A solution of a substance ‘X’ is used for white washing. (i) Name the substance ‘X’ and write its formula. (ii) Write the reaction of the substance ‘X’ named in (i) above with water.

A: (i) The substance ‘X’ used for white washing is Quicklime or Calcium Oxide, and its chemical formula is CaO. (ii) When Calcium Oxide (CaO) reacts with water (H2O), it forms Calcium Hydroxide (Ca(OH)2). The reaction is as follows: CaO+H2​O→Ca(OH)2 This is called the slaking of lime and the product, Calcium Hydroxide, is used for white washing because it reflects sunlight well, making buildings appear bright white.