Which indicator is preferred for the titration of a weak acid with a strong base?
ABromothymol blue
BBromocresol green
CPhenolphthalein
DUniversal indicator
Answer & Solution
Correct answer: C. Phenolphthalein
1. The solution at the end point of a titration is not always neutral.
2. A weak acid neutralised by a strong base leaves a solution that is slightly basic.
3. The indicator must change colour over the pH range where that end point falls.
4. Phenolphthalein changes from colourless to pink across the range that suits a weak acid with a strong base.
5. Bromothymol blue suits a strong acid with a strong base, and bromocresol green suits a strong acid with a weak base.
_Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 9: Acids and bases_
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