0.600 L of Ar at 1.20atm and 227C is mixed with 0.200 L of O2 at 501 torr and 127 C in a 400ml flask at 27C. What is the pressure in the flask?

Answer 1

This was a confusing problem when first posted a few days ago and it's no less confusing to me now. However, I think what you must do is to use PV = nRT for the first gas and calculate n for Ar gas. Then use PV = nRT and calculate n for O2. Finally, add the moles and use PV = nRT again, this time using 27 C and 400 mL with the combined n.