Q. The ionisation enthalpy of hydrogen atom is $1.312 \times 10^{6}Jmol^{- 1}$. The energy required to excite the electron in the atom from $n_{1} = 1\ to\ n_{2} = 2$ is
A) $8.51 \times 10^{5\ }J\ mol^{- 1}$
B) $6.56 \times 10^{5}\ J\ mol^{- 1}$
C) $7.56 \times 10^{5}\ J\ mol^{- 1}$
D) $9.84 \times 10^{5}\ J\ mol^{- 1}$
Explanation
(d)
Ionisation enthalpy of hydrogen atom is $1.312 \times 10^{6}J\ mol^{- 1}$.
It suggests that the energy of electron in the ground state (first orbit) is $- 1.312 \times 10^{6}\ J\ mol^{- 1}$.
$\mathrm{\Delta}E = E_{2} - E_{1}$
$\ \ \ \ \ \ \ = \left( \frac{- 1.312 \times 10^{6}}{2^{2}} \right)—\left( \frac{- 1.312 \times 10^{6}}{1} \right)$
$= 9.84 \times 10^{5}\ J\ mol^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.