Problem 39
Calculate the pH of each of the following buffered solutions. $$ \begin{array}{l}{\text { a. } 0.10 M \text { acetic acid0.25 } M \text { sodium acetate }} \\ {\text { b. } 0.25 M \text { acetic acid/0.10 } M \text { sodium acetate }}\end{array} $$ $$ \begin{array}{l}{\text { c. } 0.080 M \text { acetic acid/0.20 } M \text { sodium acetate }} \\ {\text { d. } 0.20 M \text { acetic acid/0.080 } M \text { sodium acetate }}\end{array} $$
Problem 42
A buffered solution is made by adding 50.0 \(\mathrm{g} \mathrm{NH}_{4} \mathrm{Cl}\) to 1.00 \(\mathrm{L}\) of a \(0.75-\mathrm{M}\) solution of \(\mathrm{NH}_{3}\) . Calculate the \(\mathrm{pH}\) of the final solution. (Assume no volume change.)
Problem 43
Calculate the pH after 0.010 mole of gaseous HCl is added to 250.0 \(\mathrm{mL}\) of each of the following buffered solutions. $$ \begin{array}{l}{\text { a. } 0.050 M \mathrm{NH}_{3} / 0.15 \mathrm{MNH}_{4} \mathrm{Cl}} \\ {\text { b. } 0.50 \mathrm{M} \mathrm{NH}_{3} / 1.50 \mathrm{M} \mathrm{NH}_{4} \mathrm{Cl}}\end{array} $$ Do the two original buffered solutions differ in their pH or their capacity? What advantage is there in having a buffer with a greater capacity?
Problem 44
Calculate the pH after 0.15 mole of solid NaOH is added to 1.00 \(\mathrm{L}\) of each of the following solutions: a. 0.050\(M\) propanoic acid \(\left(\mathrm{HC}_{3} \mathrm{H}_{5} \mathrm{O}_{2}, K_{2}=1.3 \times 10^{-5}\right)\) and 0.080\(M\) sodium propanoate b. 0.50\(M\) propanoic acid and 0.80\(M\) sodium propanoate c. Is the solution in part a still a buffer solution after the NaOH has been added? Explain.
Problem 45
Some \(\mathrm{K}_{2} \mathrm{SO}_{3}\) and \(\mathrm{KHSO}_{3}\) are dissolved in 250.0 \(\mathrm{mL}\) of solution and the resulting \(\mathrm{pH}\) is \(7.25 .\) Which is greater in this buffer solution, the concentration of \(\mathrm{SO}_{3}^{2-}\) or the concentration of \(\mathrm{HSO}_{3}-7\) If \(\left[\mathrm{SO}_{3}^{2-}\right]=1.0 \mathrm{M}\) in this solution, calculate the concentration of \(\mathrm{HSO}_{3}\) .
Problem 47
Calculate the mass of sodium acetate that must be added to 500.0 \(\mathrm{mL}\) of 0.200\(M\) acetic acid to form a \(\mathrm{pH}=5.00\) buffer solution.
Problem 48
What volumes of 0.50 \(\mathrm{M} \mathrm{HNO}_{2}\) and 0.50 \(\mathrm{M}\) NaNO, must be mixed to prepare 1.00 \(\mathrm{L}\) of a solution buffered at \(\mathrm{pH}=3.55 ?\)
Problem 51
Carbonate buffers are important in regulating the pH of blood at \(7.40 .\) If the carbonic acid concentration in a sample of blood is 0.0012 M, determine the bicarbonate ion concentration required to buffer the pH of blood at pH \(=7.40\) $$ \mathrm{H}_{2} \mathrm{CO}_{3}(a q) \rightleftharpoons \mathrm{HCO}_{3}^{-}(a q)+\mathrm{H}^{+}(a q) \quad K_{\mathrm{a}}=4.3 \times 10^{-7} $$
Problem 58
Which of the following mixtures would result in a buffered solution when 1.0 \(\mathrm{L}\) of each of the two solutions are mixed? $$ \begin{array}{l}{\text { a. } 0.2 M \mathrm{HNO}_{3} \text { and } 0.4 \mathrm{M} \mathrm{NaNO}_{3}} \\ {\text { b. } 0.2 \mathrm{M} \mathrm{HNO}_{3} \text { and } 0.4 \mathrm{M} \mathrm{HF}}\end{array} $$ $$ \begin{array}{l}{\text { c. } 0.2 M \mathrm{HNO}_{3} \text { and } 0.4 \mathrm{M} \mathrm{NaF}} \\ {\text { d. } 0.2 \mathrm{M} \mathrm{HNO}_{3} \text { and } 0.4 \mathrm{M} \mathrm{NaOH}}\end{array} $$
Problem 60
Calculate the number of moles of \(\mathrm{HCl}(g)\) that must be added to 1.0 \(\mathrm{L}\) of 1.0 \(\mathrm{M} \mathrm{NaC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\) to produce a solution buffered at each pH. $$ \text{(a)}\mathrm{pH}=\mathrm{p} K_{\mathrm{a}} \quad \text { b. } \mathrm{pH}=4.20 \quad \text { c. } \mathrm{pH}=5.00 $$
