14. Which of the following statements is TRUE with respect to soaps?
[Delhi Police Head Constable (AWO/TPO), Shift 2 — 28 Oct 2022]
(A) Soaps that float in water are made by dissolving the soap in ethanol and then evaporating the excess solvent
(B) Transparent soaps are made by beating tiny air bubbles before their hardening
(C) Shaving soaps contain glycerol to prevent rapid drying
(D) Toilet soaps contain fillers like sodium rosinate, sodium silicate, borax and sodium carbonate
Answer: (C) Shaving soaps contain glycerol to prevent rapid drying
Explanation: Glycerol is added to shaving soap as a moisture-retaining agent, helping the soap and lather remain usable instead of drying rapidly. Floating soaps are made by entraining air; ethanol helps transparency. Industrial fillers are more characteristic of laundry soaps.
13. Which of the following statements are CORRECT about soap?
(I) Transparent soaps are made by dissolving soap in ethanol and evaporating excess solvent.
(II) Shaving soaps contain sodium rosinate to prevent rapid drying.
(III) Dye does not absorb evenly on cloth washed with soap using hard water because of an insoluble gummy precipitate.
[Delhi Police Head Constable (AWO/TPO), Shift 1 — 27 Oct 2022]
(A) I and II
(B) I and III
(C) II and III
(D) I, II and III
Answer: (B) I and III
Explanation: Ethanol can be used in producing transparent soap, and hard-water ions create gummy soap scum that interferes with fabric treatment. Statement II misidentifies sodium rosinate as the anti-drying additive; glycerol is primarily added to retain moisture in shaving soap.
12. Which of the following is left in the sodium hydroxide solution after removing the soap?
[Delhi Police Head Constable (AWO/TPO), Shift 3 — 27 Oct 2022]
(A) Alcohol
(B) Glycerol
(C) Esters
(D) Phenol
Answer: (B) Glycerol
Explanation: During saponification, a triglyceride reacts with sodium hydroxide to yield soap and glycerol. When the relatively insoluble soap is separated, glycerol remains dissolved in the aqueous layer. It is a valuable three-hydroxyl alcohol used in cosmetics and pharmaceuticals.
11. Which inorganic compound is used to manufacture soap, rayon, paper, explosives, dyes, and petroleum products?
[SSC CHSL (2021 cycle), Shift 1 — 25 May 2022]
(A) NaOCl
(B) NaOH
(C) CaOCl₂
(D) NaHCO₃
Answer: (B) NaOH
Explanation: Sodium hydroxide is caustic soda, a strong alkali used to saponify fats in soap manufacturing. It also serves in paper pulping, textile processing, and various chemical industries. Sodium hypochlorite and bleaching powder instead are mainly valued as oxidizing or bleaching agents.
10. The hardness of water is estimated by
[WBCS Mains 2021, Paper IV (held May 2022) — May 2022]
(A) Conductivity method
(B) EDTA method
(C) Titrimetric method
(D) Distillation method
Answer: (B) EDTA method
Explanation: EDTA complexometric titration measures calcium and magnesium ions responsible for water hardness. These ions otherwise react with soap to produce scum. The method uses a suitable indicator, often Eriochrome Black T, to identify the titration endpoint and calculate total hardness.
9. Detergents are –
[UPPSC GIC Lecturer, Chemistry — 2021]
(A) Triglycerides of fatty acids
(B) Sodium salts of higher fatty acids
(C) Sodium salts of alkyl sulphonates
(D) Hydrogenated products of long-chain fatty acids
Answer: (C) Sodium salts of alkyl sulphonates
Explanation: Common synthetic anionic detergents include sodium alkyl sulphonates and related sulphates. They have long hydrocarbon chains and polar cleaning groups. In contrast, sodium salts of higher fatty acids are conventional soaps, which can form scum with hard-water minerals.
8. Which of the following can be used as soap?
[Bihar STET PGT Chemistry, Paper II, Shift 1 — 18 Sept 2020]
(A) C₁₇H₃₅COONa
(B) (C₁₇H₃₅COO)₂Ca
(C) C₁₇H₃₅COOH
(D) C₁₇H₃₁COOH
Answer: (A) C₁₇H₃₅COONa
Explanation: C₁₇H₃₅COONa is sodium stearate, a sodium salt of the long-chain fatty acid stearic acid. It functions as soap. Calcium stearate is poorly water-soluble, while the free carboxylic acids listed are not themselves sodium or potassium soaps.
7. What is the dominant chemical present in detergent powder?
[SSC CGL, Shift 1 — 12 Jun 2019]
(A) Calcium carbonate
(B) Sodium carbonate
(C) Hydrochloric acid
(D) Sodium alkyl sulphate
Answer: (B) Sodium carbonate
Explanation: Sodium carbonate, known as soda ash or washing soda in hydrated form, is a common major builder in many powdered laundry detergents. It provides alkalinity and helps soften water. The actual dominant ingredient varies by brand and formulation; the recorded exam key identifies sodium carbonate.
6. Which of the following is a non-biodegradable detergent?
[MP HSTET Varg 1 (2018 cycle), Chemistry, Shift 1 — 7 Feb 2019]
(A) Sodium-4-(1-dodecyl)benzenesulphonate
(B) Sodium-4-(1,3,5,7-tetramethyloctyl)benzenesulphonate
(C) Sodium-4-(2-dodecyl)benzenesulphonate
(D) Sodium lauryl sulphate
Answer: (B) Sodium-4-(1,3,5,7-tetramethyloctyl)benzenesulphonate
Explanation: The second compound contains a highly branched hydrocarbon chain, making it difficult for many microorganisms to degrade. Linear detergent chains are generally broken down more readily. Persistent branched surfactants can contribute to foaming and pollution in receiving water bodies.
5. Which of the following statements are CORRECT?
I. Soap molecules form structures called micelles.
II. Soap micelles cannot scatter light.
III. Oily dirt gets collected in the centre of the micelle.
[SSC CHSL, Shift 1 — 22 Mar 2018]
(A) Both I and II
(B) Both I and III
(C) Both II and III
(D) All I, II and III
Answer: (B) Both I and III
Explanation: Soap molecules aggregate into micelles in water, and grease becomes trapped within their non-polar cores. Statement II is incorrect because micelles are colloidal particles capable of scattering light. Therefore statements I and III, but not II, are correct.
