Chemistry: The Central Science (13th Edition)

Published by Prentice Hall
ISBN 10: 0321910419
ISBN 13: 978-0-32191-041-7

Chapter 17 - Additional Aspects of Aqueous Equilibria - Exercises - Page 769: 17.37a

Answer

The pH at the equivalence point of that titration is above 7.

Work Step by Step

$NaHCO_3$ is a strong electrolyte, therefore, it is completely dissociated in: $Na^+$ and $HCO_3^-$. That last one can act as an acid if $NaOH$ is added to the solution. That reaction can be described by the equation: $NaHCO_3 (aq) + NaOH(aq) -- \gt Na_2CO_3(aq) + H_2O(l)$ At the equivalence point, all the $NaHCO_3$ and $NaOH$ is consumed, and the only remaining compounds are $Na_2CO_3$ and $H_2O$. Since $Na_2CO_3$ is also a strong electrolyte, the $CO_3^{2-}$ ion will be present in the solution. $CO_3^{2-}$ acts as a base in water, therefore, the pH at the equivalence point is basic. pH $\gt$ 7. The $Na^+$ ions and the water will not affect the pH of the solution.
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