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Carbon and its Compounds — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceCarbon and its Compounds5 Marks
Question
  1. You have three unlabelled test tubes containing ethanol, ethanoic acid and soap solution. Explain the method you would use to identify the compounds in different test tubes by chemical tests using litmus paper and sodium metal.
  2. Give the reason of formation of scum when soaps are used with hard water.
✓

Answer

  1.  
S.No.
Solution
Blue Litmus
Paper
Red Litmus
Paper
Sodium Metal
1.
Ethanol
No change
No change
Hydrogen gas
2.
Ethanoic acid
Turns red
No change
Hydrogen gas
3.
Soap
No change
Turns blue
Hydrogen gas
  1. The precipitate form of scum is formed when soap is used for washing clothes. With hard water, a large amount of soap is wasted in reacting with the calcium and magnesium ions of hard water to form an insoluble precipitate. The precipitate form formed by the action of hard water on soap, sticks to the clothes being washed and interferes with the cleaning ability of the additional soap. This makes the cleaning of clothes difficult.

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