Q51 / 200 · NEET 2009 (Screening) · Chemistry

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

  • Correct answer
    A
    $2.0 \times 10^{-20} \mathrm{~J}$
  • B
    $2.2 \times 10^{-19} \mathrm{~J}$
  • C
    $2.0 \times 10^{-19} \mathrm{~J}$
  • D
    $4.0 \times 10^{-20} \mathrm{~J}$

Solution

$K E$ of molecule $=$ energy absorbed by molecule - BE per molecule $$ \begin{aligned} & =\left[\left(4.4 \times 10^{-19}\right)-\left(4.0 \times 10^{-19}\right) \mathrm{J}\right. \\ & =0.4 \times 10^{-19} \mathrm{~J} \\ & \text { KE per atom }=\frac{0.4 \times 10^{-19}}{2} \mathrm{~J}=2.0 \times 10^{-20} \mathrm{~J} \end{aligned} $$

Hence, the correct answer is option: 'A'.

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