Question

What changes will result in a loss of color for the following reaction?

N₂O₄(g) -> 2NO₂(g) dH < 0

<-

colorless brown

I. Increasing temperature

II. Decreasing volume

III. Addition of No2.

Answer 1

This can be explained by le chatelier principle

N₂O₄(g) -> 2NO₂(g)

for this reaction, dH is negative which means the reaction is exothermic in nature in the forward direction.

I) when temperature increasing the equilibrium goes to that direction in which temperature decreases according to le chatelier principle. that is possible only when the equilibrium shifts towards the left side which means loss of color occurs.

II) When volume decreases the system goes to that side in which the volume increases. That is possible only when the system goes towards the left side which means loss of colors.

III) The addition of NO2 increases the concentration on the right side. so the system goes towards the left side in order to decreases the concentration. the equilibrium shifts towards the left side which mean loss of colors.

So in all cases i.e. I, II, III  loss of color occurs.