In the `HCI` molecule, the separation between the nuclei of the two atoms is about `1.27Å (1Å = 10^(-10)m)`. Find the approximate location of the c.m of the molecule, given that a chlorine atom is about `35.5` times as massive as a hydrogen atom and nearly all the mass of an atom is concentrated in its nucleus ?

Explanation

As shown in Fig, suppoise the H nucleus is located at the origin. Then
`x_(1) =0, x_(2) = 1.27 Å, m_(1) =1, m_(2) = 35.5`
The position of the CM of HCl molecule is
`x= (m_(1)x_(1) + m_(2)x_(2))/(m_(1) + m_(2))`
`=(1 xx 0 + 35.5 xx 1.27)/(1 + 35.5) = 1.239 Å`
Thus the CM of HCl is located on the line joining H and Cl nuclei at a distance of `1.235 Å` from the H nucleus.