Ans: (b)
50. What is "oxygen mixture"?
    (a) A mixture of potassium nitrate and carbon
    (b) A mixture of ammonium chloride and sodium nitrate
    (c) A mixture of potassium chlorate and manganese dioxide
    (d) A mixture of ammonium nitrate and charcoal
Ans: (c)
51. A mixture of carbon monoxide and hydrogen is
    (a) coal gas
    (b) producer gas
    (c) water gas
    (d) gobar gas
Ans: (c)
52. Harmful bacteria in drinking water cannot be destroyed by
    (a) chlorination
    (b) boiling
    (c) adding caustic soda
    (d) ozonisation
Ans: (c)
53. Temporary hardness is due to the presence of
    (a) calcium carbonate
    (b) calcium bicarbonate
    (c) magnesium sulphate
    (d) calcium sulphate
Ans: (b)
54. The gas used in balloons in the place of hydrogen is
    (a) nitrogen
    (b) helium
    (c) neon
    (d) argon
Ans: (b)
55. Tincture iodine is a solution of
    (a) iodine in potassium iodide
    (b) iodine in alcohol
    (c) iodine in water
    (d) iodine in carbon disulphide
Ans: (b)
56. Which of the following process involves removal of the elements of water?
    (a) Hydrolysis
    (b) Hydrogenation
    (c) Dehydration
    (d) Dehydrogenation
Ans: (c)
57. Which of the following types of water gives lather easily with soap?
    (a) Hard water
    (b) Heavy water
    (c) Soft water
    (d) Both (a) and (b)
Ans: (c)
58. Ozone occurs in the upper layers of air in the atmosphere because
    (a) it is lighter than air
    (b) in the lower layers it becomes unstable
    (c) ultra-violet light is present only in the upper layers
    (d) it mixes freely with O2 in the upper layers
Ans: (c)
59. The freezing point of water at 760 mm pressure is
    (a) 273 K
    (b) 0 K
    (c) 273°C
    (d) -273°C
Ans: (a)