When a vapour, at atmosphere pressure was gradually heated from `25^(circ)C` its colour wasa found to deepen at first and then to fade as the temperature was raised above `160^(circ)C`. At `600^(circ)C`, the vapour was almost colourless, but its colour deepended when the pressure was raised at this temperature. The vapour was:

Options

A. the bromine.
B. a mixture of nitrogen dioxide and dinitrogen tetraoxide.
C. pure nitrogen dioxide .
D. pure dinitrogen tetraoxide.

Answer

B

Explanation

`underset("Colourless")(N_(2)O_(2)(g))overset(160^circC)hArrunderset(Brown)(2NO_(2))overset(600^circC)hArrunderset(("Colourless"))(2NO_(2)+O_(2))`
As the conersion of NO and `O_(2)` is accomained by decrease in number of moles of agases ( from 3 to 2) it is favoured by high pressure. Thus incresing pressure at `600^(circC)` shifts the equilibrium in the backward direction and this leads to the formation of `NO_(2)`- a brown coloured gas. Thus original vapour was `N_(2)O_(2)` or dinitrogen tetraoxde.