Question

Although both CO₂ and H₂O are triatomic molecules, the shape of H₂O molecule is bent while that of CO₂ is linear. Explain this on the basis of dipole moment.

Answer 1

In CO₂, there are two C=O bonds. Each C=O bond is a polar bond.

The net dipole moment of CO₂ molecule is zero. This is possible only if CO₂ is a linear molecule. (O=C=O). The bond dipoles of two C=O bonds cancel the moment of each other.

Whereas, H₂O molecule has a net dipole moment (1.84 D). H₂O molecule has a bent structure because here the O—H bonds are oriented at an angle of 104.5° and do not cancel the bond moments of each other.

Answer 2

According to experimental results, the dipole moment of carbon dioxide is zero. This is possible only if the molecule is linear so that the dipole moments of C–O bonds are equal and opposite to nullify each other.

Resultant μ = 0 D

H₂O, on the other hand, has a dipole moment value of 1.84 D (though it is a triatomic molecule as CO₂). The value of the dipole moment suggests that the structure of H₂O molecule is bent where the dipole moment of O–H bonds are unequal.