question_answer 84)

  An element A reacts with water to form a compound B which is used in white washing. The compound B on heating forms an oxide C which on treatment with water gives back B. Identify A, B and C and give the reactions involved.

Answer:

                calcium hydroxide,which is used in white washing.                 Compound B on heating gives CaO.                 Thus, C is calcium oxide (CaO). The reactions involved are