Question

Assertion: $N_2$ is less reactive than $P_4$.
Reason: Nitrogen has more electron gain enthalpy than Phosphorus.

• A. Both assertion and reason are wrong statements.
• B. Assertion is wrong but reason is correct statement
• C. Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion.
• D. Both assertion and reason are correct statements, and reason is the correct explanation of the assertion.
• E. Assertion is correct but reason is wrong statement

Answer 1

The correct option is E Assertion is correct but reason is wrong statement

Analysing the assertion

$N_2$ is less reactive than $P_4$.
In $N_2$, triple bond is present between nitrogen atoms due to which the $N_2$ molecule has a high bond dissociation energy.
Thus, due to high bond strength, $N_2$ is highly inert and thus less reactive.
On the other hand, in $P_4$ molecules, Phosphorus has bonds with unstable angle strains which make $P_4$ highly unstable and thus more reactive.

Hence, $N_2$ is less reactive than $P_4$.
So, the assertion is correct.


Analysing the reason

Electron gain enthalpy decreases as size increases. Thus, as nitrogen is smaller than phosphorus, its electron gain enthalpy should be more than phosphorus.
But, on adding one electron to nitrogen the electron crowding increases due to which interelectronic repulsions increases. Therefore, energy is required to add electron to nitrogen and thus nitrogen has positive value of electron gain enthalpy.

On the other side, phosphorus has a comparatively larger size. So, it can accept the electron more easily as compared to nitrogen.
Hence, nitrogen has less electron gain enthalpy than phosphorus.
So, the reason is incorrect.

Hence, assertion is correct while the reason is incorrect.

Hence, option (C) is correct.