Soaps and Detergents Cleansing Action - UNSOLVED PRACTICE SET
Chapter: Carbon and Its Compounds | Topic: Soaps and Detergents Cleansing Action
SOAPS AND DETERGENTS CLEANSING ACTION - UNSOLVED PRACTICE SET
Topic: Soaps and Detergents Cleansing Action
Multiple Choice Questions
Q1. Soaps are sodium or potassium salts of:
- Long-chain carboxylic acids
- Long-chain alcohols
- Sulphonic acids
- Mineral acids
Q2. The process of making soap from fats and oils is called:
- Fermentation
- Hydrogenation
- Saponification
- Combustion
Q3. Which part of a soap molecule is water-repelling?
- Hydrophilic head
- Hydrophobic tail
- Ionic end
- Polar group
Q4. Detergents are preferred over soaps for washing clothes in hard water because:
- Detergents are cheaper
- Detergents do not form insoluble scum with hard water
- Detergents are natural products
- Detergents are biodegradable
Q5. The ions responsible for the hardness of water are:
- Sodium and potassium ions
- Calcium and magnesium ions
- Chloride and sulphate ions
- Hydrogen and hydroxide ions
Q6. Micelles are formed when:
- Soap molecules arrange themselves with their hydrophobic tails inward and hydrophilic heads outward in water
- Soap molecules dissolve completely in water
- Soap molecules react with hard water
- Soap molecules evaporate
Short Answer Questions
Q7. What is saponification? Write the general chemical equation for the preparation of soap.
Q8. Explain why soap does not work well in acidic water.
Q9. Distinguish between soap and detergent on the basis of:
(a) Chemical composition
(b) Effect in hard water
Q10. Draw a labelled diagram of a soap micelle and explain how it helps in cleansing.
Q11. Your mother uses both soap and detergent powder for washing. She notices that soap does not lather well with groundwater (hard water), but detergent powder works fine. Explain why this happens.
Q12. Why are detergents considered to cause water pollution, while soaps are considered more environmentally friendly?
Long Answer Questions
Q13. Describe the cleansing action of soap with a neat labelled diagram. Explain the role of micelles in removing grease and oil from dirty clothes. Why does soap not work effectively in hard water?
Q14. Compare soaps and detergents on the following basis:
(a) Chemical structure
(b) Raw materials used
(c) Effectiveness in hard water
(d) Environmental impact
Give one example each of a soap and a detergent.
Q15. During a visit to a soap factory, you observe the process of soap making.
(a) Name the raw materials used in soap manufacture.
(b) What is the role of sodium hydroxide in this process?
(c) Why is common salt (NaCl) added to the reaction mixture after saponification?
(d) The factory also produces liquid soap. How is liquid soap different from solid soap in terms of the alkali used?
Numerical / Application-Based Problems
Q16. In a soap-making experiment, 100 g of a vegetable oil (mainly glyceryl stearate, C₅₇H₁₁₀O₆) reacts with sodium hydroxide.
(a) Write the general equation for saponification.
(b) If 1 mole of oil produces 3 moles of soap (sodium stearate, C₁₇H₃₅COONa), calculate the mass of soap produced from 100 g of oil. (Molar mass of oil = 890 g/mol, Molar mass of sodium stearate = 306 g/mol)
(c) Why is glycerol considered a valuable by-product of this reaction?
Q17. A family uses 2 kg of detergent powder per month for washing clothes. The detergent contains sodium lauryl sulphate (C₁₂H₂₅SO₄Na) as the active ingredient.
(a) Why does this detergent work well even in hard water?
(b) If the detergent powder contains 20% active ingredient by mass, calculate the mass of sodium lauryl sulphate used in one month.
(c) Why do environmentalists recommend using soap instead of detergent for washing near lakes and rivers?
Q18. A soap manufacturer wants to test the effectiveness of two soaps — Soap A (made from coconut oil) and Soap B (made from animal fat) — in hard water containing calcium ions.
(a) Write the chemical equation for the reaction of soap (sodium stearate, C₁₇H₃₅COONa) with calcium chloride (CaCl₂) in hard water.
(b) What is the common name of the insoluble substance formed? Why does it reduce the cleansing action?
(c) Suggest one way to make soap work better in hard water without switching to detergent.