Titration Curves: pH vs Volume for the Four Classic Titrations
Explore four classic titration curves: strong acid + strong base, weak acid + strong base, weak base + strong acid, and strong base + strong acid. Each uses 25.00 mL of 0.100 M analyte and 0.100 M titrant. Read the pH at any volume and compare eight indicator transition ranges.
Locating equivalence points and buffer regions, and choosing an indicator per titration type.
25.00 mL of 0.100 M analyte titrated with 0.100 M titrant (the comparison setup).
The equivalence-point pH is 7 only for strong acid + strong base; weak systems land above or below 7.
Swipe horizontally to see the full chart.
Selected pH Values
Milestone values from each curve, including the initial solution, half-equivalence, equivalence, and excess-titrant regions. Use the interactive chart to inspect intermediate volumes.
| 0.00 | 1.00 | 2.87 | 11.12 | 13.00 |
| 5.00 | 1.18 | 4.14 | 9.86 | 12.82 |
| 12.50 | 1.48 | 4.74 | 9.26 | 12.52 |
| 20.00 | 1.95 | 5.35 | 8.65 | 12.05 |
| 24.00 | 2.69 | 6.13 | 7.87 | 11.31 |
| 24.90 | 3.70 | 7.14 | 6.86 | 10.30 |
| 25.00 | 7.00 | 8.72 | 5.28 | 7.00 |
| 25.10 | 10.30 | 10.30 | 3.70 | 3.70 |
| 26.00 | 11.29 | 11.29 | 2.71 | 2.71 |
| 30.00 | 11.96 | 11.96 | 2.04 | 2.04 |
| 37.50 | 12.30 | 12.30 | 1.70 | 1.70 |
| 50.00 | 12.52 | 12.52 | 1.48 | 1.48 |
Important Notes
- Every curve uses the same comparison setup: 25.00 mL of 0.100 M analyte titrated with 0.100 M titrant, so the equivalence point falls at 25.00 mL in all four cases.
- For the weak-acid curve, the half-equivalence point occurs at 12.50 mL and pH = pKa = 4.74. For the weak-base curve, pH equals the pKa of NH4+ at half-equivalence, giving pH 9.26.
- Charge-balance calculations and standard shortcut methods can differ by 0.01 pH unit because of rounding. For example, the initial pH of 0.100 M acetic acid may appear as 2.87 or 2.88 depending on when values are rounded.
- Equivalence-point pH depends on the titration type: 7.00 for strong + strong, 8.72 for the weak acid because the conjugate base hydrolyzes, and 5.28 for the weak base because the conjugate acid hydrolyzes.
- Choose an indicator whose full color-change interval lies inside the steep region of the curve. The transition range does not need to contain the exact equivalence-point pH when the steep region is broad.
- Phenolphthalein (pH 8.3 to 10.0) fits the weak-acid curve. Methyl orange (pH 3.1 to 4.4) changes too early on that curve. On the weak-base curve, methyl orange lies near the lower edge of the steep drop, while methyl red or bromocresol green is a closer match.
- The steep central rise of the strong + strong curve spans roughly pH 3 to 11 within a fraction of a milliliter, which is why almost any indicator works there.
- These curves are a general reference. Individual titration problems supply their own volumes and concentrations.
Verification references: Calculated from Ka = Kb = 1.8 × 10-5 and Kw = 1.0 × 10-14 at 25 °C using charge-balance equations.