Question

On the basis of dipole moment explain why co2 is linear while h2o is bent in shape though both are triatomic molecules.

Answer 1

Dipole moment is the product of the magnitude of the positive or negative charge (q) & the distance (d) between the charges,i.e



μ = q x d.

The SI unit is coulomb metre.The molecule with symmetrical & linear geometries have zero dipole moment because they are vector in nature & the dipole of different bonds cancel with one another. CO2 is symmetrical & has dipole moment 0.Therefore it will have a linear shape with bond angle 180°.



Resultant μ = 0 D

 

H2O is a unsymmetrical molecule & bent geometries, the geometries have specific dipole moment (1.84D) because the bond polarities do not cancel each other. Therefore H2O will have a bent structure with bond angle 104°.



Answer 2

Answer :

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

The net dipole moment of C02 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.

$\rule{200}{2}$