91Ó°ÊÓ

The \(\mathrm{pH}\) of a \(0.30-\mathrm{M}\) solution of a weak base is 10.66 at \(25^{\circ} \mathrm{C}\). What is the \(K_{\mathrm{b}}\) of the base?

What is the original molarity of an aqueous solution of ammonia \(\left(\mathrm{NH}_{3}\right)\) whose \(\mathrm{pH}\) is 11.22 at \(25^{\circ} \mathrm{C}\left(K_{\mathrm{b}}\right.\) for \(\left.\mathrm{NH}_{3}=1.8 \times 10^{-5}\right) ?\)

Calculate the \(\mathrm{pH}\) at \(25^{\circ} \mathrm{C}\) of a \(0.61-M\) aqueous solution of a weak base \(\mathrm{B}\) with a \(K_{\mathrm{b}}\) of \(1.5 \times 10^{-4}\).

Determine the \(K_{\mathrm{b}}\) of a weak base if a \(0.19-M\) aqueous solution of the base at \(25^{\circ} \mathrm{C}\) has a \(\mathrm{pH}\) of 10.88 .

Write the equation relating \(K_{\mathrm{a}}\) for a weak acid and \(K_{\mathrm{b}}\) for its conjugate base. Use \(\mathrm{NH}_{3}\) and its conjugate acid \(\mathrm{NH}_{4}^{+}\) to derive the relationship between \(K_{\mathrm{a}}\) and \(K_{\mathrm{b}}\)

From the relationship \(K_{\mathrm{a}} K_{\mathrm{b}}=K_{\mathrm{w}},\) what can you deduce about the relative strengths of a weak acid and its conjugate base?

Write all the species (except water) that are present in a phosphoric acid solution. Indicate which species can act as a Br?nsted acid, which as a Bronsted base, and which as hoth a Brónsted acid and a Bronsted base.

Explain why it is generally not necessary to take into account second or third ionization constants when calculating the \(\mathrm{pH}\) of a polyprotic acid solution.

Compare the pH of a \(0.040 \mathrm{M} \mathrm{HCl}\) solution with that of a \(0.040 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) solution. (Hint: \(\mathrm{H}_{2} \mathrm{SO}_{4}\) is a strong acid; \(K_{2}\) for \(\mathrm{HSO}_{4}^{-}=1.3 \times 10^{-2}\).)

What are the concentrations of \(\mathrm{HSO}_{4}^{-}, \mathrm{SO}_{4}^{2-}\), and \(\mathrm{H}_{3} \mathrm{O}^{+}\) in a \(0.20 \mathrm{M} \mathrm{KHSO}_{4}\) solution? (Hint: \(\mathrm{H}_{2} \mathrm{SO}_{4}\) is a strong acid; \(K_{\mathrm{a}}\) for \(\mathrm{HSO}_{4}^{-}=1.3 \times 10^{-2}\).)