Untitled - Kelly Walsh High School

Entropy and Free Energy 261
Before we can use this equation, we need to write the expression for Q:
[NO2 ]
Q
In addition to writing the Q expression, we also need to determine the value of
G before using the equation. We can find G using the following relationship
and values.
∆G ∆Gproducts ∆Greactants 2
[NO] 2 [O2 ]
NO(g) 86.71 kJ/mol
O2(g) 0 kJ/mol (exactly)
NO2(g) 51.84 kJ/mol
Entering the Gibbs free energy values into the relationship gives:
∆G [(2 mol NO2)(51.84 kJ/mol)] [(2 mol NO)(86.71 kJ/mol)
(1 mol O2)(0.000 kJ/mol)]
∆G 69.74 kJ
Returning to our key relationship for this problem:
∆G ∆G RT ln Q
[NO2 ]
∆G ∆G RT ln
2
[NO] 2 [O2 ]
We can now enter the values into the appropriate places. We also need a kJ/J
conversion.
[1.00]
∆G 69.74 kJ (8.314 J/molK)(298 K) ln
2
[2.00] 2 a
[0.500]
1kJ
103 J b
[1.00] 2
∆G 69.74 kJ (2.477572 kJ) ln
[2.00]
∆G 69.74 kJ (2.477572 kJ) ln 0.500
∆G 69.74 kJ (2.477572 kJ) (0.693147)
∆G 71.45732 71.46 kJ
2 [0.500]
The first law of thermodynamics states that the total energy of the universe is
constant. The second law of thermodynamics states, that in all spontaneous
processes, the entropy of the system increases. Entropy is a measure of the dispersion
of energy from a localized one to a more disperse one. It can be