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

검증된 단계별 안내

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.

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.

Step 3: Refer to the table of indicators to find an indicator that changes color around pH 7.

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.

Step 5: Conclude that bromothymol blue is the appropriate indicator for the titration of Ba(OH)2 and HBr.

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주요 개념

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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.