Question

Calculate the reduced mass of $HCl$ molecule.
Given that the mass of $H$ atom is $1.0078\text{amu}$ and the mass of Cl atom is $34.9688\text{amu}$.
Note that $1\text{amu}=1.660565\times {10}^{-27}\text{kg}$.

• A. $1.627\times {10}^{-27}\text{kg}$
• B. $1.253\times {10}^{-27}\text{kg}$
• C. $1.978\times {10}^{-27}\text{kg}$
• D. $2.538\times {10}^{-27}\text{kg}$

Answer 1

The correct option is A $1.627\times {10}^{-27}\text{kg}$

Reduced mass of the molecule is
$\mu =\frac{m_1{m}_2}{m_1+m_2}$
$\mu =\frac{1.0078\text{amu}\times 34.9688\text{amu}}{1.0078\text{amu}+34.9688\text{amu}}$
$\mu =0.9796\text{amu}$

$\mu =0.9796\text{amu}\times \frac{1.660565\times {10}^{-27}\text{kg}}{1\text{amu}}=1.627\times {10}^{-27}\text{kg}$