Part A For the reaction of oxygen and nitrogen to form nitric oxide, consider th

Question

Part A

For the reaction of oxygen and nitrogen to form nitric oxide, consider the following thermodynamic data:

Calculate the temperature above which this reaction is spontaneous.

Express your answer numerically in kelvins.

The standard free energy change ?G? and the equilibrium constant K for a reaction can be related by the following equation:

?G?=?RTlnK

where T is the Kelvin temperature and R is equal to 8.314J/(mol?K).

Part B

Calculate the equilibrium constant for the reaction forming nitric oxide at room temperature, 25 ?C.

Express your answer numerically.

Explanation / Answer

At some temperature, the reaction will have a free energy change (DG) of zero. Calculate that temperature first:

DG = DH - TDS
0 = 180.5 kJ/mol - T(24.8 J/molK)

Change kJ to mol and solve for T:
-1.805 X 10^5 J/mol = -T(24.8 J/molK)
T = 7278 K

So at any temperature below 7278 K, this reaction is not spontaneous, but at any temperature above this, the reaction is spontaneous.

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