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DuckieDai Van der Waals Real-Gas Equation

Solve the van der Waals equation for pressure or temperature, compare with the ideal gas law, or rearrange for a or b.

Version 1.0.0 · Not calculator tested

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chemistry · MIT License

Overview

Solve the van der Waals equation for pressure or temperature, compare with the ideal gas law, or rearrange for a or b.

Usage

Inputs

  • Pressure in atm, volume in L, amount in mol, and temperature in K as required
  • a in L^2*atm/mol^2 and b in L/mol

Outputs

  • Requested pressure, temperature, a, or b
  • Ideal/real pressure comparison and percent change

Units: Use atm, L, mol, K, L^2*atm/mol^2, and L/mol consistently with R = 0.082057 L*atm/(mol*K).

Assumptions and limitations

Assumptions

  • A single van der Waals parameter pair represents the gas in a single modeled phase.
  • The equation is an educational real-gas approximation, not a high-accuracy equation of state.

Constraints

  • n, V, and T are positive; supplied a and b are nonnegative; free volume V-n*b must be positive.

Known failures

  • Solved negative a or b, or calculated nonpositive pressure, indicates inconsistent data or an unsuitable modeled state.
  • Near phase boundaries or the critical region, the equation may give multiple or inaccurate states.

Compatibility and review

Review status
Not calculator tested
Tested on
The owner reports personally testing the supplied archive programs on a calculator; exact model, OS, and Python App versions were not recorded
What happened
Owner reported interactive testing is disclosed, but the published bytes are not labeled independently calculator tested because the environment is unrecorded and Arrhenius received a narrow intake correction
Dependencies
No imports
Suggested calculator name
VDW — you can give it another valid, unique name when you transfer it
Desktop test cases
Not available for this interactive-only source

This exact source auto-launches an interactive calculator session, so compatibility evidence comes from the recorded physical-device review rather than an importable desktop fixture.

Browser preview

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Simulation boundary: This preview uses a reviewed browser adapter. It does not execute the downloaded Python and does not prove TI-Python or calculator compatibility.

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Exact reviewed bytes

Source code

Download .py

View source below, copy it when JavaScript is available, or download the exact .py bytes.

  1. R=.082057
  2. def intro(n):
  3. print("+----------------------+");print("| "+n+" |");print("| ___(o )> quack! |");print("| by DuckieDai |");print("+----------------------+");input("ENTER to start: ")
  4. def num(s):
  5. while 1:
  6. try:return float(input(s))
  7. except:print("Enter a number")
  8. def pos(s):
  9. while 1:
  10. x=num(s)
  11. if x>0:return x
  12. print("Must be positive")
  13. def nonneg(s):
  14. while 1:
  15. x=num(s)
  16. if x>=0:return x
  17. print("Must be 0 or more")
  18. def pick(s,m):
  19. while 1:
  20. try:
  21. x=int(input(s))
  22. if x>0 and x<=m:return x
  23. except:pass
  24. print("Invalid choice")
  25. intro("VAN DER WAALS")
  26. print("1 Pressure 2 Temp");print("3 Real vs ideal 4 Find a/b")
  27. c=pick("Choose 1-4: ",4)
  28. if c==1 or c==3:
  29. n=pos("Moles n: ");v=pos("Volume L: ");t=pos("Temp K: ");a=nonneg("a: ");b=nonneg("b: ")
  30. if v<=n*b:print("Need V > n*b")
  31. elif c==1:print("P atm =",n*R*t/(v-n*b)-a*n**2/v**2)
  32. else:
  33. pi=n*R*t/v;pr=n*R*t/(v-n*b)-a*n**2/v**2;print("Ideal P =",pi);print("Real P =",pr);print("% change =",100*(pr-pi)/pi)
  34. elif c==2:
  35. p=pos("P atm: ");n=pos("Moles n: ");v=pos("Volume L: ");a=nonneg("a: ");b=nonneg("b: ")
  36. if v<=n*b:print("Need V > n*b")
  37. else:print("T K =",(p+a*n**2/v**2)*(v-n*b)/(n*R))
  38. else:
  39. q=pick("1 find a 2 find b: ",2);p=pos("P atm: ");n=pos("Moles n: ");v=pos("Volume L: ");t=pos("Temp K: ")
  40. if q==1:
  41. b=nonneg("b: ")
  42. if v<=n*b:print("Need V > n*b")
  43. else:print("a =",v**2/n**2*(n*R*t/(v-n*b)-p))
  44. else:
  45. a=nonneg("a: ");print("b =",(v-n*R*t/(p+a*n**2/v**2))/n)
  46. input("ENTER for guide: ");print("a=attractions, b=molecule volume");print("V must exceed n*b");print("DuckieDai: done!");input("ENTER to exit: ")
Filename
vdW.py
Size
1624 bytes
SHA-256
eb7eb29ffccdc9186af4f15e996ee6010a55a168c090ff52158359ac61afa476

Transfer and launch

  1. Confirm that your calculator is the Python-capable model named above. This release has no verified calculator OS or Python App version; treat transfer and execution as unverified until independently tested.
  2. Download the .py source above and verify its SHA-256 digest if your computer provides that option.
  3. Use TI Connect CE to send the Python file to a compatible calculator. VDW is a suggested name; you may choose another valid, unique calculator name.
  4. Open the Python App, select the program, and check sample inputs before relying on other results.

Read the complete installation, launch, troubleshooting, and removal guide.

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Version history

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