[DarthPipsqueak]

I'm having a bit of trouble solving this problem:

A mixture of CS2 (g) and excess O2 (g) is placed in a 10.0 L reaction vessel at 100.0 degrees Celsius and a pressure of 3.00 atm. A spark causes the CS2 to ignite, burning it completely according to the equation:

CS2 (g) + 3O2 (g) ---> CO2 (g) + 2SO2 (g)

After reaction, the temperature returns to 100.0 degrees Celsius, and the mixture of product gases (CO2, SO2, and unreacted O2) is found to have a pressure of 2.40 atm. What is the partial pressure of each gas in the product mixture?

[Borek]

How many moles before, how many moles after? Does the difference in number of moles tell something about the initial amount of CS₂?