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In a flask colourless N2O4 is in equilib...

In a flask colourless `N_2O_4` is in equilibrium with brown coloured `NO_2`. 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, `DeltaH` for this system is

A

negative

B

positive

C

zero

D

not defined

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The correct Answer is:
D
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