How do you choose the right indicator for a titration?

Choosing the right indicator for a titration is important because it shows the end point of the reaction accurately. Here’s how to choose it simply:

1. Know the type of titration:
   • Acid-base titration: The indicator should change color near the pH where the reaction is complete.
     • Strong acid vs strong base → use methyl orange or phenolphthalein (any works well).
     • Strong acid vs weak base → use methyl orange (end point at low pH).
     • Weak acid vs strong base → use phenolphthalein (end point at higher pH).
2. Check the pH range of the indicator:
   • The indicator changes color in a certain pH range.
   • Choose one whose color change happens at or near the equivalence point of the titration.
3. Consider the type of reaction:
   • Redox titration: Use an indicator that changes color when oxidation or reduction occurs (like starch for iodine titrations).
   • Complexometric titration: Use an indicator that forms a colored complex with the metal ion (like Eriochrome Black T for calcium or magnesium).
4. Avoid ambiguous color changes:
   • The indicator’s color change should be sharp and easy to see to prevent errors.

In short:
Choose an indicator whose color change occurs at the end point of the reaction, matches the type of titration, and is easy to observe.