Posted by kat on .
A 265 mL flask contains pure helium at a pressure of 747 torr. A second flask with a volume of 485 mL contains pure argon at a pressure of 721 torr .If the two flasks are connected through a stopcock and the stopcock is opened, what is the partial pressure of helium?

chemistry 
DrBob222,
Use PV = nRT for the He flask to determine the number of moles He. Then use PV = nRT for the two flasks connected (add volumes to obtain total volume) and solve for P. Remember pressure must be in atmospheres. There is no T given; therefore, make up a convenient number. I suggest 273 K.