Select your acid, base, normality and indicator — then open the burette valve and watch the titration unfold in real time, with live pH tracking and equivalence point calculation.
Acid-base titration is a fundamental quantitative analytical technique in chemistry used to determine the unknown concentration (or normality) of an acid or base by neutralising it with a standard solution of known normality. The point at which the acid and base completely neutralise each other is called the equivalence point. The point at which the indicator changes colour is called the endpoint — ideally these coincide.
The governing equation for all titrations is: N₁V₁ = N₂V₂, where N₁ and V₁ are the normality and volume of the titrant, and N₂ and V₂ are the normality and volume of the analyte. Using this, the unknown normality of the analyte can be calculated once the equivalence volume is known.
When a strong acid (HCl, H₂SO₄, HNO₃) is titrated against a strong base (NaOH, KOH), the equivalence point occurs at exactly pH 7 at 25°C. Before the equivalence point, the pH rises slowly (buffer region) and then sharply rises near the equivalence point — this creates the characteristic S-shaped pH curve. Both phenolphthalein (endpoint pH 8.3–10) and methyl orange (endpoint pH 3.1–4.4) can be used, though phenolphthalein gives a cleaner colour change from colourless to pink.
When a weak acid (CH₃COOH — acetic acid) is titrated against a strong base, the equivalence point falls above pH 7 (typically around pH 8–9) due to hydrolysis of the salt formed. A buffer region exists in the middle of the titration (Henderson-Hasselbalch region). Phenolphthalein is the suitable indicator for this combination. Methyl orange is not suitable as its endpoint (pH ~4) falls in the buffer region, far from the equivalence point.
When a strong acid is titrated against a weak base (NH₃, Na₂CO₃), the equivalence point falls below pH 7 (typically pH 5–6). Methyl orange or methyl red are suitable indicators for this combination. Phenolphthalein is not suitable as its endpoint lies above pH 7, past the equivalence point.
The correct choice of indicator is critical for an accurate titration. The indicator's endpoint pH must fall within the steep vertical region of the pH curve — this ensures the colour change occurs exactly at or very near the equivalence point. Using an incorrect indicator (e.g., methyl orange for weak acid–strong base) results in significant titration error.
The equivalence point is the theoretical point where moles of acid exactly equal moles of base (or equivalents are equal). The endpoint is the practical point where the indicator changes colour, signalling the completion of the titration. In a well-designed experiment with the correct indicator, the endpoint and equivalence point are extremely close, minimising titration error.
Acid-base titration is a core experiment in the Kerala University FYUGP Chemistry laboratory. Students perform volumetric analysis using standard NaOH or HCl solutions to determine the normality of unknown acids or bases. The experiment tests understanding of the N₁V₁ = N₂V₂ formula, choice of indicator, endpoint detection, and burette reading. This simulation allows FYUGP students to practise the full titration procedure virtually before entering the lab.