Ok i am revising for a failed exam i have to resit. I need the formulas and methods to these questions below.?

Question

Ok i am revising for a failed exam i have to resit. I need the formulas and methods to these questions below. I will give you all the answers.


Oxygen trapped inside an insulated smooth piston-cylinder apparatus has a volume of 0.3m^3, pressure of 2.5bar and tempreture of 20 degree C. It is then subjected to the following thermodynamic processes sequentially:

Process 1: heating under constantvolume condition until its tempreture increases to 120 degree C

Process 2: Undergo polytropic expansion where PV^1.4 = constant, until its volume increases to 0.5m^3

Process 3: Cooling under constant pressure condition until its volume decreases to 0.4m^3

Assuming:

Universal gas constant = 8.314kJ/kmol.K, and
Molar mass of oxygen molecule = 32kg/kmol

Determine

(i) the characteristic gas constant of oxygen in kj/kgK.

Answer:0.26 kJ/ kg K

ok is the formula:
Rspecific=R/M

Specific=Oxygen
R=Universal gas constant
M=molar mass

so...

Roxygen= 8.314/32 = 0.26 kJ/kg K ??

Could someone help me with the rest, explaning them in the simple format above. giving me the formulas and methods... Thanks :)

(ii)the mass of oxygen in the piston-cylinder apperatus

Answer:0.985 kg

ok is the formula:
PV=mRT

P=pressure/2.5
V=volume/0.3
R=Universal gas constant/0.26
T=Tempreture/20
m=mass ?

But i don't get the correct answer! :(

(iii) the pressure of oxygen after process 1

Answer:3.35 bar

(iv) the pressure of oxygen after process 2

Answer:1.64 bar

(v) the tempreture of oxygen after process 3

Answer:256.2 K

Answer 1

Study: that's what exams are for.



If you can't do these problems, then you fail the course. This too difficult to understand?

Answer 2

When using PV=nRT I believe Pressure must be in pascals. However you can just use PV/T = a constant.



For two, 1 suggest you work out what the constant is.



Since pv^1.4 = a constant and you are given v then you can work out P at the new V

The use PV=NRT



If you have PV and T at the end of stage 2 then you can surely work out the value at the end of stage 3 as P remains the same and you know V(final)

Answer 3

PV = nRT where n is not the mass but the molar measure of the gas inside the piston. Look at the dimensions.

Answer 4

The stupid and humorous question my little ones come out with. they are being completely intense whilst they ask and each each now and then I purely cant help myself and wreck right into a grin approximately their inocence.