Question detail
What is the role of an indicator in an acid-base titration?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
A-level practical endorsement and required practical activities
Question
- A. To change color at a specific pH
- B. To neutralize the acid
- C. To increase the temperature of the solution
- D. To measure the volume of the solution
Answer
To change color at a specific pH
Explanation
The correct option is To change color at a specific pH. To change color at a specific pH is the best answer because it directly supports the AQA A-Level Chemistry objective to required practical 9: investigate pH changes in acid-base titrations. This reasoning is anchored to A-level required practical activities in A-level practical endorsement and required practical activities, and it separates titration from similar A-Level ideas rather than relying on a vague recall statement. Other options are weaker if they use the wrong evidence, calculation, mechanism, observation, unit, or conclusion for this subtopic.
Common mistake
pH Calculation Mistake
Students often forget to convert the volume of acid or base used in titration to the correct units before calculating pH changes.
Always ensure that the volume is in dm³ when using the formula for pH calculation. For example, if you have 25 cm³ of a solution, convert it to dm³ by dividing by 1000. Then, use the formula pH = -log[H⁺] to find the pH, substituting the concentration of H⁺ ions after the titration. Keep the correction anchored to A-level required practical activities and the objective: Required practical 9: investigate pH changes in acid-base titrations.
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