Final answer:
Selecting the correct acid-base indicator is essential in titrations, with indicators having a pKin more than 7.0 used for weak acids, and less than 7.0 for weak bases. The titration curves vary significantly with the identity of the compound being titrated, affecting the pH change around the equivalence point.
Step-by-step explanation:
Understanding which acid-base indicator to use during a titration is crucial for accurately determining the equivalence point. In titrations involving strong acids and strong bases, the choice of indicator is quite flexible, with any having a pKin between 4.0 and 10.0 being suitable. However, when titrating a weak acid, the pH at the equivalence point will be above 7.0, necessitating the use of indicators such as phenolphthalein or thymol blue. Conversely, for titrations of a weak base, the pH at the equivalence point will be below 7.0, so indicators like methyl red or bromocresol blue are appropriate. The titration curves for weak acids and bases are influenced by the compound's identity and its dissociation constant (Ka or Kb). The curve shifts slowly around the equivalence point, contrasting with the steeper pH change in strong acid-base titrations.