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NDA 1 2025 GAT, question 71

Topic: Chemistry

Q71

Which one of the following statements is NOT correct?

  1. (a) The molecules of soap are sodium or potassium salts of long chain fatty acids
  2. (b) The molecules of soap contain both hydrophobic and hydrophilic ends
  3. (c) Detergents are more effective than soaps in hard water
  4. (d) In micelles the ionic-end of the molecules is towards oil droplet while the other end faces outsideCorrect answer

Solution.

Answer: (d) In micelles the ionic-end of the molecules is towards oil droplet while the other end faces outside

  1. In a soap micelle in water, the non-polar hydrophobic tails point into the oil or grease, while the charged hydrophilic heads face the surrounding water.
  2. Option (d) reverses these directions.
  3. The other statements correctly describe soap and the usefulness of detergents in hard water.