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 of `NO_(2)`
D. oxidation by atmospheric `O_(2)` and formation of `NO_(2)`

Answer

B

Explanation

Pure `HNO_(3)` is highly 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 imparts yellow colour.
`4HNO_(3) to 2H_(2)O + 4NO_(2) + O_(2)`