Dipole Moment Formula
Measure of molecular polarity
Formula
μ = q × d
- μ = dipole moment (C·m or D)
- q = magnitude of charge (C)
- d = distance between charges (m)
- 1 Debye (D) = 3.336 × 10⁻³⁰ C·m
Example
Given: q = 1.6 × 10⁻¹⁹ C (electron charge), d = 1.0 × 10⁻¹⁰ m.
μ = (1.6 × 10⁻¹⁹) × (1.0 × 10⁻¹⁰) = 1.6 × 10⁻²⁹ C·m
μ = (1.6 × 10⁻²⁹) / (3.336 × 10⁻³⁰) ≈ 4.8 D
Answer: μ ≈ 4.8 D
Common Mistakes
Ignoring vector nature
For polyatomic molecules, sum bond dipoles as vectors.
Symmetry cancellation
Symmetric molecules like CO₂ have μ = 0 despite polar bonds.
FAQ
What molecules have zero dipole moment?
Homonuclear diatomics (H₂, O₂) and symmetric structures (CH₄, CO₂, BF₃).
How does polarity affect solubility?
Higher μ generally means better solubility in polar solvents like water.