Question

Iqbal treated a lustrous, divalent element ‘X’ first with sodium hydroxide and then with hydrochloric acid. He observed the formation of bubbles in both the cases. On testing, he found the gas to be A) Carbon dioxide B) Hydrogen C) Chlorine D) Oxygen

Answer 1

On testing, he found the gas to be B) Hydrogen.

Reason:

A lustrous divalent element clearly mentions the fact that it is a metal.

• First , the metal reacts with sodium hydroxide (a base) and later reacts with hydrochloric acid (an acid).

• In both cases, bubbles are observed in the test tube.

So, the metal has to be zinc (Zn) ;

$\sf{Zn + NaOH \rightarrow Na_{2}ZnO_{2}+H_{2}}$

$\sf{Zn + HCl \rightarrow ZnCl_{2}+H_{2}}$

• Presence of hydrogen in the test tube can be verified by bringing a burning matchstick near the evolved gas such that a small explosion with a pop sound can be seen and heard.

Hope It Helps.