In a flask, colourless is in equilibrium with brown coloured . At equilibrium, when the flask is heated at 373 K, the brown colour deepens and on cooling it becomes less coloured. The change in enthal

Question

In a flask, colourless $N_2O_4$ is in equilibrium with brown coloured $NO_2$. At equilibrium, when the flask is heated at 373 K, the brown colour deepens and on cooling it becomes less coloured. The change in enthalpy for this reaction is

Prashant Kotian · Accepted Answer

Correct answer: B. The reaction is (g) ⇌ 2(g). Since heating the flask at 373 K deepens the brown colour (indicating an increase in the concentration of ), the equilibrium shifts in the forward direction. According to Le Chatelier's principle, an increase in temperature shifts the equilibrium in the direction of the endothermic reaction. Therefore, the forward reaction is endothermic, and the enthalpy change (ΔH) is positive.

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