What is an indicator and why is it used in the titration?View keyboard shortcutsEditViewInsertFormatToolsTable12ptParagraph

An indicator is a substance that changes color in response to a chemical change. An acid-base indicator (e.g., phenolphthalein) changes color depending on the pH.

Titration is a technique where a solution of known concentration is used to determine the concentration of an unknown solution.

The purpose of the indicator is to show when enough titrant has been added to completely react with the substance being titrated. This is called the endpoint of the titration.

Here's a step-by-step explanation:

1. The solution to be tested (the analyte) is prepared in a beaker or Erlenmeyer flask.

2. The indicator is added to the analyte.

3. The titrant, a solution of known concentration, is carefully added to the analyte, drop by drop, from a burette.

4. As the titrant is added, it reacts with the analyte. The indicator changes color to show that the reaction is occurring.

5. The titration continues until the indicator changes color, showing that all the analyte has reacted with the titrant. This is the endpoint of the titration.

6. The volume of titrant that was required to reach the endpoint is noted. This volume, along with the known concentration of the titrant, is used to calculate the concentration of the analyte.

In summary, an indicator is used in titration to show when the reaction between the analyte and the titrant is complete. Without an indicator, it would be difficult to know when to stop adding the titrant and the results of the titration would be less accurate.