In the HCl molecule, the separation between the nuclei of the two atoms is about 1.27∘A (1 ∘A=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.
The given situation can be shown as:
Distance between H and Cl atoms =1.27∘A
Mass of H atom = m
Mass of Cl atom = 35.5m
Let the centre of mass of the system lie at a distance x from the Cl atom.
Distance of the centre of mass from the H atom = (1.27 - x)
Let us assume that the centre of mass of the given molecule lies at the origin. Therefore,
we can have:
−m(1.27−x)+35.5 mxm+35.5 m=0m(−1.27+x)+35.5 mx=0−1.27+x=−35.5 x∴ x=1.27(35.5+1)=0.0345 ∘A
Hence, the centre of mass of the HCl molecule lies 0.0345 ∘A from the Cl atom.