COMEDK 2024 Shift 2 Paper

Let's analyze each statement one by one to determine which is incorrect:
Statement A: Isoelectronic molecules/ions have the same bond order.
This statement is incorrect. While isoelectronic species have the same number of electrons, they can have different bond orders due to differences in their nuclear charges and arrangement of electrons in molecular orbitals. Therefore, isoelectronic molecules/ions do not necessarily have the same bond order.
Statement B: Dipole moment of NH3 is greater than that of NF3.
This statement is correct. In NH3, the lone pair on the nitrogen contributes to a higher dipole moment because the dipole moments of the N-H bonds point towards the nitrogen, reinforcing the overall dipole moment. In NF3, the highly electronegative fluorine atoms pull electron density away, reducing the overall dipole moment of the molecule.
Statement C: The Carbon in Methyl Carbocation is sp3 hybridised.
This statement is incorrect. The carbon in a methyl carbocation (CH3+)is sp2 hybridised because it has only three regions of electron density (three bonds and no lone pairs), forming a planar structure.
Statement D: The stability of an ionic compound is measured in terms of its lattice enthalpy and not simply based on attaining Octet configuration.
This statement is correct. The stability of an ionic compound is indeed largely determined by its lattice enthalpy, which is the energy released when ions come together to form a lattice structure. Attaining an octet configuration alone does not fully account for the stability without considering lattice enthalpy.
Given this analysis, the incorrect statements are A and C. However, since we must choose one option, we should select the first incorrect statement from the provided options.
Choice A: Isoelectronic molecules/ions have the same bond order.
The correct answer is Option A.