Consider the following list of molecules: BeF ₂, BF ₃, H ₂ O , NH ₃, CCl ₄, CHCl ₃, H ₂ S , PCl ₅ How many of the given molecules have a net dipole moment of exactly zero?

Step-by-step solution

To determine the net dipole moment, we must analyze the geometry and symmetry of each molecule. BeF ₂ : Linear geometry, highly symmetrical. The two Be - F bond dipoles cancel each other out ( = 0 ). BF ₃ : Trigonal planar geometry, symmetrical. The vector sum of the three B - F bond dipoles is zero ( = 0 ). H ₂ O : Bent geometry with two lone pairs on oxygen. The bond dipoles and lone pair dipoles do not cancel ( 0 ). NH ₃ : Trigonal pyramidal geometry with one lone pair. The dipoles reinforce each other ( 0 ). CC