# Physical Chemistry: Chemical Equlibrium

1. Oct 26, 2014

### jamesrb

1. The problem statement, all variables and given/known data
For the reaction:
2SO3(g) →2SO2(g)+O2(g)
when 2.00 mol of SO3 is added to a flask at 10.0 L and 350 K at fixed volume, at equilibrium the ratio of SO2:SO3 is 0.663. What is the values of the equilibrium constant? What is ΔG° at this temperature?
2. Relevant equations
ΔrxnG°=-RTlnK

3. The attempt at a solution
I cannot figure out how to find K. I'm thinking I need to find the partial pressures of the various gases in order to get it but I cannot see how to do that.

2. Oct 26, 2014

### Staff: Mentor

How many moles of SO2 and SO3 together? Knowing how many moles in total and the ratio, can you calculate number of moles of each?

3. Oct 26, 2014

### jamesrb

Well if we used 2.00 moles of SO2 to start then:
1.326 moles of SO2
0.674 moles of SO3
at equilibrium

4. Oct 26, 2014

### Staff: Mentor

Simple check:

$$\frac {1.326}{0.674} \neq 0.663$$

5. Oct 26, 2014

### jamesrb

I though I could but nothing I can come up with gives me a ratio of 0.663

6. Oct 26, 2014

### Staff: Mentor

What equation did you use to get the molar amounts?

Chet

7. Oct 27, 2014

### Staff: Mentor

I would ask "what equations" (and that's an important hint).