Which of the following indicators can be used to detect end point in the titration of a weak acid versus…
Which of the following indicators can be used to detect end point in the titration of a weak acid versus strong base?
Methyl red \((4.2\) to \(6.3)\)
Methyl violet \((0.1\) to \(3.2)\)
Methyl orange \((3.1\) to \(4.4)\)
Thymolphthalein \((9.3\) to \(10.5)\)
Solution
In the titration of a weak acid (say, acetic acid) versus strong base (say, sodium hydroxide), the \(\mathrm{pH}\) at the equivalence point is more that 7 due to hydrolysis of congugate base of the weak acid. The steep rise in \(\mathrm{pH}\) around equivalence point encompasses the range 7 to 10 . Thus, thymolphthalein can be used as the indicator to locate end point.
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