The volume of Oxygen : 20,000 L
Given
400 L : initial volume
150 atm  : initial pressure
3 atm : final pressure
Required
Final volume
Solution
Boyle's Law Â
At a fixed temperature, the gas volume is inversely proportional to the pressure applied Â
[tex]\rm p_1V_1=p_2.V_2\\\\\dfrac{p_1}{p_2}=\dfrac{V_2}{V_1}[/tex]
Input the value :
Vâ = (PâVâ)/Pâ
Vâ = 150 atm x 400 L / 3 atm
Vâ = 20,000 L