(a) A substance 'X' is used as a building material and is insoluble in water. When it reacts with dil. $HCl$, it produces a gas which turns lime water milky.

(i) Write the chemical name and formula of 'X'.

(ii) Write chemical equations for the chemical reactions involved in the above statements.

OR

(b) A metal 'M' on reacting with dilute acid liberates a gas 'G'. The same metal also liberates gas 'G' when reacts with a base.

(i) Write the name of gas 'G'.

(ii) How will you test the presence of this gas ?

(iii) Write chemical equations for the reactions of the metal with (1) an acid and (2) a base.

(a) (i) The chemical name and formula of 'X' is calcium carbonate ($CaCO_3$).

(ii) The chemical equations for the chemical reactions involved in the above statements are:

$CaCO_3 + 2HCl ightarrow CaCl_2 + H_2O + CO_2$

$CO_2 + Ca(OH)_2 ightarrow CaCO_3 + H_2O$

OR

(b) (i) The name of gas 'G' is hydrogen.

(ii) To test the presence of hydrogen, we can use the burning splint test.

(iii) The chemical equations for the reactions of the metal with (1) an acid and (2) a base are:

$M + 2HCl ightarrow MCl_2 + H_2$

$M + 2NaOH ightarrow M(OH)_2 + H_2$