Thethermodynamic properties for a reaction are related by the equationthat defin

Question

Thethermodynamic properties for a reaction are related by the equationthat defines the standard free energy, Change in G, in kJ/mol:

Change in G = change in H – T change in S

where change inH is the standard enthalpy change in kJ/mol and change in S orentropy is the standard entropy change in J/mol * K. A goodapproximation of the free energy change at other temperatures

Change in freeenergy or G, can also utilize this equation by assuming enthalpy(Change in H) and entropy (Change in S) change little withtemperature.

For the reactionof oxygen and nitrogen to form nitric oxide, consider the followingthermodynamic data:

Change in H reaction

180.5 kj/mol

Change in S reaction

24.8 J/mol * K

Calculate thetemperature above which this reaction is spontaneous.Express in kelvins. T=    ? K

Change in H reaction

180.5 kj/mol

Change in S reaction

24.8 J/mol * K

Explanation / Answer

We Know that :      According to Gibb's energy :         G = H - TS       The given Reaction is :          N2 + O2 --------> 2NO          Forequilibrium the change in free energy is zero.       H = T S         T = 180.5 x 103 J / mol /   24.8 J /mol-K              = 7278.2258 K         If the temperatureis greater than 7278.2258 Kthe above Reaction becomes spontaneous.         If the temperatureis greater than 7278.2258 Kthe above Reaction becomes spontaneous.

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