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CHEMISTRY CBSE CLASS X

Soaps and Detergents

Micelle

A spherical aggregate of soap molecules in the soap solution in water.

• Soap solution is a colloidal solution. A soap solution appears cloudy because the soap micelles are large enough to scatter light.

Limitations of soaps

 Soap is not suitable for washing clothes with hard water -

1. Large amt. of soap is wasted in reacting with calcium and magnesium ions of hard water to from insoluble precipitate called scum . So larger amount of soap is needed.
2. The scum formed sticks to the clothes and interferes with the cleaning ability of the additional soap , making cleaning difficult.

• Hard water contains calcium and magnesium salts.

Detergents

It is the sodium salt of a long chain benzene sulphonic acid ( or the sodium salt of a long chain alkyl hydrogensulphate) which has cleansing properties in water.

They are also called soap-less soaps because though they act like a soap in having the cleansing properties, they do not contain the usual soaps like sodium stearate , etc.

• Detergents are better cleansing agents than soaps because they do not form insoluble calcium and magnesium salts with hard water and can be used for washing even with hard water.

Advantages of detergents

1. Can be used with hard water
2. Have strong cleansing action than soap.
3. More soluble in water than soaps.

Disadvantage of detergents over soaps

Some detergents are biodegradable , they cannot be decomposed by micro organisms like bacteria and hence cause water pollution in lakes and rivers .All  soaps are bio- degradable and do not cause pollution.

Submitted By Mrs. Kritika Bhola
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