Chapter 16

A \(0.015-M\) solution of a monoprotic acid is 0.92 percent ionized. Calculate the ionization constant for the acid.

Calculate the concentration at which a monoprotic acid with \(K_{\mathrm{a}}=4.5 \times 10^{-5}\) will be 2.5 percent ionized.

Calculate the \(K_{\mathrm{a}}\) of a weak acid if a \(0.19-M\) aqueous solution of the acid has a \(\mathrm{pH}\) of 4.52 at \(25^{\circ} \mathrm{C}\).

The \(\mathrm{pH}\) of an aqueous acid solution is 6.20 at \(25^{\circ} \mathrm{C}\). Calculate the \(K_{\mathrm{a}}\) for the acid. The initial acid concentration is \(0.010 \mathrm{M}\).

What is the original molarity of a solution of formic acid \((\mathrm{HCOOH})\) whose \(\mathrm{pH}\) is 3.26 at \(25^{\circ} \mathrm{C} ?\left(K_{\mathrm{a}}\right.\) for $$ \text { formic acid } \left.=1.7 \times 10^{-4} .\right) $$

What is the original molarity of a solution of a weak acid whose \(K_{\mathrm{a}}\) is \(3.5 \times 10^{-5}\) and whose \(\mathrm{pH}\) is 5.26 at \(25^{\circ} \mathrm{C} ?\)

Which of the following statements are true for a \(0.10-M\) solution of a weak acid HA? (Choose all that apply.) (a) The pH is 1.00 . (c) \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=\left[\mathrm{A}^{-}\right]\) (b) \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]>>\left[\mathrm{A}^{-}\right]\) (d) The \(\mathrm{pH}\) is less than 1 .

Classify each of the following species as a weak or strong base: (a) \(\mathrm{LiOH},(\mathrm{b}) \mathrm{CN}^{-},(\mathrm{c}) \mathrm{H}_{2} \mathrm{O},(\mathrm{d}) \mathrm{ClO}_{4}^{-},(\mathrm{e}) \mathrm{NH}_{2}^{-}\).

Compare the \(\mathrm{pH}\) values for \(0.10-\mathrm{M}\) solutions of \(\mathrm{NaOH}\) and of \(\mathrm{NH}_{3}\) to illustrate the difference between a strong base and a weak base.

Which of the following has a higher \(\mathrm{pH}\) : (a) \(1.0 \mathrm{M} \mathrm{NH}_{3}\), (b) \(0.20 \mathrm{M} \mathrm{NaOH}\left(K_{\mathrm{b}}\right.\) for \(\left.\mathrm{NH}_{3}=1.8 \times 10^{-5}\right)\) ?