In an experiment, `NO_(2)` gas is prepared and taken into 3 test tubes X,Y and Z. `NO_(2)` gas which is brown in colour dimerises into `N_(2)O_(4)` which is colourless. Test tube X is kept at roop temperature, Y is kept in ice and Z is kept in hot water. What colour changes will you observe in the test tubes and why
`underset("Broun")(2NO_(2(g)))hArrunderset("Colourless")(N_(2)O_(4(g))),DeltaH=-57.2"kJ mol"^(-1)`

Options

A. a. In test tube X, brown colour intensifies since backward reaction is favoured at low temperature.
B. b.In test tube Y, brown colour intensifies since backward reaction takes place at roop temperature.
C. c. In test tube Z, brown colour intensifies since high temperature favours the backward reaction.
D. d. Brown colour of test tubes X,Y and remains same since there is no effect of change in temperature on the reaction .

Answer

C

Explanation

It is an exothermic reaction, hance the forward reaction is favoured at temperature which means colourless `N_(2)O_(4)` will be formed resulting in decrease in intensity of brown colour. High temperature favours backward reaction resulting in formation of `NO_(2)`. thus intensifying brown colour.