Identify a pair of molecules having zero dipole moment.

Step-by-step solution

The dipole moment of a molecule depends on its geometry and the polarity of its bonds. BF ₃ has a symmetrical trigonal planar geometry, so its dipole moment is zero. However, HBr is a polar diatomic molecule with a non-zero dipole moment. CH ₄ has a symmetrical tetrahedral geometry, so its dipole moment is zero. NF ₃ has a trigonal pyramidal geometry with a lone pair on nitrogen, resulting in a non-zero dipole moment. NH ₃ and H ₂ O have trigonal pyramidal and bent geometries respectively, both possessing lone pair