$Na X_{2} CO X_{3}$ (molar mass $106 g mo l^{- 1}$ ) is titrated with $HCl$ and the titration is stopped at the phenolphthalein end point, where only $CO X_{3} X^{2 -} HCO X_{3} X^{-}$ has occurred. The equivalent mass of $Na X_{2} CO X_{3}$ in this titration is:

Answer: B

Only one

H X^{+}

is taken up per carbonate ion (

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

), so

n = 1

. Equivalent mass

= 106/1 = 106

, not 53 (53 applies to the methyl orange end point).