Carbon and Its Compounds Part 3: MCQs (Q51–Q75)

🧪 Carbon and Its Compounds – Class 10 Science MCQs

Part 3: Soaps, Detergents, Micelles & Applications (Q51–Q75)

Q51. Soaps are salts of:

A. Fatty acids with Na or K
B. Hydrochloric acid
C. Sulphuric acid
D. Nitric acid

✅ Correct Answer: A. Fatty acids with Na or K

Soaps = sodium or potassium salts of long-chain carboxylic acids.

Q52. Detergents are:

A. Sodium salts of carboxylic acids
B. Ammonium or sulphonate salts of hydrocarbons
C. Potassium carbonate
D. Sodium bicarbonate

✅ Correct Answer: B. Ammonium or sulphonate salts of hydrocarbons

Synthetic detergents = sulphates/sulphonates of hydrocarbons.

Q53. Which statement is true about soaps?

A. Work well in hard water
B. Form scum with Ca²⁺, Mg²⁺ salts
C. Are non-biodegradable
D. Are synthetic in nature

✅ Correct Answer: B. Form scum with Ca²⁺, Mg²⁺ salts

Q54. Detergents are better than soaps in hard water because:

A. They are cheaper
B. They do not form scum with Ca²⁺, Mg²⁺
C. They are natural products
D. They are weak salts

✅ Correct Answer: B. They do not form scum with Ca²⁺, Mg²⁺

Q55. The cleaning action of soaps is due to formation of:

A. Hydrogen bonds
B. Ionic bonds
C. Micelles
D. Colloids

✅ Correct Answer: C. Micelles

Soap molecules arrange into micelles, trapping dirt in their hydrocarbon tails.

Q56. Which part of the soap molecule is hydrophobic?

A. Ionic head (–COO⁻)
B. Hydrocarbon tail
C. Water molecules
D. Salt ions

✅ Correct Answer: B. Hydrocarbon tail

Hydrophobic tail avoids water, attaches to grease/dirt.

Q57. Which part of the soap molecule is hydrophilic?

A. Hydrocarbon chain
B. Ionic head group
C. Both head & tail
D. None

✅ Correct Answer: B. Ionic head group

Hydrophilic head interacts with water.

Q58. Micelle formation occurs when soap concentration is:

A. Above critical micelle concentration (CMC)
B. Below CMC
C. Zero
D. Equal to 1%

✅ Correct Answer: A. Above CMC

Q59. The tail of soap molecule is:

A. Polar
B. Non-polar
C. Ionic
D. Hydrophilic

✅ Correct Answer: B. Non-polar

Tail = hydrocarbon chain, soluble in oil/grease.

Q60. The head of soap molecule is:

A. Non-polar
B. Hydrophobic
C. Hydrophilic and ionic
D. Greasy

✅ Correct Answer: C. Hydrophilic and ionic

Q61. Which of the following is a disadvantage of detergents?

A. They are expensive
B. They are non-biodegradable
C. They form scum in hard water
D. They do not clean well

✅ Correct Answer: B. They are non-biodegradable

Some detergents persist in environment.

Q62. Which of the following is biodegradable?

A. Soap
B. Detergent
C. Plastic
D. Polythene

✅ Correct Answer: A. Soap

Q63. Which compound is used in making soaps?

A. Na₂CO₃
B. NaCl
C. NaOH or KOH
D. HCl

✅ Correct Answer: C. NaOH or KOH

Fats + NaOH/KOH → Soap + Glycerol (saponification).

Q64. Saponification is the reaction of:

A. Ester + NaOH → Soap + Alcohol
B. Acid + Base → Salt + Water
C. Alcohol + Acid → Ester + Water
D. Hydrocarbon + O₂ → CO₂ + H₂O

✅ Correct Answer: A. Ester + NaOH → Soap + Alcohol

Q65. Which compound is a by-product of saponification?

A. CO₂
B. Glycerol
C. Methane
D. Vinegar

✅ Correct Answer: B. Glycerol

Q66. Which statement about detergents is correct?

A. They cannot clean in acidic water
B. They work well even in hard water
C. They are salts of fatty acids
D. They always contain KOH

✅ Correct Answer: B. They work well even in hard water

Q67. Soaps form scum in hard water because of:

A. Reaction with Mg²⁺, Ca²⁺ ions
B. Reaction with Na⁺ ions
C. Presence of Cl⁻ ions
D. Low temperature

✅ Correct Answer: A. Reaction with Mg²⁺, Ca²⁺ ions

Q68. Which is the correct reaction for soap formation?

A. Fat + NaOH → Soap + Glycerol
B. Fat + HCl → Soap + Glycerol
C. Fat + KCl → Soap + H₂O
D. Fat + NaCl → Soap + Alcohol

✅ Correct Answer: A. Fat + NaOH → Soap + Glycerol

Q69. Which is an application of micelle formation?

A. Rusting prevention
B. Cleaning clothes with soap
C. Making alloys
D. Electrolysis

✅ Correct Answer: B. Cleaning clothes with soap

Q70. Detergents are preferred over soaps in:

A. Hard water
B. Distilled water
C. Soft water
D. Rain water

✅ Correct Answer: A. Hard water

Q71. Which of the following soaps is soft soap?

A. Sodium soap
B. Potassium soap
C. Calcium soap
D. Magnesium soap

✅ Correct Answer: B. Potassium soap

Potassium soaps are softer and used in shaving creams.

Q72. Soap solution in water forms:

A. Suspension
B. True solution
C. Colloidal solution
D. Gel

✅ Correct Answer: C. Colloidal solution

Q73. The cleansing property of soap depends on:

A. Micelle formation
B. Sublimation
C. Oxidation
D. Fermentation

✅ Correct Answer: A. Micelle formation

Q74. Detergents are generally made from:

A. Petrochemicals
B. Animal fats
C. Plant oils
D. Glycerol

✅ Correct Answer: A. Petrochemicals

Q75. Which of the following is NOT an application of carbon compounds?

A. Alcohols used in fuels
B. Carboxylic acids in vinegar
C. Esters in perfumes
D. Graphite used as fertilizer

✅ Correct Answer: D. Graphite used as fertilizer

Graphite is used as lubricant and electrodes, not fertilizer.

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