Question

How to choose an indicator for an acid base titration?

Answer 1

Titration:

• An acid-base titration is an experimental technique used to determine the strength and concentration of acid and base in a solution.
• In titration measured volume of acid or base of known molarity is added to acid and base of unknown molarity until neutralization occurs.

Indicators used for an acid base titration.

• Phenolphthalein – Colourless /(acid) and pink (alkali)
• Methyl orange – Pink (acid) and yellow (alkali)
• The titration curves for other combinations of strong/weak acid/base pairs offer a more limited change in pH.
• Phenolphthalein works in the pH range of 8.2 to 10, and methyl orange works in the acidic range of 3.1 to 4.1.
• Any indicator with a range between pH 11 and pH 3 may be used, for acid base titration.

Therefore, Phenolphthalein and Methyl orange can be used for acid-base titration.