Question

Unknown metal	Appearance	Reactions with dilute HCl	Reaction with dilute HNO${}_3$
(1)	Dull gray solid with white oxide coating	Dissolved with bubbles of clear gas	Dissolved with bubbles of clear gas
(2)	Solid; lustrous smooth silver-gray surface	No reaction	Dissolved with bubbles of orange gas

The transparent gas is produced by the addition of dilute HCI to unknown metal (1). Which of the following represents the transparent gas ?

• A. Cl${}_2$
• B. H${}_2$
• C. O${}_2$
• D. CO${}_2$
• E. NO${}_2$

Answer 1

The correct option is B H${}_2$

When dilute $HCl$ is added to the unknown metal (1) (zinc), the transparent gas produced is hydrogen.
Note: Chlorine and $N{O}_2$ gases are green and orange coloured respectively. $C{O}_2$ is not possible as no $C$ atoms are present.
Also, metals react with acids to form hydrogen gas.