# Equilibrium Partial Pressure Kp/Kc Question

1. Dec 9, 2012

### YeyFunNOT

1. The problem statement, all variables and given/known data
At 100 o C Kc=.078 for the reaction SO2Cl2<-->SO2 + Cl2. In an equilibrium mixture the [SO2CL2]=.0108 M and [SO2]=.052 M.

What is the partial pressure of Cl2 in the eq. mixture?

2. Relevant equations
Kp=Kc(RT)$\Delta$n
P=RT/V

3. The attempt at a solution
I solve for Kp but I don't know how to find the partial pressure since neither the total pressure nor the volume is given.

2. Dec 10, 2012

### Staff: Mentor

Pressure can't be a function of the volume, which suggests in the end it will cancel out. Would it help to assume 1L total volume?

3. Dec 10, 2012

### YeyFunNOT

I tried that, here's the work:
P=RT=(.0821)(373)=30.6233 atm

Moles is M*L so all of the moles equal the concentration. Total number of moles is .0108+.052+.0162 (moles of Cl2)=.079 total moles. So the pCl2= .0162/.079*30.6233=6.27 atm.

The book says 5 atm so where am I going wrong?

4. Dec 10, 2012

### Staff: Mentor

List assumptions used to calculate this number.

But I don't see how the final answer can be 5 atm. Are you sure you have not missed a decimal point?

5. Dec 10, 2012

### YeyFunNOT

I used the ideal gas law, PV=nRT rearranged to solve for P. (I did this in another problem in the same set to get overall pressure). I just set the volume as 1 L.

I checked all the numbers and the answer in the book and everything seems correct. :S

6. Dec 10, 2012

### Staff: Mentor

P=nRT/V, what have you used for n?

7. Dec 10, 2012

### YeyFunNOT

Thanks for the help, I did indeed misplace a decimal xD.