Try each question on your own first. Use the Show Answer button only after you have selected your option, then read the explanation and revise the related concept from your chapter notes.
21. 5% to 8% solution of acetic acid in water is known as:
A. Absolute alcohol
B. Rectified spirit
C. Vinegar
D. Formalin
Answer: C. Vinegar
Explanation: A 5-8% solution of ethanoic acid (acetic acid) in water is widely used as a preservative known as vinegar.
22. Why is pure ethanoic acid often called 'glacial acetic acid'?
A. It glows in the dark
B. It freezes into ice-like crystals at 290 K (17°C)
C. It is extracted from glaciers
D. It turns white on boiling
Answer: B. It freezes into ice-like crystals at 290 K (17°C)
Explanation: Because its melting point is 290 K, pure ethanoic acid often freezes during winters in cold climates.
23. In a soap molecule, the ionic end is:
A. Hydrophobic (water repelling)
B. Hydrophilic (water loving)
C. Lipophilic (oil loving)
D. Non-polar
Answer: B. Hydrophilic (water loving)
Explanation: The ionic head of a soap molecule interacts with water (hydrophilic), while the long hydrocarbon tail interacts with oil (hydrophobic).
24. Spherical clusters formed by soap molecules in water during cleaning action are called:
A. Emulsions
B. Micelles
C. Precipitates
D. Colloids
Answer: B. Micelles
Explanation: Soap molecules align with hydrophobic tails inwards toward oil droplets, forming structures called micelles.
25. What insoluble precipitate (scum) is formed when soap is used in hard water?
A. Calcium and Magnesium salts of fatty acids
B. Sodium and Potassium salts
C. Iron oxide
D. Sodium chloride
Answer: A. Calcium and Magnesium salts of fatty acids
Explanation: Soap reacts with Ca²⁺ and Mg²⁺ ions present in hard water to form an insoluble sticky precipitate called scum.
26. Detergents are ammonium or sulfonate salts of long chain carboxylic acids that:
A. Do not form scum with hard water
B. Form scum only in warm water
C. Cannot clean oil stains
D. Are non-synthetic
Answer: A. Do not form scum with hard water
Explanation: Detergents remain soluble and effective even in hard water because their charged ends do not form insoluble precipitates with Ca²⁺ or Mg²⁺.
27. What is the molecular formula of Cyclohexane?
A. C₆H₆
B. C₆H₁₂
C. C₆H₁₄
D. C₅H₁₀
Answer: B. C₆H₁₂
Explanation: Cyclohexane is a cyclic saturated hydrocarbon with formula C₆H₁₂.
28. What is the chemical formula of Benzene?
A. C₆H₁₂
B. C₆H₆
C. C₆H₁₄
D. C₂H₂
Answer: B. C₆H₆
Explanation: Benzene is a cyclic unsaturated aromatic hydrocarbon with formula C₆H₆ (alternating single and double bonds).
29. The IUPAC name of Propanone belongs to which family of organic compounds?
A. Alcohol
B. Aldehyde
C. Ketone
D. Carboxylic acid
Answer: C. Ketone
Explanation: Propanone (CH₃COCH₃) ends with suffix '-one', indicating it is a ketone.
30. Unsaturation in hydrocarbons can be tested by the discoloration of:
A. Lime water
B. Bromine water
C. Litmus solution
D. Phenolphthalein
Answer: B. Bromine water
Explanation: Unsaturated hydrocarbons (alkenes/alkynes) decolorize reddish-brown bromine water through addition reactions.
This page contains a chapter-wise objective practice set. Try the questions without checking the answer first, then use the explanation to understand the point you missed. The current page contains 30 questions, so you can practise in smaller sets when you are revising.
Quick revision tip
After the practice set, write down the question numbers you missed and revise only those concepts once more. This makes MCQ practice more useful than repeatedly attempting the same questions without reviewing mistakes.
