Question

If 200 cm3 of H2 gas contained in a cylinder under a pressure of 1200 mmHg are forced into a cylinder whose volume is 400 cm3 and which already contains CH4 gas under a pressure of 800 mmHg, what will be the total pressure (in mmHg) in the cylinder at the same temperature?

My answer is 1200+ 800 = 2000mmHg but that seems to easy because they have given me all these other units

Answer 1

I don't think so. The pressure of H2 in the first cylinder is 1200 initially and its volume is 200 cc. When it goes into the 400 cc cylinder the pressure will drop to 600 mm Hg. (P1V1 = P2V2). That will make Ptotal jn the 400 cc container = 600 + 800 = ?