Question
Among H _ 2 ~S , H _ 2 O , NF _ 3 , NH _ 3 and CHCl _ 3 , identify the molecule ( X ) with lowest dipole moment value. The number of lone pairs of electrons present on the central atom of the molecule (X) is :
JEE Main
Chemistry
Chemical Bonding and Molecular Structure
2026
JEE Main 2026 (22 January Shift 2)
JEE Main Chemistry Question (2026) — Solution
Options
- A. 0
- B. 3
- C. 2
- D. 1
Answer
D. 1
Step-by-step solution
Comparing dipole moments: H_2S ≈ 0.97 D (bent, 2 lone pairs on S), H_2O ≈ 1.85 D (bent, 2 lone pairs on O), NF_3 ≈ 0.24 D (pyramidal, 1 lone pair on N), NH_3 ≈ 1.42 D (pyramidal, 1 lone pair on N), CHCl_3 ≈ 1.04 D (tetrahedral, 0 lone pairs on C). NF_3 has the lowest dipole moment because the highly polar N-F bonds are oriented in such a way that their contributions nearly cancel with the effect of the lone pair. The central atom in NF_3 is N, which has 1 lone pair of electrons.
Related: Chemistry — Chemical Bonding and Molecular Structure · All PYQ Banks