# Thread: First law of thermodynamics! Simple yet complex question

1. ## First law of thermodynamics! Simple yet complex question

Hi all I am really struggling with my worked example at my placement. Please help! My answers are awfully wrong.

A pump compressing hydrogen from a low pressure to a high pressure tank where the tanks pressure is constant and H2 is an ideal gas.
Hydrogen: (H2: MW = 2, Cv = 10 kJ/kgK)
Low pressure tank: (P = 4 bar, T = 30oC)
High pressure tank: (P = 100 bar).

1) Apply the first law of thermodynamics eliminating terms not needed
2) Find the compressor outlet temp when the compression goes along an adiabatic and polytrophic process

2. dQ=CvdT+PdV energy equation statement of 1st Law
PdV+VdP=nRdT-= gas law
Next prove
Cp=Cv+nR

Now from these you should be able to get
PV^k= constant when dQ=0
k=Cp/Cv

I gave you more than I should have to get you started
Now you do the rest of your homework..

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