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2003 · Q145Science & TechnologyChemistrymoderate

Which one of the following statements is correct?

  1. (a)The presence of NaCl increases the rate of setting of Plaster of Paris
  2. (b)Gypsum is added to the cement to slow down its rate of setting
  3. (c)All alkaline earth metals form hydrated salts
  4. (d)Barium and Strontium are found free in nature
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Official answer(d) Barium and Strontium are found free in nature

2010 · Q11Science & TechnologyChemistryeasy

Chlorination is a process used for water purification. The disinfecting action of chlorine is mainly due to

  1. (a)The formation of hydrochloric acid when chlorine is added to water
  2. (b)The formation of hypochlorous acid when chlorine is added to water
  3. (c)The formation of nascent oxygen when chlorine is added to water
  4. (d)The formation of hydrogen when chlorine is added to water
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Official answer(b) The formation of hypochlorous acid when chlorine is added to water