Question

Assertion: Nitrogen in unreactive at room temperature but becomes reactive at elevated temperatures (on heating, or in the presence of a catalysts).

Reason: In nitrogen molecule, there is extensive delocalisation of electrons.

• 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. Both Assertion and Reason are incorrect

Answer 1

The correct option is C Assertion is correct but Reason is incorrect

There is no delocalisation of electrons in $N_2$ molecule but its electrons are involved in triple bond formation and remaining electrons are available as one lone pair on each $N$ atom. In a reaction, there is a requirement of older bond to break so that new bonds would be formed. But breaking bond in $N_2$ need very high amount of activation energy which is not available at ordinary temperature. So, it is almost inert at room temperature. But at higher temperature, it is easier to break $N\equiv N$ bond in $N_2$. Therefore, it becomes reactive at elevated temperatures.
Hence, option (d) is the correct answer.