Given the following data, what is the value of delta Gf (in kJ) for N2O4 (g) at 25C.

Question

N2O4(g)-----2NO2(g) Keq= 0.144
delta Gf: ? 51.30

I thought of using the equation:
delta G-RTlnQ

I am not sure if that's what I should use to find N2O4 though????

Choose one answer.

a. 46.40
b. -4.80
c. 102.60
d. 97.80
e. 107.40

Answer 1

I think this is what you want to do.
delta Gorxn = -RT*ln K
Solve for delta Gorxn. I get something like 4.8 kJ/mol but you need to confirm that.
Then DGorxn = (DGproducts)-(DGreactants)
4.8 = (2*NO2)-(N2O4)
4.8 = (2*51.3)-(N2O4)
(I look up the value of 51.3 for NO2.)
Solve for N2O4. I get something like 98 kJ/mol but check my work closely, especially for signs. I used 8.314 for R.