Physical Chemistry: Chemical Equlibrium

[jamesrb]

Homework Statement

For the reaction:
2SO_3(g) →2SO_2(g)+O_2(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?

Homework Equations

Δ_rxnG°=-RTlnK

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.

 

[Borek]

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?

 

[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

 

[Borek]

Simple check:

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

 

[jamesrb]

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

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

 

[Chestermiller]

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

What equation did you use to get the molar amounts?

Chet

 

[Borek]

What equation did you use

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