JEE Chemistry 2023 Question with Solution

Given: Four statements about $\mathrm{NF_3}$, $\mathrm{N_2}$, $\mathrm{O_2}$, isoelectronic species, and dipole moment are to be checked.

Find: Which pair of statements is correct.

Step 1: Analysis of Statement (A).

The $\mathrm{NF_3}$ molecule has three bond pairs and one lone pair on nitrogen. Due to the presence of a lone pair, its geometry is trigonal pyramidal, not trigonal planar.

Hence, Statement (A) is incorrect.

Step 2: Analysis of Statement (B).

The bond order of $\mathrm{N_2}$ is $3$, while the bond order of $\mathrm{O_2}$ is $2$. Higher bond order corresponds to shorter bond length.

Therefore, the bond length of $\mathrm{N_2}$ is shorter than that of $\mathrm{O_2}$.

Hence, Statement (B) is correct.

Step 3: Analysis of Statement (C).

Isoelectronic molecules or ions have the same number of electrons and similar electronic configurations, which generally results in identical bond order.

Hence, Statement (C) is correct.

Step 4: Analysis of Statement (D).

Water ($\mathrm{H_2O}$) has a higher dipole moment than $\mathrm{H_2S}$ due to greater electronegativity difference between oxygen and hydrogen compared to sulfur and hydrogen.

Hence, Statement (D) is incorrect.

Step 5: Conclusion.

Only Statements (B) and (C) are correct. Therefore, the correct option is B.

Quick Tip: Higher bond order means stronger and shorter bonds, and lone pairs significantly affect molecular geometry and dipole moment.