Question

An element a reacts with water to form a compound b which is used in white washing. The compoundb on heating forms an oxide which on treatment with water gives back

b. Identify a, b and c andgive the reactions involved.

Answer 1

a is Calcium

b is Calcium Hydroxide

c is Calcium oxide

Reactions

Ca+H20=Ca(Oh)2

Ca(OH)2= CaO +Co3

Answer 2

Element A is calcium (Ca). When it reacts with water, it forms calcium hydroxide. Thus, compound B is calcium hydroxide [Ca(OH)2], which is used in white Washing

Ca(s) + 2H2O(l)

Compound B on heating gives CaO.

Ca(OH)2(aq) + H2(g)

Thus, C is calcium oxide (CaO).

C(CaO) on treatment with water gives back B [Ca(OH)2].

Ca(OH)2 +Heat ----> CaO + H2O