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Chapter 15: Problem 51

Which of the following mixtures would result in buffered solutions when \(1.0 \mathrm{~L}\) of each of the two solutions are mixed? a. \(0.1 \mathrm{M} \mathrm{KOH}\) and \(0.1 \mathrm{M} \mathrm{CH}_{3} \mathrm{NH}_{3} \mathrm{Cl}\) b. \(0.1 \mathrm{M} \mathrm{KOH}\) and \(0.2 \mathrm{M} \mathrm{CH}_{3} \mathrm{NH}_{2}\) c. \(0.2 \mathrm{M} \mathrm{KOH}\) and \(0.1 \mathrm{M} \mathrm{CH}_{3} \mathrm{NH}_{3} \mathrm{Cl}\) d. \(0.1 \mathrm{M} \mathrm{KOH}\) and \(0.2 \mathrm{M} \mathrm{CH}_{3} \mathrm{NH}_{3} \mathrm{Cl}\)

Short Answer

Expert verified
The mixtures (a), (c), and (d) result in buffered solutions when \(1.0 \mathrm{~L}\) of each of the two solutions are mixed.

Step by step solution

01

Identify the substances in each mixture

First, we will identify the substances in each mixture. A buffered solution will contain a weak acid or weak base along with their respective conjugate base or acid. a. KOH (strong base), CH3NH3Cl (weak acid) b. KOH (strong base), CH3NH2 (weak base) c. KOH (strong base), CH3NH3Cl (weak acid) d. KOH (strong base), CH3NH3Cl (weak acid)
02

Analyze each mixture for its buffered properties

We will now determine if each mixture forms a buffered solution or not. Note that a buffered solution should have a weak acid and its conjugate base or a weak base and its conjugate acid. a. The first mixture is KOH and CH3NH3Cl. KOH is a strong base that will react completely with CH3NH3Cl, the weak acid, to form CH3NH2 (weak base) and KCl (salt). That will result in a solution with weak base and its conjugate acid; hence, this mixture will form a buffered solution. b. The second mixture is KOH and CH3NH2. KOH is a strong base that will react partially with CH3NH2, the weak base, to form CH3NH3OH (strong base) and water. There are no conjugate base or acid pairs in this solution; hence, this mixture will not form a buffered solution. c. The third mixture is KOH and CH3NH3Cl. KOH, a strong base, will react completely with CH3NH3Cl, the weak acid, to form CH3NH2 (weak base) and KCl (salt). That will result in a solution with weak base and its conjugate acid; hence, this mixture will form a buffered solution. d. The fourth mixture is KOH and CH3NH3Cl. KOH is a strong base that will react completely with CH3NH3Cl, the weak acid, to form CH3NH2 (weak base) and KCl (salt). That will result in a solution with weak base and its conjugate acid; hence, this mixture will form a buffered solution.
03

Conclusion

From the above analysis, we see that the mixtures (a), (c) and (d) result in buffered solutions when 1.0 L of each of the two solutions are mixed.

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Most popular questions from this chapter

Calculate the pH of each of the following solutions. a. \(0.100 \mathrm{M} \mathrm{HONH}_{2}\left(K_{\mathrm{b}}=1.1 \times 10^{-8}\right)\) b. \(0.100 \mathrm{M} \mathrm{HONH}_{3} \mathrm{Cl}\) c. pure \(\mathrm{H}_{2} \mathrm{O}\) d. a mixture containing \(0.100 \mathrm{M} \mathrm{HONH}_{2}\) and \(0.100 \mathrm{M}\) \(\mathrm{HONH}_{3} \mathrm{Cl}\)

Phosphate buffers are important in regulating the \(\mathrm{pH}\) of intracellular fluids at \(\mathrm{pH}\) values generally between \(7.1\) and \(7.2\). a. What is the concentration ratio of \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) to \(\mathrm{HPO}_{4}{ }^{2-}\) in intracellular fluid at \(\mathrm{pH}=7.15\) ? \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}(a q) \rightleftharpoons \mathrm{HPO}_{4}^{2-}(a q)+\mathrm{H}^{+}(a q) \quad K_{\mathrm{a}}=6.2 \times 10^{-8}\) b. Why is a buffer composed of \(\mathrm{H}_{3} \mathrm{PO}_{4}\) and \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) ineffective in buffering the \(\mathrm{pH}\) of intracellular fluid? \(\mathrm{H}_{3} \mathrm{PO}_{4}(a q) \rightleftharpoons \mathrm{H}_{2} \mathrm{PO}_{4}^{-}(a q)+\mathrm{H}^{+}(a q) \quad K_{\mathrm{a}}=7.5 \times 10^{-3}\)

Derive an equation analogous to the Henderson-Hasselbalch equation but relating \(\mathrm{pOH}\) and \(\mathrm{p} K_{\mathrm{b}}\) of a buffered solution composed of a weak base and its conjugate acid, such as \(\mathrm{NH}_{3}\) and \(\mathrm{NH}_{4}^{+} .\)

Potassium hydrogen phthalate, known as KHP (molar mass = \(204.22 \mathrm{~g} / \mathrm{mol}\) ), can be obtained in high purity and is used to determine the concentration of solutions of strong bases by the reaction $$\mathrm{HP}^{-}(a q)+\mathrm{OH}^{-}(a q) \longrightarrow \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{P}^{2-}(a q)$$ If a typical titration experiment begins with approximately \(0.5 \mathrm{~g}\) KHP and has a final volume of about \(100 \mathrm{~mL}\), what is an appropriate indicator to use? The \(\mathrm{p} K_{\mathrm{a}}\) for \(\mathrm{HP}^{-}\) is \(5.51\).

A \(0.210-\mathrm{g}\) sample of an acid (molar mass \(=192 \mathrm{~g} / \mathrm{mol}\) ) is titrated with \(30.5 \mathrm{~mL}\) of \(0.108 \mathrm{M} \mathrm{NaOH}\) to a phenolphthalein end point. Is the acid monoprotic, diprotic, or triprotic?
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