Problem 81
Decide whether each of the following substances should be classified as a Lewis acid or a Lewis base. (a) \(\mathrm{H}_{2} \mathrm{NOH}\) in the reaction \(\mathrm{H}_{2} \mathrm{NOH}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \longrightarrow\left[\mathrm{H}_{3} \mathrm{NOH}\right] \mathrm{Cl}(\mathrm{aq})\) (b) \(\mathrm{Fe}^{2+}\) (c) \(\mathrm{CH}_{3} \mathrm{NH}_{2}\) (Hint: Draw the electron dot structure.
Problem 82
Decide whether each of the following substances should be classified as a Lewis acid or a Lewis base. (a) \(\mathrm{BCl}_{3}\) (Hint: Draw the electron dot structure.) (b) \(\mathrm{H}_{2} \mathrm{NNH}_{2},\) hydrazine (Hint: Draw the electron dot structure. (c) the reactants in the reaction \(\mathrm{Ag}^{+}(\mathrm{aq})+2 \mathrm{NH}_{3}(\mathrm{aq}) \rightleftharpoons\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right]^{+}(\mathrm{aq})\)
Problem 84
Trimethylamine, \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N},\) is a common reagent. It interacts readily with diborane gas, \(\mathrm{B}_{2} \mathrm{H}_{6}\). The latter dissociates to \(\mathrm{BH}_{3}\), and this forms a complex with the amine, \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N} \rightarrow \mathrm{BH}_{3} .\) Is the \(\mathrm{BH}_{3}\) fragment a Lewis acid or a Lewis base?
Problem 85
About this time, you may be wishing you had an aspirin. Aspirin is an organic acid with a \(K_{\mathrm{a}}\) of \(3.27 \times 10^{-4}\) for the reaction $$\mathrm{HC}_{3} \mathrm{H}_{7} \mathrm{O}_{4}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\ell) \rightleftharpoons_{\mathrm{C}_{9} \mathrm{H}_{7} \mathrm{O}_{4}^{-}(\mathrm{aq})}+\mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq})$$ If you have two tablets, each containing 0.325 g of aspirin (mixed with a neutral "binder" to hold the tablet together), and you dissolve them in a glass of water to give \(225 \mathrm{mL}\) of solution, what is the pH of the solution?
Problem 87
A 2.50 -g sample of a solid that could be \(\mathrm{Ba}(\mathrm{OH})_{2}\) or \(\operatorname{Sr}(\mathrm{OH})_{2}\) was dissolved in enough water to make 1.00 L of solution. If the pH of the solution is \(12.61,\) what is the identity of the solid?
Problem 90
For each of the following reactions, predict whether the equilibrium lies predominantly to the left or to the right. Explain your prediction briefly. (a) \(\mathrm{HCO}_{3}^{-}(\mathrm{aq})+\mathrm{SO}_{4}^{2-}(\mathrm{aq}) \rightleftarrows\) \(\mathrm{CO}_{3}^{2-}(\mathrm{aq})+\mathrm{HSO}_{4}^{-}(\mathrm{aq})\) (b) \(\mathrm{HSO}_{4}^{-}(\mathrm{aq})+\mathrm{CH}_{3} \mathrm{CO}_{2}^{-}(\mathrm{aq}) \rightleftarrows\) \(\mathrm{SO}_{4}^{2-}(\mathrm{aq})+\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(\mathrm{aq})\) (c) \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}(\mathrm{aq})+\mathrm{CH}_{3} \mathrm{CO}_{2}^{-}(\mathrm{aq}) \rightleftarrows\) \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5}(\mathrm{OH})\right]^{+}(\mathrm{aq})+\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(\mathrm{aq})\)
Problem 91
A monoprotic acid HX has \(K_{a}=1.3 \times 10^{-3} .\) Calculate the equilibrium concentrations of HX and \(\mathrm{H}_{3} \mathrm{O}^{+}\) and the \(\mathrm{pH}\) for a \(0.010 \mathrm{M}\) solution of the acid.
Problem 92
Arrange the following \(0.10 \mathrm{M}\) solutions in order of increasing pH. (a) \(\mathrm{NaCl}\) (b) \(\mathrm{NH}_{4} \mathrm{Cl}\) (c) HCl (d) \(\mathrm{NaCH}_{3} \mathrm{CO}_{2}\) (e) KOH
Problem 93
\(m\) -Nitrophenol, a weak acid, can be used as a pH indicator because it is yellow at a pH above 8.6 and colorless at a pH below 6.8. If the pH of a 0.010 M solution of the compound is \(3.44,\) calculate its \(\mathrm{p} K_{\mathrm{a}}\).
Problem 95
The local anesthetic novocaine is the hydrogen chloride salt of an organic base, procaine. $$\begin{array}{cc} \mathrm{C}_{13} \mathrm{H}_{20} \mathrm{N}_{2} \mathrm{O}_{2}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \longrightarrow & \left.\mathrm{IHC}_{13} \mathrm{H}_{20} \mathrm{N}_{2} \mathrm{O}_{2}\right]^{+} \mathrm{Cl}^{-}(\mathrm{aq}) \\ \text { procaine } & \text { novocaine } \end{array}$$ The \(\mathrm{p} K_{\mathrm{a}}\) for novocaine is \(8.85 .\) What is the \(\mathrm{pH}\) of a \(0.0015 \mathrm{M}\) solution of novocaine?
