Unfortunately you can't get density from two volumes, but I assume you meant 144g, mg, or kg, rather than mL. In that case Density = Mass/Volume = 144g, mg, or kg / 9 Liters.
144ml is just over 1/2 a cup.
The answer is 15,039 g hydrogen chloride (HCl).
Using Boyle's Law (P1V1=P2V2), we can set up the equation as (0.948)(150) = (0.987)(V2) to solve for V2. Solving for V2 gives us a volume of approximately 144 mL for the oxygen gas at a pressure of 0.987 ATM.