1. Principle used

A species has non-zero dipole moment if the vector sum of all bond dipoles does not cancel due to geometry.

So, we check the shape of each molecule/species.

2. Examine each compound/species

(i) $\mathrm{BeCl_2}$

• Shape: linear
• Two identical $\mathrm{Be-Cl}$ bond dipoles are opposite and cancel.
• Dipole moment $=0$

(ii) $\mathrm{BCl_3}$

• Shape: trigonal planar
• Three identical bond dipoles cancel by symmetry.
• Dipole moment $=0$

(iii) $\mathrm{NF_3}$

• Shape: trigonal pyramidal
• Because of lone pair on N, geometry is unsymmetrical.
• Bond dipoles do not cancel.
• Dipole moment $\neq 0$

(iv) $\mathrm{XeF_4}$

• Shape: square planar
• Bond dipoles cancel due to symmetry.
• Dipole moment $=0$

(v) $\mathrm{CCl_4}$

• Shape: tetrahedral and symmetrical
• All bond dipoles cancel.
• Dipole moment $=0$

(vi) $\mathrm{H_2O}$

• Shape: bent (V-shaped)
• Bond dipoles do not cancel.
• Dipole moment $\neq 0$

(vii) $\mathrm{H_2S}$

• Shape: bent
• Bond dipoles do not cancel.
• Dipole moment $\neq 0$

(viii) $\mathrm{HBr}$

• Heteronuclear diatomic molecule
• Dipole moment $\neq 0$

(ix) $\mathrm{CO_2}$

• Shape: linear
• Two $\mathrm{C=O}$ bond dipoles cancel.
• Dipole moment $=0$

(x) $\mathrm{H_2}$

• Homonuclear diatomic molecule
• Dipole moment $=0$

(xi) $\mathrm{HCl}$

• Heteronuclear diatomic molecule
• Dipole moment $\neq 0$

3. Count species with non-zero dipole moment

Non-zero dipole moment species are:

• $\mathrm{NF_3}$
• $\mathrm{H_2O}$
• $\mathrm{H_2S}$
• $\mathrm{HBr}$
• $\mathrm{HCl}$

Total number $=5$

4. Comparison with stored answer

Stored correct answer = $5$

Our derived answer = $5$

So, the answer agrees with the stored correct answer.