Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum Oct 2nd 2014, 10:13 AM #1 Junior Member   Join Date: Oct 2014 Posts: 2 Thermodynamics Get could anyone help me with an engineering problem- A quantity of oxygen is stored for the air tanks of the submarine and occupies a volume of 5meters cubed. The pressure of the gas is at atmospheric pressure, at an ambient temperature of 4degrees Celsius. What will be the pressure of the gas be if it is compressed to half it's volume and heated to a temperature of 42degrees Celsius. Calculate the mass of the oxygen using the density of oxygen and using the specific heat at constant volume ,calculate the characteristic gas constant and the specific heat capacity at constant pressure ,when Cv=660KJ/KgK. I'd appreciate any help on this question, I have no idea where to start on this question.   Oct 3rd 2014, 08:09 AM #2 Physics Team   Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,354 Use the Ideal gas law: PV=nRT. Here n (number of moles of gas) is constant, as is R, so: PV/T = nR = constant. Thus: P1V1/T1 = P2V2/T2 Where P1, V1, and T1 are the initial values of pressure, volume and temp (in kelvin) and P2, T2, and V2 are the final values. Solve for P2. For the second part, use PV=nRT to solve for n. You can use either initial values of P, V and T or final values - it doesn't matter, just don't mix them up. Then from n calculate total mass of gas. Post back with your answers, and if still having issues with it or the third part we'll help you along.   Oct 4th 2014, 06:11 AM #3 Junior Member   Join Date: Oct 2014 Posts: 2 Part 1 PV=nRT PV/T=nR P1V1/T1=P2V2/T2 P1- 101325 Pascal V1- 5m3 T1- 4oc -> 1092K P2- 463.9 V2- 5m3/ 2= 2.5m3 T2- 42oc -> 11 466K Using the equation i will solve the final pressure: 101325x 5/1092= 463.9 x 2.5/ 11 466 Final pressure= 463.9 Part 2 Use-PV=nRT I will be using the final values. Pressure= 463 Pascal 0.0045783370 Atmosphere Volume= 2.5m3 2500 L Temp= 11 466 K n = 0.01216 PV=nRT 463 x 2.5 = 0.01216 x 0.08206 x 11 466 1125.5 = 11.44 1125.5/ 11.44 = 0.1048080 (Mass of gas) Part 3 Specific gas constant- S= R/MW MW= R/S S= 0.08206/ 0.01216 = 6.74835 (Specific gas constant) Thanks for the reply, these are my workings out and i would appriciate any feedback and help you could offer.  Tags thermodynamics Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post ariana Thermodynamics and Fluid Mechanics 0 Oct 1st 2014 02:29 PM abcde Advanced Thermodynamics 2 Sep 12th 2014 02:43 PM KAJ0989 Advanced Thermodynamics 1 Dec 24th 2012 07:44 PM CNM DESIGN Thermodynamics and Fluid Mechanics 0 Aug 22nd 2010 04:35 PM AJEY Thermodynamics and Fluid Mechanics 1 Dec 15th 2009 10:12 PM