KCET 2026 Chemistry Solved Paper

Concept:We need to identify which given order does not match the actual trend of the property mentioned for each species.Explanation:For (a), $\mathrm{BF}_{3}$ is trigonal planar and symmetrical, so its dipole moment is zero.$\mathrm{NH}_{3}$ has a larger dipole moment than $\mathrm{NF}_{3}$ because in $\mathrm{NF}_{3}$, the bond dipoles oppose the lone-pair effect.Therefore, the correct dipole moment order is $\mathrm{NH}_{3} > \mathrm{NF}_{3} > \mathrm{BF}_{3}$.The given order is $\mathrm{BF}_{3} > \mathrm{NF}_{3} > \mathrm{NH}_{3}$, which is incorrect.For (b), $\mathrm{HgCl}_{2}$ is linear with bond angle $180^{\circ}$, $\mathrm{NH}_{4}^{+}$ is tetrahedral with bond angle $109.5^{\circ}$, and $\mathrm{SF}_{6}$ is octahedral with bond angle $90^{\circ}$.Thus, $\mathrm{HgCl}_{2} > \mathrm{NH}_{4}^{+} > \mathrm{SF}_{6}$ agrees with the property.For (c), hydrogen-bonding strength increases with electronegativity: $\mathrm{N} < \mathrm{O} < \mathrm{F}$.Hence, $\mathrm{NH}_{3} < \mathrm{H}_{2}\mathrm{O} < \mathrm{HF}$ is correct.For (d), bond length increases down the halogen group: $\mathrm{Cl} < \mathrm{Br} < \mathrm{I}$.Hence, $\mathrm{H-I} > \mathrm{H-Br} > \mathrm{H-Cl}$ is correct.Only option (a) disagrees with the indicated property.Answer:Option B: a only