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.
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.
Source:
- Calculated from Ka = Kb = 1.8 × 10⁻⁵ and Kw = 1.0 × 10⁻¹⁴ at 25 °C using charge-balance equations