Indicators

Definition

Indicators are substances that change color at a specific pH level, used to determine the endpoint of a titration. They help in identifying the equivalence point in chemical reactions.

5 Must Know Facts For Your Next Test

1. Indicators are crucial for determining the completion of acid-base titrations.
2. Common indicators include phenolphthalein, which turns pink in basic solutions, and methyl orange, which turns red in acidic solutions.
3. The choice of indicator depends on the expected pH range at the equivalence point of the reaction.
4. Indicators function due to their weak acid or base nature, undergoing a visible color change when they ionize.
5. An indicator's transition range is typically within one or two pH units where it changes color.

Review Questions

• What is the role of an indicator in a titration?
• Why is phenolphthalein commonly used as an indicator in acid-base titrations?
• How does the choice of indicator affect the accuracy of determining the equivalence point?

Related terms

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

Equivalence Point: The point in a titration at which the added titrant is chemically equivalent to the analyte in the sample.

pH: A scale used to specify how acidic or basic a water-based solution is.