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Question
Explain the cleansing action of soap. Draw diagrams to illustrate your answer.
Solution
Cleansing action of soap: Soap forms a colloidal suspension when dissolved in water. The soap molecules group together to form spherical micelles. When a soiled cloth is immersed in soap water, the hydrocarbon ends of the soap molecules in the micelles entrap the oil and grease on cloth's surface. The ionic ends of the soap molecules in the micelles (having negative charges) are attached to the water. As the soiled cloth gets agitated in the soap solution, the oil and grease entrapped by the soap micelles get dispersed into the water and the soap water becomes dirty while the cloth gets rid of the dirt and becomes clean. Cleansing of the cloth is then done by thoroughly rinsing it in clean water.
The following diagram illustrates the cleansing action of soap:
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RELATED QUESTIONS
While preparing soap a small quantity of common salt is generally added to the reaction mixture of vegetable oil and sodium hydroxide. Which one of the following may be the purpose of adding common salt?
(A) To reduce the basic nature of the soap
(B) To make the soap neutral
(C) To enhance the cleansing power of the soap
(D) To favour the precipitation of the soap
In a locality, hard water, required for an experiment, is not available. However, the following salts are available in the school laboratory:
1. Sodium sulphate
2. Calcium sulphate
3. Magnesium chloride
4. Sodium chloride
5. Calcium chloride
6. Potassium sulphate
Which of the above salts may be dissolved in water to obtain hard water for the experiment?
(A) 2, 3 and 5
(B) 1, 2 and 5
(C) 1, 2, 4 and 6
(D) 3 and 5 only
State one use of saponification process.
Why is soap not suitable for washing clothes when the water is hard?
Which of the two is better for washing clothes when the water is hard: soap or detergent? Give reason for your answer.
How is soap made? Write a word equation involved in soap making.
A student is testing water to know which is best for cleansing purposes with soaps. He would find that the cleansing action of soaps is best when he uses water obtained from
(a) rain
(b) tap
(c) hand pump
(d) pond
Why are soaps not suitable for washing clothes when the water is hard?
Differentiate between:
Detergents and Soaps.
What are the differences between Bath soap and soap for washing clothes?
