Question

1. The dipole moment of BeF is zero, while that of H2O is 1.85 D.
Account for this on the basis of their molecular structure.
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Answer 1

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Answer 2

The dipole moment of $\bf BeF_2$ is 0 while that of $\bf H_2O$ is 1.85 D is because of the following reasons.

• The hybridization of $BeF_2$  is sp and hence it is linear in shape with Be as the centre atom.

• The polarity of each Be-F bond acts in opposite direction and it is linear, the effect gets cancelled out completely hence its dipole moment is zero.

• The hybridization of $H_2O$ is $sp^3$ and has a bent shape due to two bonds and a lone pair.

• The polarity of each H-O bond is in opposite direction but as the angle between the bonds is not 180, the effect is not completely cancelled and hence the resultant dipole moment is 1.85 D.

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