Q.1 The molecule having net ‘non-zero dipole moment’ is
(A) CCl4 (B) NF3 (C) CO2 (D) BCl3

Which Molecule Has a Net Non-Zero Dipole Moment? CCl4, NF3, CO2, or BCl3

The correct answer is (B) NF3, as it possesses a net non-zero dipole moment due to its molecular geometry and electronegativity differences. This multiple-choice question tests understanding of molecular polarity, symmetry, and vector addition of bond dipoles.​​

Option Analysis

Each option’s dipole moment depends on bond polarity (from electronegativity differences) and molecular symmetry, where individual bond dipoles either cancel (zero net μ) or add vectorially (non-zero μ).

• (A) CCl4: Tetrahedral geometry (sp³ hybridized carbon) with four identical C-Cl bonds. Electronegativity difference (Cl 3.0 > C 2.5) creates bond dipoles, but perfect symmetry causes them to cancel completely, yielding zero net dipole moment.​

• (B) NF3: Trigonal pyramidal geometry (AX3E, VSEPR) due to lone pair on nitrogen. N-F bonds are polar (F 4.0 > N 3.0), and the lone pair enhances asymmetry, resulting in a net dipole moment of about 0.24 D pointing toward the lone pair side.​

• (C) CO2: Linear geometry (O=C=O, sp hybridized carbon). C=O bonds are polar (O 3.5 > C 2.5), but opposite directions cause exact cancellation, giving zero net dipole moment.​

• (D) BCl3: Trigonal planar geometry (sp² hybridized boron). B-Cl bonds have slight polarity (Cl 3.0 > B 2.0), but 120° bond angles and symmetry cancel all dipoles, resulting in zero net dipole moment.​

Key Concept

Dipole moment (μ) is zero in symmetrical molecules like CCl4 (tetrahedral), CO2 (linear), and BCl3 (trigonal planar) due to dipole cancellation. NF3’s pyramidal shape prevents this, making it the only option with non-zero μ—crucial for exams like JEE Main.​