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JEE Main levelSingle correct optionDifficulty 2 of 3sb191

25.0 mL of 0.100 M $Na X_{2} CO X_{3}$ is titrated with 0.100 M HCl using phenolphthalein as the indicator. The volume of HCl at the end point is

A12.5 mL
B37.5 mL
C50.0 mL
D25.0 mL

Answer: D

Phenolphthalein changes colour when carbonate has been converted to hydrogencarbonate:

CO X_{3} X^{2 -} + H X^{+} HCO X_{3} X^{-}

. Moles of HCl equal moles of carbonate,

0.100 \times 25.0

mmol, so the volume is 25.0 mL.

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