An indicator is weak acid (or base) having a conjugate base (or acid) with a significantly different colour. For the titration of a weak base, how would you choose an appropriate indicator?
1)Choose an indicator that has a pKb close to pKb of the base
2)Choose an indicator which changes colour anywhere in the pH range 0-7
3)Choose an indicator that has a pKa close to pKb of the base
4)Choose an indicator with a pKb close to the pH of the titration at equivalence
5)Choose an indicator with a pKa close to the pH of the titration at equivalence
Acid-base indicators, the Substances such as phenolphthalein, which can be used to determine the pH of a solution.