Question

CO₂ and H₂O both are triatomic molecule but their dipole moment values are different. Why?

Answer 1

1. A linear form of carbon dioxide has zero dipole moment. In CO₂ the dipole moment of two polar bonds are equal in magnitude but have opposite directions. Hence, the net dipole moment of the CO₂ molecule is
   µ = µ₁ + µ₂
   µ = µ₁ + (- µ₁) = 0
   In this case `mu = vec mu_1 + vec((- mu_1) = 0`
2. But in the case of water, net dipole moment is the vector sum µ₁ + µ₂ as follows:
   
   
   

   Dipole moment in water is found to be 1.85 D.

3. CO₂ and H₂O both are triatomic molecules but their dipole moment values are zero and 1.85 D respectively.