In a flask, colourless N₂O₄ is in equilibrium with brown coloured NO₂. At equilibrium, when the flask is heated at 100°C the brown colour deepens and on cooling it becomes less coloured. The change in

Question

In a flask, colourless N₂O₄ is in equilibrium with brown coloured NO₂. At equilibrium, when the flask is heated at 100°C the brown colour deepens and on cooling it becomes less coloured. The change in enthalpy, ΔH, for the system is

Prashant Kotian · Accepted Answer

Correct answer: B. Heating the flask deepens the brown colour, indicating that high temperature favours the forward reaction (formation of NO₂). Since increasing temperature favours endothermic reactions, the forward reaction must be endothermic, meaning ΔH is positive. Therefore, correct answer is B.

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