D Mercury      4. Malachite
          A         B        C         D
     (a)  4         3        2         1
     (b)  2         3        4         1
     (c)  3         1        2         4
     (d)  1         2        3         4
Ans: (b)
168. When the temperature of a gas sample filled in a container is increased, its pressure increases. which of the following
     are the reasons for it?
     1) Gas molecules exert more force on each other than before.
     2) Gas molecules move faster than before and strike the walls of the container more often.
     3) Each impact of the gas molecules on the walls of the container yields a greater force than before.
     4) Impacts are now distributed over a smaller area.
     (a) 1, 2 and 3
     (b) 1, 3 and 4
     (c) 2 and 4
     (d) 2 and 3
Ans: (d)
169. Which of the following statements are correct?
          1) Teflon and dacron are polymers.
          2) Neoprene is synthetic rubber.
          3) Polythene is polyethylene polymer.
          4) Natural rubber is chloroprene.
     (a) 1, 2 and 3
     (b) 1, 2 and 4
     (c) 2, 3 and 4
     (d) 1, 3 and 4
Ans: (a)
170. Arrange the following discoveries in chronological order:
          1) Radium
          2) Oxygen
          3) Deuterium
          4) Laser
     (a) 1, 2, 3, 4
     (b) 4, 3, 2, 1
     (c) 3, 2, 1, 4
     (d) 2, 1, 3, 4
Ans: (d)
171. Water softening is the process in which:
          1) impurities are removed from water.
          2) dissolved calcium ions are removed from hard water.
          3) dissolved magnesium ions are removed from hard water.
          4) water is boiled for extracting all salts from it.
     (a) 1 and 2
     (b) 2 and 3
     (c) 1 and 4
     (d) 1, 2 and 4
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