Chemistry: The Molecular Science (5th Edition)

Published by Cengage Learning
ISBN 10: 1285199049
ISBN 13: 978-1-28519-904-7

Chapter 15 - Additional Aqueous Equilibria - Questions for Review and Thought - Topical Questions - Page 693a: 18d


$HC{O_3}^-$ and $C{O_3}^{2-}$ are capable of making a buffer with $9.7 \times 10^{-11}M$ of $H_3O^+$ This happens because the $K_a$ value for $HC{O_3}^-$ is close to this hydronium ion concentration value.

Work Step by Step

1. Analyze the $[H_3O^+] (9.7 \times 10^{-11}M)$, and find the conjugate acid-base pair with the closest $K_a$ value. - Use Table $15-1$ on page $659$. - $HC{O_3}^-$ and $C{O_3}^{2-}$: $K_a$ = $4.7 \times 10^{-11}$ Therefore, this is the best pair that can be used to make a buffer with hydronium ion concentration equal to $9.7 \times 10^{-11}M.$
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