Determine the equivalence point volume and the pH expected there.
Titrating a weak acid with a strong base gives an equivalence pH above 7, because the conjugate base hydrolyses. The indicator must change colour across that pH, which is why phenolphthalein suits weak-acid titrations and methyl red does not. Assuming equivalence occurs at pH 7 leads to the wrong indicator and a systematic titration error.
Equivalence Point
Equivalence pH for a weak acid comes from hydrolysis of its conjugate base at the diluted concentration
Equivalence pH for a weak acid comes from hydrolysis of its conjugate base at the diluted concentration Titrating a weak acid with a strong base gives an equivalence pH above 7, because the conjugate base hydrolyses. The indicator must change colour across that pH, which is why phenolphthalein suits weak-acid titrations and methyl red does not.
Assuming equivalence occurs at pH 7 leads to the wrong indicator and a systematic titration error.
This calculator takes 4 inputs: Analyte volume, Analyte concentration, Titrant concentration, pKa of the weak analyte. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.