Physical Chemistry Assignment
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Added on 2020-04-15
Physical Chemistry Assignment
Added on 2020-04-15
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SOLUTIONS 1. A transition of particular importance in O2 gives rise to the ‘Schumann– Runge band’ in the ultraviolet region. The wavenumbers ( in cm-1) of transitions from the ground state to the vibrational levels of the first excited state ( 3Su-) are50,062.6 50,725.451,369.0 51,988.6 52,579.0 53,143.4 53,679.6 54,177.0 54,641.8 55,078.2 55,460.0 55,803.1 56,107.3 56,360.3 56,570.6 (a)What is the dissociation energy of the upper electronic state as determined by constructing a Birge– Sponer plot? Ans: In this case, we need to obtain the independent variable (x-variables) against the given dependent variable (wave numbers) and this is done as follows but first we arrange the values: vG(v)1450,062.61350,725.41251,369.01151,988.61052,579.0953,143.4853,679.6754,177.0654,641.8555,078.2
455,460.0355,803.1256,107.3156,360.3056,570.61234567891011121314150100002000030000400005000060000vG(v)Figure 1: The Birge-Sponor plotThe dissociation energy is the sum of energy levels from v=0 to v= 15Hence De= 807745.9Jmol-1(b)The same excited state is known to dissociate into one ground state O atom and one excited state atom with an energy 190 kJ mol-1 above the ground state. (This excited atom is responsible for a great deal of photochemical reactivity in the atmosphere.) Ground state O2 dissociates into two ground- state atoms. Use this information to calculate the dissociation energy of ground- state O2 from theSchumann– Runge data.
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