2021 H2 Chem P1 Q6 — Chemical bonding Solution

The answer is D (trichloromethane, tetrahedral, polar).

D ✓: \(\text{CHCl}_3\) has 4 bond pairs and no lone pair around C, so it is tetrahedral. The C-H and C-Cl bond dipoles are not the same, so the dipoles do not cancel and the molecule is polar.

A ✗: \(\text{BCl}_3\) has 3 bond pairs and no lone pair around B, so it is trigonal planar. The three identical B-Cl dipoles cancel, so the molecule is non-polar, not polar.

B ✗: \(\text{NCl}_3\) has 3 bond pairs and 1 lone pair around N, so it is trigonal pyramidal. The N-Cl bonds are almost non-polar, but the lone pair of electrons on N makes the molecule polar, not non-polar.

C ✗: \(\text{SO}_2\) has 2 bond pairs and 1 lone pair around S, so it is bent, not linear. The S=O dipoles do not cancel, so the molecule is polar, not non-polar.