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 addition of dilute HNO${}_3$ to unknown metal (2) produced an orange gas. Which of the following is the orange gas?

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

Answer 1

The correct option is E NO${}_2$

The addition of dilute $HN{O}_3$ to unknown metal (2) (silver metal) produced an orange gas nitrogen dioxide $\left(N{O}_2\right)$.
Note: Various gases have following colours.
$C{l}_2-$ green
$H_2-$ colorless
$O_2-$ colorless
$C{O}_2-$ colorless
$N{O}_2-$ orange/brown