Systems of Particles and Rotational Motion

Let C.M. be at a distance x Å from H-atom
Distance of C.M. from Cl atom =(1.27–x)Å
Let the mass of H-atom = m units
The mass of the Cl-atom = 35.5 m units
If C.M. is taken at the origin, then
mx+(1.27–x)35.5m=0
mx=–(1.27–x)35.5m
Negative sign indicatesthat if Cl atom is on the right side of C.M.(+), the hydrogen atom is on the left side of C.M. So, avoiding, if we get
x+35.5x=1.27×35.5
36.5x=45.085
x=

45.005

36.5

=1.235Å
Therefore, the centre of mass located on theline joining H and Cl nuclei at a distance of 1.24 Å from the H atom.