Question

Assertion :On cooling, the brown colour of nitrogen dioxide disappears. Reason: On cooling $N{O}_2$ undergoes dimerisation resulting in the pairing of odd electrons of $N{O}_2$.

Read the above assertion and reason and choose the corret option regarding it.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

At low pressures or at high temperatures, ${NO}_2$ has a deep brown colour, but at low temperatures the colour almost completely disappears as NO2 dimerizes to form dinitrogen tetroxide, $N_2{O}_4$. At room temperature an equilibrium between the two molecules exists.