DuckieDai Henderson-Hasselbalch Equation Python Program

chemistry · MIT License

Overview

Solve pH = pKa + log10([A-]/[HA]) and its pKa, ratio, conjugate-base, and weak-acid rearrangements.

Not calculator tested
Downloaded 34 times
Version 1.0.0
1396 bytes
Uses math

Download hhEQ.py Read the source How to install

Before you run it

TI-84 Plus CE Python · No calculator OS or Python App version has been verified.
TI Connect CE .py transfer is the intended path; calculator OS, Python App, transfer, and execution have not yet been tested for this release
The solution behaves as a weak-acid/conjugate-base buffer and concentration ratio approximates the activity ratio.
Temperature and ionic-strength effects are outside the calculation.
Both buffer component concentrations must be positive where used as logarithm arguments or divisors.

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Follow the same opening, solve menu, prompts, validation, and result flow as the downloadable program.

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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.

Learn the math

How the Henderson-Hasselbalch equation works

The idea

A buffer is a mixture of a weak acid and its conjugate base. Its pH depends on the acid's pKa and on the ratio of base to acid, not on how much of each there is in total.

When the two concentrations are equal, the pH equals the pKa.

The formula

pH = pKa + log10([A-]/[HA])

pH: acidity of the buffer
pKa: -log10 of the acid's Ka
[A-]: concentration of the conjugate base
[HA]: concentration of the weak acid

Using the program

1 finds pH. 2 finds pKa. 3 finds the ratio of base to acid. 4 finds either concentration when you know the other.
The program also tells you which form dominates.

Worked example

An acetate buffer has pKa = 4.76, 0.2 M acetate, and 0.1 M acetic acid. Choose 1 and enter 4.76, 0.2, and 0.1.

pH = 4.76 + log10(0.2/0.1)

The program shows pH = 5.06 (it prints more decimal places) and Base form dominates.

Tips and common mistakes

Base goes on top of the ratio. Swapping them flips the sign of the log term.
The equation works best when the ratio is between about 0.1 and 10.
Use concentrations or moles for both, as long as they share one volume.

Where this comes up

It is the main tool of the buffers unit in general chemistry and is used throughout biochemistry and physiology, where blood and cell buffers are described by exactly this ratio.

Exact reviewed bytes

Source code

Download .py

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

from math import log
def intro(n):
 t=n[:16];l=(16-len(t))//2;r=16-len(t)-l
 print("+----------------------+");print("|   "+" "*l+t+" "*r+"   |");print("|       __             |");print("|   ___(o )>  quack!   |");print("|   \\ <_. )           |");print("|    `---'             |");print("|     by DuckieDai     |");print("+----------------------+");input("ENTER to start: ")
def num(s):
 while 1:
  try:return float(input(s))
  except:print("Enter a number")
def pos(s):
 while 1:
  x=num(s)
  if x>0:return x
  print("Must be positive")
def pick(s,m):
 while 1:
  try:
   x=int(input(s))
   if x>0 and x<=m:return x
  except:pass
  print("Invalid choice")
intro("BUFFER PH")
print("HENDERSON-HASSELBALCH");print("1 pH  2 pKa");print("3 A-/HA  4 find A or HA")
c=pick("Choose 1-4: ",4)
if c==1:
 p=num("pKa: ");r=pos("[A-]: ")/pos("[HA]: ");print("pH =",p+log(r,10))
elif c==2:
 p=num("pH: ");r=pos("[A-]: ")/pos("[HA]: ");pk=p-log(r,10);print("pKa =",pk);print("Ka =",10**(-pk))
elif c==3:
 r=10**(num("pH: ")-num("pKa: "));print("A-/HA =",r)
else:
 r=10**(num("pH: ")-num("pKa: "));q=pick("1 A- 2 HA: ",2)
 if q==1:print("[A-] =",pos("[HA]: ")*r)
 else:print("[HA] =",pos("[A-]: ")/r)
if r==1:print("pH=pKa")
elif r>1:print("Base form dominates")
else:print("Acid form dominates")
input("ENTER for guide: ");print("Best buffer: pH near pKa");print("DuckieDai: done!");input("ENTER to exit: ")

from math import log
def intro(n):
t=n[:16];l=(16-len(t))//2;r=16-len(t)-l
print("+----------------------+");print("| "+" "*l+t+" "*r+" |");print("| __ |");print("| ___(o )> quack! |");print("| \\ <_. ) |");print("| `---' |");print("| by DuckieDai |");print("+----------------------+");input("ENTER to start: ")
def num(s):
while 1:
try:return float(input(s))
except:print("Enter a number")
def pos(s):
while 1:
x=num(s)
if x>0:return x
print("Must be positive")
def pick(s,m):
while 1:
try:
x=int(input(s))
if x>0 and x<=m:return x
except:pass
print("Invalid choice")
intro("BUFFER PH")
print("HENDERSON-HASSELBALCH");print("1 pH 2 pKa");print("3 A-/HA 4 find A or HA")
c=pick("Choose 1-4: ",4)
if c==1:
p=num("pKa: ");r=pos("[A-]: ")/pos("[HA]: ");print("pH =",p+log(r,10))
elif c==2:
p=num("pH: ");r=pos("[A-]: ")/pos("[HA]: ");pk=p-log(r,10);print("pKa =",pk);print("Ka =",10**(-pk))
elif c==3:
r=10**(num("pH: ")-num("pKa: "));print("A-/HA =",r)
else:
r=10**(num("pH: ")-num("pKa: "));q=pick("1 A- 2 HA: ",2)
if q==1:print("[A-] =",pos("[HA]: ")*r)
else:print("[HA] =",pos("[A-]: ")/r)
if r==1:print("pH=pKa")
elif r>1:print("Base form dominates")
else:print("Acid form dominates")
input("ENTER for guide: ");print("Best buffer: pH near pKa");print("DuckieDai: done!");input("ENTER to exit: ")

Filename: hhEQ.py
Size: 1396 bytes
SHA-256: 9ce6e66ef66245a6c12613b38a6f4bebb684e0f42bc77045715c7d58500b41ad

Usage

Inputs

pH and pKa as required
Positive conjugate-base and weak-acid concentrations in matching units

Outputs

Requested pH, pKa, concentration ratio, or component concentration

Units: pH, pKa, and [A-]/[HA] are dimensionless; component concentrations must use the same unit.

Assumptions and limitations

Assumptions

The solution behaves as a weak-acid/conjugate-base buffer and concentration ratio approximates the activity ratio.
Temperature and ionic-strength effects are outside the calculation.

Constraints

Both buffer component concentrations must be positive where used as logarithm arguments or divisors.

Known failures

The equation is unreliable when a buffer component is exhausted or the solution is too concentrated/nonideal.
Extreme pH-pKa differences can overflow or underflow the displayed ratio.

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: math
Suggested calculator name: HHEQ — 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.

Transfer and launch

Download the .py file, send it to your calculator with TI Connect CE as HHEQ or another name, then open the Python App and try the worked example on this page first. This release has no verified calculator OS or Python App version; treat transfer and execution as unverified until independently tested.

Full installation and troubleshooting guide. Check your teacher's or exam's rules before using any program.

Version history

1.0.0 — current version, published 2026-09-23. Download this reviewed version

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