Question

The energy required to excite the electron in the atom from $ n=1 $ to $ n=2, $ , when the ionisation enthalpy of hydrogen atom is $ 1.312\times {{10}^{6}}J $ /mol will be (in the unit of $ {{10}^{5}} $ ).

• A. 8.53
• B. 7.51
• C. $ 8.92 $
• D. 9.86

Answer 1

Answer: (D)

$ {{E}_{2}}=\frac{-1.312\times {{10}^{6}}\times {{(1)}^{2}}}{{{(2)}^{2}}} $ $ \text{=-3}\text{.28 }\!\!\times\!\!\text{ 1}{{\text{0}}^{\text{5}}}\text{J/mol} $
$ {{\text{E}}_{\text{1}}}\text{=-1}\text{.312 }\!\!\times\!\!\text{ 1}{{\text{0}}^{\text{6}}}\text{J/mol} $
$ \therefore $ $ \Delta E={{E}_{2}}-{{E}_{1}} $
$ =-3.28\times {{10}^{6}}-(1.312\times {{10}^{6}}) $
$ \text{= 9}\text{.84 }\!\!\times\!\!\text{ 1}{{\text{0}}^{\text{5}}}\text{J/mol} $