An acid-base titration curve plots pH vs. volume of titrant added, revealing the buffer region, half-equivalence point (where pH = pKa), and equivalence point. Unlike a numeric titration calculator, this tool generates the complete sigmoid curve for visual analysis of strong, weak, and polyprotic acid-base systems.
Titration Setup
Quick Presets
Analyte (in flask)
Titrant (in burette)
pH vs. Volume of Titrant
Equations
How to Use the Acid-Base Titration Curve Generator
The acid-base titration curve generator plots pH vs. volume of titrant, revealing the complete shape of the titration curve. Unlike a simple endpoint calculator, this tool shows the buffer region, half-equivalence point, and the steep pH jump at the equivalence point.
Step 1: Choose a Preset or Configure Manually
Start with a preset: HCl + NaOH for a classic strong acid-strong base titration, acetic acid + NaOH (CH₃COOH + NaOH) for a weak acid-strong base titration that shows a buffer region, or H₃PO₄ + NaOH for a polyprotic acid with multiple equivalence points. Or configure your own by selecting analyte type, concentration, volume, and titrant.
Step 2: Read the Titration Curve
The S-shaped (sigmoid) curve shows pH rising as titrant is added. For a strong acid-strong base system, the sigmoid is symmetric around pH 7. For a weak acid-strong base system (e.g., 0.1 M acetic acid titrated with 0.1 M NaOH), the initial pH is higher (~2.87 instead of 1.0 for HCl), the buffer region spans roughly pH 3.75–5.75, the half-equivalence point is at pH 4.75 (= pKa of acetic acid), and the equivalence point is above pH 7 (~pH 8.7) because acetate ion hydrolyzes water.
Understanding the Equivalence Point
The vertical dashed red line marks the equivalence point — the volume at which moles of titrant exactly neutralize moles of analyte (V_eq = C_a × V_a / C_t). For HCl + NaOH with identical concentrations and volumes, V_eq = 50 mL. The equivalence point pH is: 7.0 (strong/strong), above 7 (weak acid/strong base, due to conjugate base hydrolysis), below 7 (strong acid/weak base).
The Half-Equivalence Point and pKa
For weak acid titrations, the amber dashed line marks the half-equivalence point where exactly half the acid has been neutralized. At this point, [HA] = [A⁻], so the Henderson-Hasselbalch equation gives pH = pKa + log(1) = pKa. This is how chemists experimentally measure pKa — read the pH at the half-equivalence point from the curve.
For a detailed walkthrough, see our guide: Acid-Base Reactions Explained.
FAQ
Is the Titration Curve Generator free?
Yes, completely free. No signup or account needed. All pH calculations and chart rendering happen in your browser using Chart.js.
Is my data private?
Yes. All calculations run locally in your browser. No data is sent to any server.
What is the difference between this tool and the Titration Calculator?
The Titration Calculator computes a single equivalence point volume numerically. This tool generates the complete pH vs. volume curve, showing the buffer region, half-equivalence point (pH = pKa), and equivalence point across the entire titration range using Chart.js visualization.
Why does the pH change slowly in the buffer region?
During a weak acid/strong base titration, the buffer region occurs when both the weak acid and its conjugate base are present simultaneously. The Henderson-Hasselbalch equation (pH = pKa + log[A-]/[HA]) governs this region. Maximum buffer capacity is at the half-equivalence point where [A-] = [HA] and pH = pKa.
What is the pH at the equivalence point of a strong acid-strong base titration?
For a strong acid-strong base titration (e.g., HCl + NaOH), the equivalence point is exactly pH 7.00 at 25°C because the resulting solution is pure water. For weak acid-strong base, the equivalence point is above pH 7 because the conjugate base hydrolyzes water.
What is the half-equivalence point?
At the half-equivalence point (halfway to the equivalence point), exactly half of the weak acid has been converted to its conjugate base. At this point, [HA] = [A-], so log(1) = 0 in Henderson-Hasselbalch, and pH = pKa. This is why the half-equivalence point is used to experimentally determine pKa.
Can this tool handle polyprotic acid titrations?
Yes. Phosphoric acid (H3PO4) and carbonic acid (H2CO3) are included with multiple pKa values. The tool plots multiple equivalence points and buffer regions corresponding to each successive proton transfer.