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2000 · Q124Science & TechnologyChemistrymoderate

Consider the following statements: Hard water is not suitable for I. Drinking. II. Washing clothes with soap. III. Use in boilers. IV. Irrigating crops. Which of these statements are correct?

  1. (a)I and III
  2. (b)II and III
  3. (c)I, II and IV
  4. (d)I, II, III and IV
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Official answer(b) II and III

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