question_answer 20)

    An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change?                 (a) Baking powder                                                           (b) Lime                 (c) Ammonium hydroxide solution                           (d) Hydrochloric acid                

Answer:

  (d) Since, the aqueous solution turns red litmus solution blue. So, it is a basic compound. An acid solution (HCI) would reverse the change. That is HCI would turn blue litmus solution to red. Other options baking powder, lime and ammonium hydroxide solution are basic compounds. So, the blue litmus solution would not change the colour by adding these compounds.