Question

Find the energy required to excite 0.414 moles of h2 gas

Answer 1

Determination of number of moles of hydrogen gas,

N = PV/RT = 1 *1/0.082 *298 = 0.0409

The concerned reaction is H2 → 2H ; ∆H = 436 kJ mol-1

Energy required to bring 0.0409 moles of hydrogen gas to atomic state = 436 *0.0409 = 17.83 kJ

Calculate of total number of hydrogen atom in 0.0409 mole of H2 gas

1 mole of H2 gas has 6.02 * 1023 molecules

0.0409 mole of H2 gas = 6.02 *1023/1 * 0.0409 molecules

Since 1 molecule of H2 gas has 2 hydrogen atoms 6.02 * 1023 * 0.0409 molecules of H2gas

= 2 * 6.02 * 1023 * 0.0409 = 4.92 * 1022atoms of hydrogen since energy required to excite an electron from the ground state to the next excited state is given by

E = 13.6 eV = 13.6 * (1/1 – 1/4) = 13.6 * 3/4 = 10.2eV

= 1.632 * 10-21 kJ

Therefore energy required to excite 4.92 * 1022 electrons

= 1.632 * 10-21 * 4.92 * 1022 kJ = 8.03 * 10 = 80.3 kJ

Therefore total energy required = 17.83 + 80.3 = 98.17 kJ

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