Write the chemical equation and the \(K_{b}\) expression for the reaction of each of the following bases with water: (a) trimethylamine, \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N} ;\) (b) sulfite, \(\mathrm{SO}_{3}^{2-}\); (c) cyanide, \(\mathrm{CN}^{-}\).

Short Answer

Expert verified
The chemical equations and \(K_b\) expressions for the given bases reacting with water are: (a) Trimethylamine (\(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}\)): $$\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N} + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \left(\mathrm{CH}_{3}\right)_{3} \mathrm{~NH}^+ + \mathrm{OH}^-$$ $$K_{b1} = \frac{[\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~NH}^+][\mathrm{OH}^-]}{[\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}]}$$ (b) Sulfite (\(\mathrm{SO}_{3}^{2-}\)): $$\mathrm{SO}_{3}^{2-} + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \mathrm{HSO}_{3}^- + \mathrm{OH}^-$$ $$K_{b2} = \frac{[\mathrm{HSO}_{3}^-][\mathrm{OH}^-]}{[\mathrm{SO}_{3}^{2-}]}$$ (c) Cyanide (\(\mathrm{CN}^{-}\)): $$\mathrm{CN}^- + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \mathrm{HCN} + \mathrm{OH}^-$$ $$K_{b3} = \frac{[\mathrm{HCN}][\mathrm{OH}^-]}{[\mathrm{CN}^-]}$$

Step by step solution

01

(a) Trimethylamine with water

Let's write the chemical equation for the reaction of trimethylamine, \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}\), with water, \(\mathrm{H}_2\mathrm{O}\). 1. Reaction with water: \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N} + \mathrm{H}_{2}\mathrm{O}\) 2. Balanced chemical equation: The trimethylamine reacts with water to form its conjugate acid, \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~NH}^+\), and hydroxide ions, \(\mathrm{OH}^-\). $$\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N} + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \left(\mathrm{CH}_{3}\right)_{3} \mathrm{~NH}^+ + \mathrm{OH}^-$$ 3. \(K_b\) expression: let the \(K_b\) for the reaction be represented by \(K_{b1}\). The \(K_b\) expression is given as the product of ion concentrations divided by the concentration of the base: $$K_{b1} = \frac{[\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~NH}^+][\mathrm{OH}^-]}{[\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}]}$$
02

(b) Sulfite with water

Now, let's write the chemical equation for the reaction of sulfite, \(\mathrm{SO}_{3}^{2-}\), with water, \(\mathrm{H}_2\mathrm{O}\). 1. Reaction with water: \(\mathrm{SO}_{3}^{2-} + \mathrm{H}_{2}\mathrm{O}\) 2. Balanced chemical equation: The sulfite reacts with water to form bisulfite ions, \(\mathrm{HSO}_{3}^-\), and hydroxide ions, \(\mathrm{OH}^-\). $$\mathrm{SO}_{3}^{2-} + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \mathrm{HSO}_{3}^- + \mathrm{OH}^-$$ 3. \(K_b\) expression: let the \(K_b\) for the reaction be represented by \(K_{b2}\). The \(K_b\) expression is given as the product of ion concentrations divided by the concentration of the base: $$K_{b2} = \frac{[\mathrm{HSO}_{3}^-][\mathrm{OH}^-]}{[\mathrm{SO}_{3}^{2-}]}$$
03

(c) Cyanide with water

Finally, let's write the chemical equation for the reaction of cyanide, \(\mathrm{CN}^{-}\), with water, \(\mathrm{H}_2\mathrm{O}\). 1. Reaction with water: \(\mathrm{CN}^{-} + \mathrm{H}_{2}\mathrm{O}\) 2. Balanced chemical equation: The cyanide reacts with water to form hydrogen cyanide, \(\mathrm{HCN}\), and hydroxide ions, \(\mathrm{OH}^-\). $$\mathrm{CN}^- + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \mathrm{HCN} + \mathrm{OH}^-$$ 3. \(K_b\) expression: let the \(K_b\) for the reaction be represented by \(K_{b3}\). The \(K_b\) expression is given as the product of ion concentrations divided by the concentration of the base: $$K_{b3} = \frac{[\mathrm{HCN}][\mathrm{OH}^-]}{[\mathrm{CN}^-]}$$

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Most popular questions from this chapter

Calculate the percent ionization of hydrazoic acid \(\left(\mathrm{HN}_{3}\right)\) in solutions of each of the following concentrations \(\left(K_{a}\right.\) is (c) \(0.0400 \mathrm{M}\). given in Appendix $\mathrm{D}):(\mathbf{a}) 0.400 \mathrm{M},(\mathbf{b}) 0.100 \mathrm{M}$

Calculate the pH of each of the following solutions \(\left(K_{a}\right.\) and \(K_{b}\) values are given in Appendix D): (a) \(0.150 \mathrm{M}\) propionic acid $\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{COOH}\right)$ (b) \(0.250 \mathrm{M}\) hydrogen chromate ion \(\left(\mathrm{HCrO}_{4}^{-}\right),(\mathbf{c}) 0.750 \mathrm{M}\) pyridine \(\left(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{~N}\right)\)

(a) Using dissociation constants from Appendix D, determine the value for the equilibrium constant for each of the following reactions. (i) $\mathrm{HCO}_{3}^{-}(a q)+\mathrm{OH}^{-}(a q) \rightleftharpoons \mathrm{CO}_{3}^{2-}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$ (ii) $\mathrm{NH}_{4}^{+}(a q)+\mathrm{CO}_{3}^{2-}(a q) \rightleftharpoons \mathrm{NH}_{3}(a q)+\mathrm{HCO}_{3}^{-}(a q)$ (b) We usually use single arrows for reactions when the forward reaction is appreciable ( \(K\) much greater than 1) or when products escape from the system, so that equilibrium is never established. If we follow this convention, which of these equilibria might be written with a single arrow?

For each of these reactions, identify the acid and base among the reactants, and state if the acids and bases are Lewis, Arrhenius, and/or Brønsted-Lowry: (a) \(\mathrm{PCl}_{4}^{+}+\mathrm{Cl}^{-} \longrightarrow \mathrm{PCl}_{5}\) (b) $\mathrm{NH}_{3}+\mathrm{BF}_{3} \longrightarrow \mathrm{H}_{3} \mathrm{NBF}_{3}$ (c) $\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}+\mathrm{H}_{2} \mathrm{O} \longrightarrow\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{OH}\right]^{2+}+\mathrm{H}_{3} \mathrm{O}^{+}$

Calculate \(\left[\mathrm{OH}^{-}\right]\) and \(\mathrm{pH}\) for each of the following strong base solutions: (a) \(0.182 \mathrm{M} \mathrm{KOH},\) (b) \(3.165 \mathrm{~g}\) of \(\mathrm{KOH}\) in 500.0 \(\mathrm{mL}\) of solution, \((\mathbf{c}) 10.0 \mathrm{~mL}\) of $0.0105 \mathrm{M} \mathrm{Ca}(\mathrm{OH})_{2}\( diluted to \)500.0 \mathrm{~mL},(\mathbf{d})\( a solution formed by mixing \)20.0 \mathrm{~mL}$ of 0.015 \(M \mathrm{Ba}(\mathrm{OH})_{2}\) with \(40.0 \mathrm{~mL}\) of $8.2 \times 10^{-3} \mathrm{M} \mathrm{NaOH}$.

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