[Joules23]

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#1) Consider the following reaction at 298 K.
2 SO2(g) + O2(g) -->  2 SO3(g)

An equilibrium mixture contains O2(g) and SO3(g) at partial pressures of 0.31 atm and 2.9 atm, respectively. Using data from Appendix 4, determine the equilibrium partial pressure of SO2 in the mixture.
  atm

My attempt:
First calculat DG, which = -142KJ
Then use: DG = -RTlnK, to find K
-142 = (-8.314E-3)(298)(lnK)
K=7.78

7.78= (2.9^2/(.31X^2))
X= SO2 = 1.87atm
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[Yggdrasil]

For figuring out the equilibrium partial pressure, you need to make an ICE table.  At equilibrium you will not have 2.9atm of SO₃ because some will react to form more O₂ and SO₂.

[Joules23]

but in the problem it says "An equilibrium mixture contains O2(g) and SO3(g) at partial pressures ..."
So i thought that meant it is already at equilibrium..

[Yggdrasil]

Ah, you are correct.  When I calculate K I get 7.78x10²⁴.  Maybe that is your problem.

[Joules23]

i dunno how i missed that lol, thanks!

[champ]

check your units.. convert "Kj" to "J" and then u will find the right ans. for "k". lol

[Joules23]

No, my units are fine, the KiloJoules (or joules) cancel out, K has no units.. its just i guess when i glanced at my calulator i missed the E24 part