Answer is: volume will be 6,7 L. Boyle's Law: the pressure volume law - volume of a given amount of gas held varies inversely with the applied pressure when the temperature and mass are constant. p₁V₁ = p₂V₂. 90 kPa · 5 L = 67 kPa · V₂. V₂ = 90 kPa · 5 L / 67 kPa. V₂ = 6,7 L, but same amount of oxygen.