Thermodynamics first law closed system

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Discussion Overview

The discussion revolves around calculating work done during various heating and expansion cycles of gases in closed systems, specifically focusing on helium, methane, and carbon dioxide. The context includes theoretical and practical applications of the first law of thermodynamics in rigid and expanding gas scenarios.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant presents a scenario involving a rigid walled tank containing helium and seeks to determine the work done during a heating cycle from 10 °C to 50 °C.
  • Another participant inquires about the method to calculate work done, suggesting the use of the integral of pressure times volume change (W=∫p dV) and asks for advice on applicable expressions.
  • A different scenario is introduced involving a gas storage vessel with methane, where the work done by the gas on its surroundings during heating from 20 °C to 35 °C is questioned.
  • Further, a participant describes an example with one mole of CO2 in a piston, expanding isothermally to four times its volume, and seeks to calculate the work done on the surroundings, noting the ideal gas behavior.
  • Another complex example is presented involving CO2 charged at 2 bar, expanding isothermally to twice its volume, with additional considerations for work done against a spring force during the expansion.
  • Participants express a need for formulas to determine the work done by the system and against the spring in the context of the described scenarios.

Areas of Agreement / Disagreement

The discussion remains unresolved with multiple competing views on how to calculate work done in different scenarios. Participants have not reached consensus on specific formulas or methods applicable to the various cases presented.

Contextual Notes

Limitations include the need for specific assumptions regarding gas behavior, the dependence on definitions of work in thermodynamic contexts, and unresolved mathematical steps in the calculations presented.

jordan2delta
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1) A rigid walled tank 5m3 contains helium at 10 bar. The cylinder is heated from 10 °C to 50 ° C. What is the work done during the heating cycle.
 
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how can determinate the work done during the heating cycle?
W=integral of pDV

which expression can I use to get the work done during the heating cycle?any advice?


1) A rigid walled tank 5m3 contains helium at 10 bar. The cylinder is heated from 10 °C to 50 ° C. What is the work done during the heating cycle.
 
2) An expanding gas storage vessel contains 5 m3 of methane at 1.1 bar. On a hot day the gas is heated from 20 °C to 35 °C. What work is done by the gas on its surroundings

expression to calculate the work by the gas on the surroundings?
knowing that V=5m^3
p=1.1bar
t1=20 degree Celsius
t2= 35 degree Celsius
t2=
 
3)One mole of CO2 is charged to a piston at 10 bar pressure 293K. The piston is allowed to expand to 4 times its volume isothermally. What work is done on the surroundings? The gas behaves ideally

A more complicated example using a polyatomic gas
Part1
– CO2 is charged at 2 bar to a piston at 298 K volume 0.5 m3. It is known to vary as polytonic gas PV2=C. The gas is allowed to expand isothermally to twice its volume what work is done by the system

Part 2
– A Spring force (5 kN/m extension) is added to retain the piston what work is done this time if the expansion is the same and how much work is done against the spring the piston area is 0.1 m2

please help me! I really need formulas to determinate work done by the system, and the work against the spring
 

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