280. Plaster of Paris
     (a) contracts while setting
     (b) expands while setting
     (c) is highly volatile
     (d) does not suffer any changes in volume while setting
Ans: (b)
281. Which among the following is a solid non-metal?
     (a) chlorine
     (b) mercury
     (c) water
     (d) iodine
Ans: (d)
282. On chemical analysis, a bottle cork is found to contain primarily
     (a) proteins
     (b) carbohydrates
     (c) tannins
     (d) lipids
Ans: (b)
283. Hard water does not lather well with soap because
     (a) it contains carbonates of calcium and magnesium
     (b) it contains sodium chloride
     (c) it is highly coloured
     (d) it contains suspended impurities
Ans: (a)
284. Which among the following gases present in the air discolours brass nameplates?
     (a) Hydrogen Sulphide
     (b) Nitrogen
     (c) Carbon-di-oxide
     (d) Oxygen
Ans: (c)
285. Which one of the following is used in dry cleaning of garments?
     (a) asphalt
     (b) naphtha
     (c) diesel oil
     (d) lubricating oil
Ans: (b)
286. The main constituent of gobar gas is
     (a) methane
     (b) nitrogen
     (c) carbondioxide
     (d) ethylene
Ans: (a)
287. Sulphur is readily soluble in
     (a) Water
     (b) Alcohol
     (c) Carbon-di-sulphide
     (d) Sodium chloride solution
Ans: (c)