Problem 47
What does the ionization constant tell us about the strength of an acid?
Problem 48
List the factors on which the \(K_{\mathrm{a}}\) of a weak acid depends.
Problem 49
Why do we normally not quote \(K_{\mathrm{a}}\) values for strong acids such as \(\mathrm{HCl}\) and \(\mathrm{HNO}_{3}\) ? Why is it necessary to specify temperature when giving \(K_{a}\) values?
Problem 50
Which of the following solutions has the highest \(\mathrm{pH}\) : (a) \(0.40 \mathrm{M} \mathrm{HCOOH}\) (b) \(0.40 \mathrm{M} \mathrm{HClO}_{4}\) (c) \(0.40 \mathrm{M}\) \(\mathrm{CH}_{3} \mathrm{COOH} ?\)
Problem 51
Without referring to the text, write the formulas of four weak acids.
Problem 52
In biological and medical applications, it is often necessary to study the autoionization of water at \(37^{\circ} \mathrm{C}\) instead of \(25^{\circ} \mathrm{C}\). Given that \(K_{\mathrm{w}}\) for water is \(2.5 \times 10^{-14}\) at \(37^{\circ} \mathrm{C},\) calculate the \(\mathrm{pH}\) of pure water at this temperature.
Problem 53
The \(K_{\mathrm{a}}\) for benzoic acid is \(6.5 \times 10^{-5} .\) Calculate the \(\mathrm{pH}\) of a \(0.10-M\) aqueous solution of benzoic acid at \(25^{\circ} \mathrm{C}\).
Problem 54
The \(K_{\mathrm{a}}\) for hydrofluoric acid is \(7.1 \times 10^{-4}\). Calculate the \(\mathrm{pH}\) of a \(0.15-M\) aqueous solution of hydrofluoric acid at \(25^{\circ} \mathrm{C}\).
Problem 55
Calculate the \(\mathrm{pH}\) of an aqueous solution at \(25^{\circ} \mathrm{C}\) that is \(0.095 M\) in hydrocyanic acid \((\mathrm{HCN}) .\left(K_{\mathrm{a}}\right.\) for hydrocyanic acid \(\left.=4.9 \times 10^{-10} .\right)\)
Problem 56
Calculate the \(\mathrm{pH}\) of an aqueous solution at \(25^{\circ} \mathrm{C}\) that is \(0.34 \mathrm{M}\) in phenol \(\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}\right) .\left(K_{\mathrm{a}}\right.\) for phenol \(=1.3 \times 10^{-10}\).)
