Solving Thermodynamics Ideal Gas Probs: Q, W, ΔU w/Help | Physicsforums.com

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SUMMARY

This discussion focuses on solving thermodynamic problems involving ideal gases, specifically calculating heat (Q), work (W), and change in internal energy (ΔU) across various processes. The user seeks guidance on applying key equations such as ΔU = Won + Q, ΔU = (3/2)nRΔT, and the ideal gas law PV = nRT. The conversation emphasizes the importance of understanding the relationships between these variables and the application of specific equations for different thermodynamic processes, including isothermal expansions.

PREREQUISITES
  • Understanding of the ideal gas law (PV = nRT)
  • Familiarity with the first law of thermodynamics (ΔU = Q - W)
  • Knowledge of work done by gases during expansion (W = -∫PdV)
  • Basic concepts of thermodynamic processes (isothermal, adiabatic, etc.)
NEXT STEPS
  • Study the derivation and application of the ideal gas law in various scenarios
  • Learn how to calculate work done during isothermal and adiabatic processes
  • Explore the implications of the first law of thermodynamics in closed systems
  • Investigate the relationships between Q, W, and ΔU in different thermodynamic cycles
USEFUL FOR

Students and professionals in physics, engineering, and chemistry who are working on thermodynamics, particularly those needing to solve ideal gas problems and understand the principles of energy transfer in gas systems.

skoopfadj
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I'm sorry I cannot conform to the default format Physicsforums.com; it is because I do not even know the first step to solving these sorts of problems, I don't know which equations to use which is a major problem. Here are the types of questions I require understanding.
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An ideal gas goes through three processes (A>B>C>[A]) (Triangular form) (PV Chart)
How would I figure out The Q, W, and ΔU (internal energy) for A to B, B to C, C to A?
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On another graph using variables but this time with numerical values for P and V on the axis, how would I find the work done by a monatomic ideal gas as it expands from point A to point C along the path shown in the figure? Also, how much heat would be absorbed BY the gas during this process?
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Finding the net work, heat, and ΔU in another PV Graph with data on the axis-es?
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Calculating temperature, work, and/or internal energy in another PV Graph?
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Whether or not W, Q, or ΔU is positive(gained) or negative(released) in an ideal gas system as well as how those three (Q,W,..U) are related?
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I really wish to work on the problems myself, so I have only asked what procedures I should take.
Here is a list of equations I have scavenged.

ΔU = Won + Q

ΔU = (3/2)nRΔT

Won = -PΔV

P1V1 = P2V2

(P1V1)/T2 = (P2V2)/T2

PV = nRT

Is there any important equation that I am missing?
 
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I think that since you are working with idel gasses, you can dervie most of the stuff from 3-4 equations, namely:
The ideal gas law : pV = nRT
The Laws of thermodynamics.(2-3 laws is useful).

If you want to find the Work done during a isothermal(T constant) step e.g.:
W = -\int\limits_{V_1}^{V_2}\! p\,\text{d}V = -\int\limits_{V_1}^{V_2}\! \dfrac{nRT}{V}\,\text{d}V = -nRT\left(\ln(V_2)-\ln(V_1)\right) = -nRT\ln\left(\dfrac{V_2}{V_1}\right)
I hope that I understood your question.
 

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