Pure `HNO_(3)` is colourless, howerver, it gradually becomes yellow on standing due to _______ .

Options

A. the decomposition of `HNO_(3)` and formation of NO.
B. the decomposition of `HNO_(3)` and formation of `NO_(2)`.
C. oxidation by atmospheric `O_(2)` and formation NO.
D. oxidation by atmospheric `O_(2)` and formation of `NO_(2)`.

Answer

B

Explanation

Pure `HNO_(3)` is highlly unstable which undergoes decomposition giving `H_(2)O, O_(2) "and" NO_(2)* NO_(2)` is a reddish brown gas dissolves in `HNO_(3)` and impart yellow colour.
`4HNO_(3) rarr 2H_(2)O + 4NO_(2) + O_(2)`