4. If one mixes up ashes with animal fat, the substance received in the crude form is called?
[UPSC NDA, General Ability Test — 18 Sept 2016]
(A) Pheromone
(B) Soap
(C) Cement
(D) Concrete
Answer: (B) Soap
Explanation: Wood ash traditionally supplied alkaline substances, which react with animal fats to form crude soap through saponification. The resulting fatty-acid salts can emulsify greasy matter. This early method preceded modern production with precisely measured sodium or potassium hydroxide solutions.
3. Cleansing action of soap occurs because
[Punjab Civil Service, Paper I — 2015]
(A) Oil and grease can be absorbed into the hydrophobic centres of soap micelles and get washed away
(B) Oil and grease can be absorbed into the hydrophilic centres of soap micelles and washed away
(C) Oil and grease can be absorbed into both hydrophilic and hydrophobic centres but not washed away
(D) Cleansing action is not related to micelles
Answer: (A) Oil and grease can be absorbed into the hydrophobic centres of soap micelles and get washed away
Explanation: Oily material is non-polar and associates with the hydrophobic interior of soap micelles. Hydrophilic carboxylate groups on the outer surface interact with water and stabilize the dispersion. This arrangement allows greasy dirt to be lifted and rinsed away.
2. The cleaning action of soap and detergent in water is due to the formation of
[UPSC NDA, General Ability Test — 19 Apr 2015]
(A) Micelle
(B) Salt
(C) Base
(D) Acid
Answer: (A) Micelle
Explanation: Surfactant molecules form micelles that surround non-polar dirt while exposing water-loving groups outward. This creates dispersed grease droplets that can be removed with water. Formation of an acid, base, or ordinary salt alone does not explain the cleaning mechanism.
1. Soaps are
[WBPSC Miscellaneous Preliminary Examination (2012 cycle), Shift 2 — 19 May 2013]
(A) Sodium and potassium salts of higher fatty acids
(B) Sodium salts of sulphonic acids
(C) High molecular mass alcohols
(D) Mixtures of glycerol and phenol
Answer: (A) Sodium and potassium salts of higher fatty acids
Explanation: Soaps are sodium or potassium salts of long-chain fatty acids, usually obtained when vegetable oils or animal fats undergo alkaline hydrolysis. Sodium salts of sulphonic acids more commonly describe certain synthetic detergents, while glycerol is a by-product of soap manufacture.
