Acid-Base Indicators: Mechanism
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An acid-base indicator is a weak acid or base whose protonated and deprotonated forms differ visibly in color, so solution pH sets which color appears.
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Methyl orange's protonated form appears red, its deprotonated form yellow, shifting as pH crosses its equilibrium.
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An indicator changes color at its own equilibrium, not necessarily at a titration's equivalence point.