Question

( 32 9- 4 3 n=2-1=513.68 (7 ) 1 .818 3 10.2 36 10:24.882 - 13.6(7-2) = 12.88 ev 1.8g of hydrogen atoms are excited to higher energy level by certain radiation. The study of spectra indicates that 27% of the atoms are in 30 energy level and 15% atoms in 2energy level and the rest in the ground state. I.P. of H is 21.7x10-erg. Calculate the total energy evolved when all the atoms return to ground state. Terg =1075 to cibodi s tohoto OBJECTIVE the energy of an electron in the first Bohr orbit of H-atom is –313.6 Kcal/mol; then energ I) 21316 Kcal/mol

JEE/Engineering Exams

Chemistry

Solution

134

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( begin{aligned} E_{n} &=-frac{R}{n^{2}} Delta E &=Rleft(frac{1}{left.n_{j}^{2}-frac{1}{n_{1}^{2}}right)}right.end{aligned} ) If in energy requiced to remone electowngomed state of atom ( I_{1}=Rleft(frac{1}{n_{1}^{2}}-frac{1}{infty^{2}}right) underline{R}left(frac{1}{12}-0right)=2 cdot 17 times 10^{-12} mathrm{erg} ) 2. Gergy enolued for ( n=3 rightarrow 1 ) ( Delta E_{3} rightarrow E_{3}-E_{1}=Rleft(frac{1}{1^{2}}-frac{1}{3^{2}}right)=21.7 times 10^{-12} mathrm{erg} timesleft(1-frac{1}{9}right) ) ( =1.93 times 10^{-42 r g} ) ( begin{aligned} text { fotal energy } &=2.90 times 6.3 mathrm{tatom} times 1.93 times 10^{-110 mathrm{rg}} &=5.60 times 10^{12} mathrm{mg} end{aligned} ) Total eneegy evolued. ( =2 cdot 63 times 10^{12} mathrm{erg}+5.60 times 10^{12} mathrm{eg} ) ( =8.2 times 10^{12} mathrm{erg} )