When a sample of NO2 is placed in a container, this equilibrium is rapidly established.
2NO2(g) N2O4(g)
If this equilibrium mixture is a darker colour at high temperatures and at low pressure, w

Question

When a sample of NO2 is placed in a container, this equilibrium is rapidly established.
2NO2(g) $\rightleftharpoons$ N2O4(g)
If this equilibrium mixture is a darker colour at high temperatures and at low pressure, which of these statements about the reaction is true?

Prashant Kotian · Accepted Answer

Correct answer: A. Step 1: According to Le Chatelier's principle, an increase in temperature shifts the equilibrium in the endothermic direction. Since the mixture becomes darker at high temperatures, the concentration of the darker species must increase. Step 2: NO2 is a reddish-brown gas, whereas N2O4 is a colorless gas. Since the color darkens at higher temperatures, the dimerization reaction 2NO2 <=> N2O4 must be exothermic. Step 3: This confirms that the reaction is exothermic and NO2 is darker in color than N2O4, which corresponds to option (a).

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