A 69.4 L cylinder containing C2H6 at a pressure of 570 torr is connected by a valve to 105 L cylinder containing C6H6 at 0.350 atm pressure. Calculate the partial pressure (atm) of C6H6 when the valve is opened.

The question is about partial pressure of C6H6 and Dalton's Law tells us that gases act independently in mixtures; therefore, just ignore the C2H6 (but not the container). Then, for C6H6,

P1V1 = P2V2
You know P1 and V2 for C6H6. P2 is what you are looking for and V2 is just the sum of the two volumes of the containers.