Chemistry: The Central Science (13th Edition)

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

Chapter 16 - Acid-Base Equilibria - Additional Exercises - Page 721: 16.106

Answer

$pH \approx 5.4$ No, that number doesn't make sense because NaOH is a base. We normally disconsider the concentration of $[H^+]$ and $[OH^-], which we can't do in this case.

Work Step by Step

1. Find the pH, by the normal formula: $pOH = -log[OH^-]$ $pOH = -log(2.5 \times 10^{-9})$ $pOH = 8.6$ $pH = 14 - pOH$ $pH = 5.4$ 2. Since $NaOH$ is a base, we expect that the pH will be higher than 7, so 5.4 doesn't make sense. 3. If we consider the concentration of $[OH^-]$ in pure water: $pOH = -log((2.5 \times 10^{-9})+(10^{-7}))$ $pOH = 6.99$ $pH = 7.01$ And that number is compatible with a base solution.
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