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Unformatted text preview: bottle? b) Write out the reaction for NaOH with CO 2 . S16 - Phenolphthalein is used as a basic indicator. Below about pH 9, it is colorless, and above pH 9 it turns pink. A friend of yours in Chem 213 has come to you for help. She noticed that the phenolphthalein endpoint was not stable; several times she titrated an acid solution until it became basic enough for the solution to just turn pink, but in every case the color faded after a few minutes. Given that phenolphthalein is stable, that the titration reaction is rapid, that she stirred her solution throughout the titration, and that the flask was left open to the air, what would you tell your friend is causing her solution to change?...
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- Fall '10