Question

Although both $CO_{2}$ and $H_{2}O$ are triatomic molecules, the shape of $H_{2}O$ molecule is bent while that of $CO_{2}$ is linear. Explain this on the basis of dipole moment.

Answer 1

 Each bond in carbon dioxide is a polar bond hence there are two C=O bonds. Carbon dioxide molecule has the zero- dipole moment. This can be possible only if the molecule carbon dioxide belongs to the linear molecule. The linear molecule of the carbon dioxide is given by O=C=O bond.  

  The dipole moment of the two bonds C=O eliminate the moment of each other where water molecule $H_{2}O$ has the moment of dipole (1.84D). Because of O-H the $H_{2}O$ has a bent like structure which are adapted at an angle  104.5° and the moment of the bond do not get cancelled each other.