Run a titration, watch the curve, find the endpoint
Pick an analyte and a titrant, add drops from the burette, and compare your curve with the exact charge-balance calculation.
- Set upanalyte, concentration, titrant, indicator.
- Titrateadd drops (or drag the stopcock) and watch the flask and curve.
- Find the endpointthe derivative plots reveal the equivalence point.
- Go furtherbuild a buffer, or take the unknown-sample challenge.
1 · Setup
2 · Bench
Tip: near the endpoint, switch to single drops — the pH jumps fast.
3 · Readouts
- Titrant added
- 0.00 mL
- Moles titrant
- 0.000000 mol
- pH (exact)
- –
- Equivalence vol.
- –
- Half-equivalence
- –
- Endpoint (2nd deriv.)
- –
Titration curve
Add drops to grow the curve point by point. The dashed line is the exact equilibrium calculation.
First derivative
dpH / dVSecond derivative
d²pH / dV²Buffer recipe
Adding strong base converts acid into conjugate base; strong acid does the reverse — watch the pH move (or not).
Result
- pH (exact solver)
- –
- pH (Henderson–Hasselbalch)
- –
- Δ (exact − H–H)
- –
- pKa of the pair
- –
- Buffer capacity β
- –
- Final volume
- – mL
- Effective range (pKa ± 1)
- –
- ΔpH · 1 mL of 1 M NaOH
- –
- same addition to pure water
- –
Buffer capacity
β = dB/dpH (mol·L⁻¹·pH⁻¹)The peak sits at pH = pKa: the buffer is strongest when [acid] = [base].
Unknown-sample challenge
A 25.00 mL sample of an unknown acid (0.05–0.20 M) sits in the flask. Titrate it with 0.100 M NaOH and identify both the acid and its concentration.
- NaOH added
- 0.00 mL
- Drops used
- 0
Your answer
Candidate acids (match the half-equivalence pH against pKa)
How the score works (100 pts)
- Acid identity — 40 pts. Full marks for the right acid.
- Concentration — 40 pts. Shrinks linearly with % error; 0 at 50 % error.
- Endpoint — 10 pts. Reach ≥ 90 % of V_eq; going up to 125 % of V_eq (a few mL past equivalence to see the whole jump) still scores.
- Efficiency — 10 pts. Use ≤ 1.2× the minimum number of drops, and only if you actually reached the equivalence point.
Lab notebook
No readings yet. Run a titration on the bench — every drop is recorded here automatically (or press Log reading on the bench to take a manual reading).
| Run | Time | V titrant (mL) | pH | Indicator | Color | Mode |
|---|
Data & sources
Ka, Kb and Kw values and indicator color-change pH ranges are transcribed from OpenStax, Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley and William R. Robinson (2019): Appendices H and I and Sections 14.1 and 14.7. Licensed under CC BY-NC-SA 4.0 (license). Access for free at openstax.org. Changes: only numeric values were transcribed into this app's own tables; no text, tables, figures or images from the book are reproduced. OpenStax does not endorse this app.
Constants used in this app
| Species | Type | Constant (25 °C) |
|---|
Indicators
| Indicator | Color change | pH range |
|---|
Indicator ranges are the image-derived readings of Figure 14.19 (±0.1 pH; the figure has no numeric labels). Methyl orange uses the corrected 3.2–4.5 range (the page alt text 4.2–6.3 is a known transcription error). Litmus from Figure 14.20.
Solver check: strong acid–strong base (hand-calculable)
25.00 mL of 0.100 M HCl titrated with 0.100 M NaOH at 25 °C.
| NaOH added (mL) | Reference pH | App solver pH | Δ |
|---|
What is computed, not measured
Everything the app computes — pH values, titration curves, derivatives, buffer capacities, challenge samples — is generated in your browser by the exact charge-balance solver. The solver-check reference values are the reviewer's own calculation (2026-09-13), not taken from any textbook. No numbers in this app are presented as University of Idaho measurements; the only external data are the cited OpenStax constants.