A solution contains a single solute (or a mixture) from $NaOH$ , $Na X_{2} CO X_{3}$ , $NaHCO X_{3}$ . On titration with $HCl$ , the volume to the phenolphthalein end point ( $V_{1}$ ) equals the additional volume from there to the methyl orange end point ( $V_{2}$ ), with $V_{1} > 0$ . The solution contains:

Answer: C

Na X_{2} CO X_{3}

consumes equal volumes in both steps (

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

then

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

NaOH

alone gives

V_{2} = 0

NaHCO X_{3}

alone gives

V_{1} = 0

, and

NaOH

and

NaHCO X_{3}

cannot coexist because they react to form

Na X_{2} CO X_{3}