60. Reduction involves
    (a) loss of electrons
    (b) gain of electrons
    (c) gain of oxygen
    (d) removal of hydrogen
Ans: (b)
61. The presence of dust particles in air serves
    (a) as a nucleus to condense water vapour resulting in rain
    (b) to maintain the average density of air
    (c) to minimise the inflammatory nature of oxygen
    (d) to protect the inhabitants of the earth from the effects of ultra violet rays.
Ans: (a)
62. Water always contains hydrogen and oxygen in the ratio 1:8 by weight. This is in accordance with the
    (a) Law of Multiple Proportions
    (b) Law of Definite Proportions
    (c) Law of Conservation of Mass
    (d) Law of Reciprocal Proportions
Ans: (b)
63. The substance most abundantly found in sea water is
    (a) magnesium chloride
    (b) sodium chloride
    (c) calcium sulphate
    (d) potassium chloride
Ans: (b)
64. The compounds produced by plants in the process of photosynthesis are
    (a) carbohydrates
    (b) proteins
    (c) salts
    (d) fats
Ans: (a)
65. In the common soda-acid fire extinguisher, the fire is put out by
    (a) acid fumes
    (b) sodium bicarbonate
    (c) carbon dioxide
    (d) sodium carbonate
Ans: (c)
66. The substance preserved under water is
    (a) potassium
    (b) sodium
    (c) red phosphorus
    (d) white phosphorus
Ans: (d)
67. The metal which reacts most violently with cold water is
    (a) calcium
    (b) sodium
    (c) magnesium
    (d) potassium
Ans: (d)
68. Clark"s method for removal of temporary hardness in water uses
    (a) calcium hydroxide
    (b) washing soda
    (c) calcium chloride
    (d) zeolite
Ans: (a)
69. Suspended impurities in water are effectively removed by
    (a) adding milk of lime
    (b) filtering through sand
    (c) adding filter alum
    (d) chlorination
Ans: (c)
70. Heavy water was discovered by
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