Chemistry: A Molecular Approach (3rd Edition)

Published by Prentice Hall
ISBN 10: 0321809246
ISBN 13: 978-0-32180-924-7

Chapter 16 - Sections 16.1-16.8 - Exercises - Problems by Topic - Page 804: 54e

Answer

This mixture results in a buffer.

Work Step by Step

$$HCl(aq) + CH_3NH_2(aq) \rightarrow CH_3{NH_3}^+(aq) + Cl^-(aq)$$ $CH_3NH_2$ and $CH_3N{H_3}^{+}$ is a conjugate acid-base pair. Therefore, if a certain quantity of $CH_3NH_2$ remains in solution, it will act as a buffer. In order for this to happen, $CH_3NH_2$ must be the excess reactant. Calculate the number of moles of each compound: $$HCl: 95.0 \space mL \times \frac{0.10 \space M}{1 \space L} \times \frac{1 \space L}{1000 \space mL} = 0.0095 \space mole$$ $$CH_3NH_2: 105.0 \space mL \times \frac{0.15 \space M}{1 \space L} \times \frac{1 \space L}{1000 \space mL} = 0.01575 \space mole$$ $0.01575 \gt 0.0095$. $CH_3NH_2$ is the excess reactant. Therefore, this mixture will result in a buffer.
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