121. Parsec is a measure of-
(a) Brightness of heavenly body
(b) Astronomical distance
(c) Density of stars
(d) Orbital velocity of giant stars

Answer. (d)- Orbital velocity of giant stars

122. By fixation of nitrogen is meant-
(a) Manufacture of nitrogen
(b) Liquefication of nitrogen
(c) Conversion of nitrogen into nitric acid
(d) Conversion of atmospheric nitrogen into
Useful compounds
(e) Mixing of nitrogen with other elements

Answer. (d)- Conversion of atmospheric nitrogen into
Useful compounds

123. Atoms of the same element, i. e., having the
Same atomic number that differ in atomic
Weight, are called-
(a) Isotopes
(b) Isomers
(c) Isobars
(d) Isohytes
(e) Isotherms

Answer. (a)Isotopes

124. The quantum number that tends to specify
The orientation in space for an orbital is the-
(a) Principal quantum number
(b) Orbital quantum number
(c) Magnetic quantum number
(d) Spin quantum number
(e) Azimuthal quantum number

Answer. (c)Magnetic quantum number

125. Carbohydrates are the compounds of-
(a) Carbon and hydrogen
(b) Carbon, oxygen and hydrogen
(c) Carbon, oxygen, hydrogen and nitrogen
(d) Carbon, nitrogen and hydrogen
(e) None of these

Answer. (b) Carbon, oxygen and hydrogen

126. The tides in the ocean are due to-
(a) Wind over the oceans
(b) Gravitational pull of the moon
(c) Rotation of the earth
(d) Revolution of the earth

Answer. (b) Gravitational pull of the moon

127. When water freezes its density-
(a) Increases
(b) Decreases
(C) remains constant
(d) Becomes zero

Answer. (b) Decreases

128. A chemical reaction that takes place with
the evolution of heat is called a/an-
(a) Reversible reaction
(b) Endothermic reaction
(c) Thermal reaction
(d) Exothermic reaction
(e) Irreversible reaction

Answer. (d) Exothermic reaction

129. The manufacture of iron ore
Involves the process of-
(a) Oxidation
(b) Reduction
(c) Fractional distillation
(d) Electrolysis
(e) None of the above

Answer. (b) Reduction

130. A double convex air bubble in water would
Behave as a-
(a) Convergent lens
(b) Divergent lens
(c) Both as convergent and divergent lenses
(d) None of them

Answer. (b) Divergent lens

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