**Question**

When 5.0 moles of O_{2} are confined to a 24 liter container at 87 °C, the pressure is 6.0 atm. If the oxygen is allowed to isothermally expand to 36 liters, what is the new pressure?

**Solution**

Isothermal means constant temperature therefore, the gas law needed is Boyle's Law where

P_{i}C = P_{f}V_{f} where

P_{i} = initial pressure

V_{i} = initial volume

P_{f} = final pressure

V_{f} = final volume

Solve Boyle's Law for P_{f}

P_{f} = ( P_{i}V_{i} ) / V_{f}

P_{f} = ( 6.0 atm x 24.0 L ) / 36.0 L

P_{f} = 144.0 atm L / 36.0 L

P_{f} = 4.0 atm

**Answer**

The new pressure of O_{2} is 4.0 atm.