Number of non polar molecules given following. H₂O, SO₂, BF₃, H₂, CHCl₃

The correct answer is 2.

To determine the number of non-polar molecules from the given list, we need to analyze their molecular geometry and net dipole moment ($\mu$). A molecule is non-polar if its individual bond dipoles cancel each other out, resulting in a net dipole moment of zero ($\mu =0$). If there is a net separation of charge, the molecule is polar ($\mu \ne 0$).

Let's examine each molecule step-by-step:

1. H₂O (Water):
Water has a bent molecular geometry due to the presence of two lone pairs on the central oxygen atom. The individual polar O-H bond dipoles reinforce each other rather than canceling, leading to a net dipole moment:
$\mu \ne 0$
Therefore, H₂O is a polar molecule.

2. SO₂ (Sulfur Dioxide):
Sulfur dioxide has a bent geometry due to the presence of one lone pair on the sulfur atom. The polar S-O bonds are angled and their dipoles do not cancel out:
$\mu \ne 0$
Therefore, SO₂ is a polar molecule.

3. BF₃ (Boron Trifluoride):
Boron trifluoride has a symmetrical trigonal planar geometry. The three highly polar B-F bonds are oriented at 120° angles to each other in a single plane. Because of this perfect symmetry, the vector sum of the three bond dipoles cancels out completely:
$\mu =0$
Therefore, BF₃ is a non-polar molecule.

4. H₂ (Hydrogen gas):
Hydrogen is a homonuclear diatomic molecule. Since both hydrogen atoms have identical electronegativities, there is no unequal sharing of electrons and no bond dipole:
$\mu =0$
Therefore, H₂ is a non-polar molecule.

5. CHCl₃ (Chloroform):
Chloroform has a tetrahedral geometry, but it is asymmetrical because it contains one C-H bond and three C-Cl bonds. The highly electronegative chlorine atoms pull electron density away from the carbon, and these dipoles do not cancel out, resulting in a net dipole moment:
$\mu \ne 0$
Therefore, CHCl₃ is a polar molecule.

Conclusion:
Among the given molecules, BF₃ and H₂ are non-polar. Thus, the number of non-polar molecules is 2.