Q. 71. A solid is one which has fixed shape and volume. Talcum powder behaves as which type of substance?
(A) Solid
(B) Liquid
(C) combination of solid and liquid states
(D) combination of solid and gaseous states
Answer:
(A) Solid
Explanation:
Talcum powder flows easily because it consists of extremely fine particles, but each individual particle maintains a fixed shape and volume, classifying it as a solid.
Q. 72. What is the molecular mass of water (H2O)?
(A) 9 u
(B) 18 u
(C) 24 u
(D) 32 u
Answer:
(B) 18 u
Explanation:
The molecular mass of H2O is calculated by adding the atomic mass of 2 Hydrogen atoms (2 x 1u) and 1 Oxygen atom (16u) = 18 u.
Q. 73. Which of the following is an example of a colloid?
(A) Brass
(B) Gold
(C) Milky glass
(D) Water
Answer:
(C) Milky glass
Explanation:
Milky glass is a solid sol, a type of colloid where solid particles are dispersed within a solid medium.
Q. 74. An object weighs 10 N on Earth. What is its weight on the Moon?
(A) 1.67 N
(B) 16.7 N
(C) 60.7 N
(D) 167 N
Answer:
(A) 1.67 N
Explanation:
The acceleration due to gravity on the Moon is about 1/6th of that on Earth. Therefore, 10 N / 6 ≈ 1.67 N.
Q. 75. Which compound is most responsible for ozone layer depletion?
(A) Acid rain
(B) Carbonic acid
(C) Chlorofluorocarbons
(D) Fluorites
Answer:
(C) Chlorofluorocarbons
Explanation:
Chlorofluorocarbons (CFCs) release highly reactive chlorine atoms in the stratosphere when exposed to UV rays, breaking down ozone molecules.
