zeolite è Ca-zeolite + 2Na+1

Mg+2 +Na2-zeolite è Mg-zeolite + 2Na+1

ION-EXCHANGE METHOD

ION- EXCHANGE METHOD

Disadvantages of hard water

It costs youMONEY !!

Hardness minerals precipitate out of the water and form energy robbing scale.

General

Hard water affect cleaning ability of soap.

When hard water is used for washing, large amount of soap is consumed.

Domestic

Hard water can cause "Scaling" inside the pipes that transport water . Therefore if we use hard water in turbines and heat exchangers, their pipes will be corroded

Industrial

Hard water when used for drinking for long period can lead to stomach disorders. Especially hard water contains magnesium sulphate can weaken the stomach permanently.

Health

Advantages of Hard Water

Some people prefer the taste. Calcium ions in the water are good for children's

teeth and bones. It helps to reduce heart disease. Some brewers prefer using hard water for making

beer. A coating of limescale inside copper pipes, or

especially old lead pipes, stops poisonous salts dissolving into water.

Hard water contains calcium ions, Ca2+(aq), or magnesium ions, Mg2+(aq).

These ions react with soap, making it difficult to form a lather and producing scum.

Hard water can be softened by adding calcium hydroxide which makes insoluble carbonates which are separated by filtration .

Alternatively, the hard water can be passed through an ion-exchange resin in a column. Sodium ions replace the calcium ions in the water as it passes through the column.

summary

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