91Ó°ÊÓ

Does the pH of the solution increase, decrease, or stay the same when you (a) Add solid ammonium chloride to a dilute aqueous solution of \(\mathrm{NH}_{3} ?\) (b) Add solid sodium acetate to a dilute aqueous solution of acetic acid? (c) Add solid NaCl to a dilute aqueous solution of NaOH?

Does the pH of the solution increase, decrease, or stay the same when you (a) Add solid sodium oxalate, \(\mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4},\) to \(50.0 \mathrm{mL}\) of \(0.015 \mathrm{M}\) oxalic acid, \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} ?\) (b) Add solid ammonium chloride to 75 mL of \(0.016 \mathrm{M}\) HCl? (c) Add \(20.0 \mathrm{g}\) of \(\mathrm{NaCl}\) to \(1.0 \mathrm{L}\) of \(0.10 \mathrm{M}\) sodium acetate, \(\mathrm{NaCH}_{3} \mathrm{CO}_{2} ?\)

What is the pH of 0.15 M acetic acid to which 1.56 g of sodium acetate, \(\mathrm{NaCH}_{3} \mathrm{CO}_{2}\) has been added?

What is the pH of the solution that results from adding \(25.0 \mathrm{mL}\) of \(0.12 \mathrm{M} \mathrm{HCl}\) to \(25.0 \mathrm{mL}\) of \(0.43 \mathrm{M} \mathrm{NH}_{3} ?\)

Lactic acid (CH \(_{3} \mathrm{CHOHCO}_{2} \mathrm{H}\) ) is found in sour milk, in sauerkraut, and in muscles after activity (see page 479 ). \(\left(K_{\mathrm{a}} \text { for lactic acid }=1.4 \times 10^{-4} .\right)\) (a) If 2.75 g of \(\mathrm{NaCH}_{3} \mathrm{CHOHCO}_{2},\) sodium lactate, is added to \(5.00 \times 10^{2} \mathrm{mL}\) of \(0.100 \mathrm{M}\) lactic acid, what is the \(\mathrm{pH}\) of the resulting buffer solution? (b) Is the final pH lower or higher than the pH of the lactic acid solution?

Calculate the pH of a solution that has an acetic acid concentration of \(0.050 \mathrm{M}\) and a sodium acetate concentration of \(0.075 \mathrm{M}.\)

Which of the following combinations would be the best to buffer the pH of a solution at approximately \(9 ?\) (a) HCl and NaCl (b) \(\mathrm{NH}_{3}\) and \(\mathrm{NH}_{4} \mathrm{Cl}\) (c) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\) and \(\mathrm{NaCH}_{3} \mathrm{CO}_{2}\)

Which of the following combinations would be the best choice to buffer the \(\mathrm{pH}\) of a solution at approximately \(7 ?\) (a) \(\mathrm{H}_{3} \mathrm{PO}_{4}\) and \(\mathrm{NaH}_{2} \mathrm{PO}_{4}\) (b) \(\mathrm{NaH}_{2} \mathrm{PO}_{4}\) and \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\) (c) \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\) and \(\mathrm{Na}_{3} \mathrm{PO}_{4}\)

Describe how to prepare a buffer solution from \(\mathrm{NaH}_{2} \mathrm{PO}_{4}\) and \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\) to have a \(\mathrm{pH}\) of 7.5

You dissolve \(0.425 \mathrm{g}\) of \(\mathrm{NaOH}\) in \(2.00 \mathrm{L}\) of a buffer solution that has \(\left[\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\right]=\left[\mathrm{HPO}_{4}^{2-}\right]=0.132 \mathrm{M} .\) What is the pH of the solution before adding NaOH? After adding NaOH?