The valve between a 5-L tank containing a gas at 9 atm and a 10-L tank containing a gas at 6 atm is opened.Calculate the final pressure in the tanks.
A)3 atm
B)4 atm
C)7 atm
D)15 atm
E)none of these

Question

Quizplus · Accepted Answer

The initial total volume of gas is 15 L and the initial total pressure is (5L*9atm + 10L*6atm) / 15L = 7 atm (using the formula P1V1 = P2V2). When the valve is opened, the gases will mix and reach a common final pressure. Using the equation (P1V1 + P2V2) / (V1 + V2) = Pf, we can solve for Pf: 
Pf = (5L*9atm + 10L*6atm) / (5L+10L) = 7 atm
Therefore, the final pressure in the tanks is 7 atm, which is answer choice C.

The Valve Between a 5-L Tank Containing a Gas at 9