## Thermodynamics, first law, pressure increase, volume increase

1. The problem statement, all variables and given/known data
How much heat energy is needed to heat oxygen, mass=10g which is on temperature t=27°C to make the volume go up by 3 times while pressure is constant, and after that increase the pressure 2 times while volume is constant. Specific heat capacity of oxygen is cp= 908 J/KgK and cv=653 J/kgK.

2. Relevant equations
Q=m*cv(p)*delta(T)
Q=U+pV

3. The attempt at a solution

I tried and tried and triiied and i hate to come here to look for an answer its a probably an easy one, but i have a mental blockade, can't think of anything.

I have final result Q=11,32kJ if it helps(solution to this from my book)

I simply cannot find any relation or equation so that i can relate pressure and volume etc. I know general fomula Q=U+pV, but that didn't get me anywhere..

Thanks
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 pV/T = const const pressure: 1/(27+273) = 3 / (T + 273) --> dT = 600 Q1 = mc_v dT = 0.01kg * 908 * 600 = 5448 KJ const vol: 1 / (627 + 273) = 2 / (T + 273) --> dT = 900 Q2 = mc_pdT = 0.01kg * 653 * 900 = 5877 kJ Q_total = Q1 + Q2 = 11325kJ

 Quote by ppzmis pV/T = const const pressure: 1/(27+273) = 3 / (T + 273) --> dT = 600 Q1 = mc_v dT = 0.01kg * 908 * 600 = 5448 KJ const vol: 1 / (627 + 273) = 2 / (T + 273) --> dT = 900 Q2 = mc_pdT = 0.01kg * 653 * 900 = 5877 kJ Q_total = Q1 + Q2 = 11325kJ
See, I had absolutely no idea about pV/T part, that changes everything. THANK YOU VERY MUCH!!!!!!!!!!!!!!!!!!!!!!!!

I just had like 5 in a row "aha" moments :D Gas equation, fixed quantity of gas etc

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