Answer the question on the basis of passage given below:
Nitrogen forms a large number of oxoacids such as \(H_2N_2O_2\) (hyponitrous acid), \(HNO_2\) (nitrous acid) and \(HNO_3\) (nitric acid). Amongst these, \(HNO_3\) is the most important. It is used in the manufacture of ammonium nitrate for fertilisers and other nitrates for use in explosives. It is also used to prepare many important organo-nitro compounds like nitroglycerine, trinitrotoluene etc. It acts as a strong oxidizing agent and used as an oxidiser in rocket fuels.
Nitrogen gas is inert at room temperature because
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Nitrogen atoms form a triple bond in nitrogen gas which has a very high bond enthalpy.
Nitrogen gas consists of \( \ce{N2} \) molecules in which the two atoms are joined by a triple bond (one σ and two pπ–pπ bonds), N≡N. Its bond enthalpy is very high, about 941.4 kJ mol−1, so a great deal of energy is needed to break the molecule before it can react. That is why dinitrogen is rather inert at room temperature; its reactivity rises quickly at high temperature, when it forms nitrides with metals such as lithium and magnesium.
Why the other options are incorrect
Option (1) Nitrogen has lone pair of electrons on it. — Incorrect. Each N atom in \( \ce{N2} \) does carry a lone pair, but a lone pair makes a molecule more able to react (as in \( \ce{NH3} \)), not less.
Option (2) Nitrogen atom has very small size. — Incorrect. The small size is what allows strong pπ–pπ multiple bonding, but size by itself does not make a substance inert; the deciding factor is the strong triple bond.
Option (4) Nitrogen atom does not contain any d orbital in its outermost shell. — Incorrect. The absence of d orbitals limits the covalency of nitrogen to four; it does not explain why \( \ce{N2} \) is unreactive.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Dinitrogen – “… Dinitrogen is rather inert at room temperature because of the high bond enthalpy of N≡N bond. Reactivity, however, increases rapidly with rise in temperature.”