Question

In the HCl molecule, separation between the nuclei of two atoms is about $1.46\stackrel{\circ }{\text{A}}$. Mass of chlorine atom is about $35.5$ times as massive as hydrogen atom and nearly all mass is concentrated at its nucleus. The distance of centre of mass from hydrogen atom is

• A. $1.42\stackrel{\circ }{\text{A}}$
• B. $0.67\stackrel{\circ }{\text{A}}$
• C. $0.96\stackrel{\circ }{\text{A}}$
• D. $0.73\stackrel{\circ }{\text{A}}$

Answer 1

The correct option is A $1.42\stackrel{\circ }{\text{A}}$


Position of centre of mass from origin
$X_{cm}=\frac{m_1{x}_1+m_2{x}_2}{m_1+m_2}=\frac{m_1\left(0\right)+m_2\left(d\right)}{m_1+m_2}$
$\because m_2=35.5m_1$
$\therefore X_{cm}=\frac{35.5\times 1.46}{(35.5+1)}$
$X_{cm}=1.42\stackrel{\circ }{\text{A}}$