Question

In the HCl molecule, the separation between the nuclei of the two atoms is about 1.27 Å (1 Å = 10–10 m). Find the approximate location of the CM 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.

Answer 1

H --------------Cl

let at r distance from H Center of mass exist of the system .
where total distance between H and Cl is 1.27 A°

now,
let H is origin in this system co-ordinate

CM ={mx 0 + 35.5m( 127A°)}/(m+35.5m)

= {35.5 × 127 }/36.5 A° distance from H atom

I.e CM = 123.52 A° distance from H-atom

Answer 2

hydrogen molecule is at origin RH=0
chlorine molecule is at distance 1.27A° RCl=1.27A°
hence,
Xcm=MH(0)+MCl+(1.27)/36.5
=0+35.5×1 .27/36.5
=1.24A°

hope this may help☺