Question

The energy absorbed by each molecule $\left(A_2\right)$ of a substance is $4.4\times {10}^{-19}J$ and bond energy per molecule is $4.0\times {10}^{-19}J$. The kinetic energy of the molecule per atom will be :

• A. $4.0\times {10}^{-20}J$
• B. $2.0\times {10}^{-20}J$
• C. $2.2\times {10}^{-19}J$
• D. $4\times {10}^{-19}J$

Answer 1

The correct option is B $2.0\times {10}^{-20}J$

$\text{K.E. per atom}=\frac{\text{energy absorbed}-\text{bond energy}}{\text{no. of atoms}}$

As it is given in question that the molecule is $A_2$, i.e., diatomic.

$\therefore \text{K.E. per atom}=\frac{4.4\times {10}^{-19}-4.0\times {10}^{-19}}{2}=\frac{0.4\times {10}^{-19}}{2}=0.2\times {10}^{-19}=2.0\times {10}^{-20}J$

Hence, the kinetic energy of the molecule per atom will be $2.0\times {10}^{-20}$

So, the correct option is $B$