Problem 70
A solution is prepared by dissolving 0.56 g benzoic acid \(\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}, K_{\mathrm{a}}=6.4 \times 10^{-5}\right)\) in enough water to make 1.0 \(\mathrm{L}\) of solution. Calculate \(\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}\right],\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2}\right],\left[\mathrm{H}^{+}\right]\) \(\left[\mathrm{OH}^{-}\right],\) and the pH of this solution.
Problem 71
A typical aspirin tablet contains 325 mg acetylsalicylic acid \(\left(\mathrm{HC}_{9} \mathrm{H}_{7} \mathrm{O}_{4}\right) .\) Calculate the \(\mathrm{pH}\) of a solution that is prepared by dissolving two aspirin tablets in enough water to make one \(\operatorname{cup}(237 \mathrm{mL})\) of solution. Assume the aspirin tablets are pure acetylsalicylic acid, \(K_{\mathrm{a}}=3.3 \times 10^{-4}\) .
Problem 72
Saccharin, a sugar substitute, has the formula \(\mathrm{HC}_{7} \mathrm{H}_{4} \mathrm{NSO}_{3}\) and is a weak acid with \(K_{\mathrm{a}}=2.0 \times 10^{-12} .\) If 100.0 \(\mathrm{g}\) of saccharin is dissolved in enough water to make 340 \(\mathrm{mL}\) of solution, calculate the \(\mathrm{pH}\) of the resulting solution.
Problem 74
A solution contains a mixture of acids: 0.50\(M\) HA \(\left(K_{\mathrm{a}}=1.0\right.\) \(\times 10^{-3} ), 0.20 M \mathrm{HB}\left(K_{\mathrm{a}}=1.0 \times 10^{-10}\right),\) and 0.10 \(\mathrm{MHC}\left(K_{\mathrm{a}}=\right.\) \(1.0 \times 10^{-12} ) .\) Calculate the \(\left[\mathrm{H}^{+}\right]\) in this solution.
Problem 75
Calculate the percent dissociation of the acid in each of the following solutions. a. 0.50\(M\) acetic acid b. 0.050\(M\) acetic acid c. 0.0050\(M\) acetic acid d. Use Le Châtelier's principle to explain why percent dissociation increases as the concentration of a weak acid decreases. e. Even though the percent dissociation increases from solutions a to \(c,\) the \(\left[\mathrm{H}^{+}\right]\) decreases. Explain.
Problem 76
Calculate the percent dissociation for a \(0.22-M\) solution of chlorous acid \(\left(\mathrm{HClO}_{2}, K_{\mathrm{a}}=0.012\right)\)
Problem 77
A \(0.15-M\) solution of a weak acid is 3.0\(\%\) dissociated. Calculate \(K_{\mathrm{a}}\) .
Problem 78
A \(1.0 \times 10^{-2}-M\) solution of cyanic acid (HOCN) is 17\(\%\) dissociated. Calculate \(K_{\mathrm{a}}\) for cyanic acid.
Problem 79
Trichloroacetic acid \(\left(\mathrm{CCl}_{3} \mathrm{CO}_{2} \mathrm{H}\right)\) is a corrosive acid that is used to precipitate proteins. The pH of a \(0.050-M\) solution of trichloroacetic acid is the same as the pH of a \(0.040-M \mathrm{HClO}_{4}\) solution. Calculate \(K_{\mathrm{a}}\) for trichloroacetic acid.
Problem 80
The pH of a \(0.063-M\) solution of hypobromous acid (HOBr but usually written \(\mathrm{HBrO}\) ) is \(4.95 .\) Calculate \(K_{\mathrm{a}} .\)
