(b) are always in motion
     (c) move only when struck by other molecules
     (d) are usually closer together in a gas than in a liquid
Ans: (b)
106. An atom has 17 electrons, 17 protons, 18 neutrons. Therefore which of the following is/are true?
          1) Its atomic number is 17.
          2) Its mass number is 35.
     (a) 1 only
     (b) 2 only
     (c) 1 and 2
     (d) Neither 1 nor 2
Ans: (c)
107. All acids contain the element:
     (a) hydrogen
     (b) chlorine
     (c) oxygen
     (d) sulphur
Ans: (a)
108. The difference between explosion and combustion is that:
     (a) combustion takes place only in air while an explosion can occur even without air
     (b) combustion is accompanied by loss of heat while an explosion is accompanied by absorption of heat
     (c) combustion is a chemical reaction while an explosion is caused by physical factors
     (d) there is rapid increase of pressure in confined spaces in case of an explosion, but no such change occurs during
Ans: (d)
109. Match the following:
     A. Pure water from the sea        1. Sublimation
     B. Gasoline from crude oil        2. Evaporation
     C. Table salt from sea water      3. Distillation
     D. Purified camphor               4. Fractional distillation
          A          B        C        D
     (a)  2          3        4        1
     (b)  4          3        2        1
     (c)  3          4        2        1
     (d)  4          3        1        2
Ans: (c)
110. Consider the following statements: Ammonia is: [CDS 1999]
     1) readily soluble in water
     2) used as a refrigerant
     3) used for preparation of polypropylene
     4) used as an additive in cooking gas
     Which of these statements are correct?