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
281. Which among the following is a solid non-metal?
282. On chemical analysis, a bottle cork is found to contain primarily
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
284. Which among the following gases present in the air discolours brass nameplates?
(a) Hydrogen Sulphide
285. Which one of the following is used in dry cleaning of garments?
(c) diesel oil
(d) lubricating oil
286. The main constituent of gobar gas is
287. Sulphur is readily soluble in
(d) Sodium chloride solution