Ans: (c)
137. The hygrometer is an apparatus used for finding the
   (a) temperature of air
   (b) intensity of light
   (c) density of a liquid
   (d) relative humidity of the atmosphere
Ans: (d)
138. In a refrigerator, the refrigerant is
   (a) Nitrogen
   (b) Oxygen
   (c) Chlorine
   (d) Freon
Ans: (d)
139. Which of the following is known as freon?
   (a) Liquid ammonia
   (b) Carbon tetrafluoride
   (c) Dichloro-difluoro-methane
   (d) Sulphur dioxide
Ans: (c)
140. Increase in pressure
   (a) has no effect on the boiling point of a liquid
   (b) raises the boiling point of a liquid
   (c) lowers the boiling point of a liquid
   (d) increases the volume of a liquid
Ans: (b)
141. The pressure of air at high altitude is less than the atmospheric pressure at
   the sea level. Hence the boning point of water at a hill top
   (a) is more than at sea level
   (b) is equal to that sea level
   (c) is less than at sea level
   (d) depends on the surrounding temperature
Ans: (c)