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Carbon and its Compounds — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceCarbon and its Compounds1 Mark
MCQ
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.
  • ✓
    To favour the precipitation of the soap.
✓

Answer

Correct option: D.
To favour the precipitation of the soap.
Soap is sodium or potassium salt of fatty acids, and these salts are less soluble than a strong electrolyte sodium chloride.
So, sodium chloride is added to precipitate the soap by common-ion effect.

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