What is the pH at the equivalence point for the titration of 0.20 M solutions of the following acids and bases? Which of the indicators in Figure 17.5 would be suitable for each titration? (c) Ba(OH)2 and HBr

Verified step by step guidance

1. Step 1: Identify the type of titration. Ba(OH)2 is a strong base and HBr is a strong acid, so this is a strong acid-strong base titration.
2. Step 2: Determine the pH at the equivalence point. For a strong acid-strong base titration, the pH at the equivalence point is 7 because the salt formed (BaBr2) does not hydrolyze.
3. Step 3: Refer to the table of indicators to find an indicator that changes color around pH 7.
4. Step 4: From the table, bromothymol blue has a pH range of 6.0 - 7.6, making it suitable for detecting the equivalence point at pH 7.
5. Step 5: Conclude that bromothymol blue is the appropriate indicator for the titration of Ba(OH)2 and HBr.

Key Concepts

pH and the Equivalence Point

The pH at the equivalence point in a titration is the point at which the amount of titrant added is stoichiometrically equivalent to the amount of substance in the sample. For strong acid-strong base titrations, this point typically occurs at pH 7. However, for weak acid-strong base or strong acid-weak base titrations, the pH can vary significantly due to the nature of the acid or base involved.

Indicators in Titration

Indicators are substances that change color at a specific pH range, making them useful for determining the endpoint of a titration. The choice of indicator depends on the pH at the equivalence point of the titration; it should change color at or near this pH to provide a clear visual cue for the completion of the reaction.

Strong Base and Strong Acid Reaction

In the titration of a strong base like Ba(OH)2 with a strong acid like HBr, the reaction produces water and a salt. The resulting solution at the equivalence point will have a neutral pH of around 7, as both the acid and base completely dissociate in solution. Understanding this reaction is crucial for predicting the pH and selecting appropriate indicators.