MCQ
The ionisation enthalpy of hydrogen atom is $\ce{1.312 \times 10^6J mol^{-1}}$. The energy required to excite the electron in the atoms from $n = 1$ to $\ce{n_2 = 2}$ is :
  • A
    $ 6.56 \times 10^5 \mathrm{~J} \mathrm{~mol}^{-1} $
  • $9.84 \times 10^5 \mathrm{~J} \mathrm{~mol}^{-1} $
  • C
    $ 7.56 \times 10^5 \mathrm{~J} \mathrm{~mol}^{-1} $
  • D
    $ 8.51 \times 10^5 \mathrm{~J} \mathrm{~mol}^{-1}$

Answer

Correct option: B.
$9.84 \times 10^5 \mathrm{~J} \mathrm{~mol}^{-1} $
$\Delta\text{E}-\text{E}_2-\text{E}_1$
$=\Big(\frac{-1.312\times10^6}{2^2}\Big)-\Big(\frac{-1.312\times10^6}{1}\Big)$
$=9.84\times10^5\text{J mol}^{-1}$

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