Previous Year’s CBSE Boards Questions – Soaps and Detergents (Carbon and its Compounds)

Soaps and Detergents –

1. Give reasons for the following observation –
   Use of synthetic detergents causes pollution of water.
   (1/3 mark, Delhi 2009)
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2. Explain the cleansing action of soap.
   (2/5 marks, Foreign 2009)
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3. Why does micelle formation take place when soap is added to water? Why are micelles not formed when soap is added to ethanol?
   (3/5 marks,  AI 2011)
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4. (a) What is a soap? Why are soaps not suitable for washing clothes when the water is hard?
   (b) Explain the action of soap in removing an oily spot from a piece of cloth.
   (5 marks,  Delhi 2011)
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5. (a) What is a detergent? Name one detergent.
   (b) Write two advantages and two disadvantages of using detergents over soaps.
   (c) Why by using detergent, can we wash clothes even in hard water?
   (5 marks,  Foreign 2011)
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6. What is the difference between the chemical composition of soaps and detergents? State in brief the action of soaps in removing an oily spot from a shirt. Why are soaps not considered suitable for washing where water is hard?
   (5 marks, Delhi 2012)
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7. What are detergents chemically? List two merits and two demerits of using detergents for cleansing. State the reason for the suitability of detergents for washing, even in the case of the water having calcium and magnesium ions.
   (5 marks, AI 2012)
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8. What are soap and detergents chemically? Explain the action of cleaning by soaps. State the reason why we can wash our clothes even in hard water using detergents.
   (5 marks, Foreign 2012)
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9. What is the difference between the molecules of soaps and detergents, chemically? Explain the cleansing action of soaps.
   (5 marks, Delhi 2015)
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10. Soaps and detergents are both, types of salts. State the difference between the two. Write the mechanism of the cleansing action of soaps. Why do soaps not form lather (foam) with hard water? List two problems that arise due to the use of detergents instead of soaps.
    (5 marks, Delhi 2017, AI 2015)
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11. What are micelles? Why does it form when soap is added to water? Will a micelle be formed in other solvents such as ethanol also? State briefly how the formation of micelles help to clean the clothes having oily spots.
    (5 marks, Foreign 2016)
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12. (a) You have three unlabeled test tubes containing ethanol, ethanoic acid and soap solution. Explain the method you would use to identity the compounds in different test tubes by chemical tests using litmus paper and sodium metal.
    (b) Give the reason of formation of scum when soaps are used with hard water.
    (5 marks, Foreign 2016)
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