Chemistry Volume and Pressure

Question

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.

Answer 1

gas 1 = 5 L and 9 atm

gas 2 = 10 L and 6 atm

After the valve is opened, the final volume = 5 L + 10 L = 15 L

We can use Boyles law since the temperature is constant and only the volume (V) and pressure (P) change.

P1V1 = P2V2 ... Boyles law

For gas 1:

P1 = initial pressure = 9 atm

V1 = initial volume = 5 L

P2 = final pressure = ?

V2 = final volume = 15 L

Solving for P2 we have ... P2 = P1V1 / V2 = (9 atm)(5 L) / 15 L

P2 = 3 atm = partial pressure for gas 1

For gas 2:

P1 = initial pressure = 6 atm

V1 = initial volume = 10 L

P2 = final pressure = ?

V2 = final volume = 15 L

Solving for P2 we have ... P2 = P1V1 / V2 = (6 atm)(10 L) / 15 L

P2 = 4 atm = partial pressure for gas 2

Final Pressure in the tank = partial pressure gas 1 + partial pressure gas 2 = 3 atm + 4 atm

Final pressure in the tank = 7 atm