Chapter 18

Write balanced equations for the reactions between the following. \begin{equation} \begin{array}{l}{\text { a. aluminum and sulfuric acid }} \\ {\text { b. calcium carbonate and hydrobromic acid }}\end{array} \end{equation}

Challenge The products of an acid-base reaction are \(\mathrm{H}_{3} \mathrm{O}^{+}\) and \(\mathrm{SO}_{4}^{2-}\) . Write a balanced equation for the reaction and identify the conjugate acid-base pairs.

MAIN idea Explain why many Lewis acids and bases are not classified as Arrhenius or Bronsted-Lowry acids and bases.

Explain how the concentrations of hydrogen ions and hydroxide ions determine whether a solution is acidic, basic, or neutral.

Explain why many compounds that contain one or more hydrogen atoms are not classified as Arrhenius acids.

Identify the conjugate acid-base pairs in the following equation. $$\mathrm{HNO}_{2}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{NO}_{2}^{-}+\mathrm{H}_{3} \mathrm{O}^{+}$$

Write the Lewis structure for phosphorus trichloride \(\left(P C_{3}\right) .\) Is \(P C l_{3}\) a Lewis acid, a Lewis base, or neither?

Write ionization equations and acid ionization constant expressions for each acid. \begin{equation} \text { a. HCIO }_{2} \quad\quad\quad\quad \text { b. HNO }_{2} \quad\quad\quad\quad \text { c. HIO } \end{equation}

Write the first and second ionization equations for \(\mathrm{H}_{2} \mathrm{SeO}_{3}\).

Challenge Given the expression \(K_{\mathrm{a}}=\frac{\left[\mathrm{AsO}_{4}^{3-}\right]\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]}{[\mathrm{HCN}]}\) , write the balanced equation for the corresponding reaction.

Write ionization equations and base ionization constant expressions for the following bases. \begin{equation} \begin{array}{ll}{\text { a. hexylamine }\left(\mathrm{C}_{6} \mathrm{H}_{13} \mathrm{NH}_{2}\right)} & {\text { c. carbonate ion }\left(\mathrm{CO}_{3}^{2-}\right)} \\ {\text { b. propylamine }\left(\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{NH}_{2}\right)} & {\text { d. hydrogen sulfite ion }\left(\mathrm{HSO}_{3}^{-}\right)}\end{array} \end{equation}

Challenge Write an equation for a base equilibrium in which the base in the forward reaction is \(\mathrm{PO}_{4}^{3-}\) and the base in the reverse reaction is \(\mathrm{OH}^{-} .\)

Relate the strength of a weak acid to the strength of its conjugate base.

Explain what the \(K_{\mathrm{b}}\) for aniline \(\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\right)\) tells you \(\left(K_{\mathrm{b}}=4.3 \times 10^{-10}\right)\) .

The concentration of either the \(\mathrm{H}^{+}\) ion or the \(\mathrm{OH}^{-}\) ion is given for four aqueous solutions at 298 \(\mathrm{K}\) . For each solution, calculate \(\left[\mathrm{H}^{+}\right]\) or \(\left[\mathrm{OH}^{-}\right] .\) State whether the solution is acidic, basic, or neutral. \begin{equation} \begin{array}{ll}{\text { a. }\left[\mathrm{H}^{+}\right]=1.0 \times 10^{-13} M} & {\text { c. }\left[\mathrm{OH}^{-}\right]=1.0 \times 10^{-3} \mathrm{M}} \\\ {\text { b. }\left[\mathrm{OH}^{-}\right]=1.0 \times 10^{-7} M} & {\text { d. }\left[\mathrm{H}^{+}\right]=4.0 \times 10^{-5} \mathrm{M}}\end{array} \end{equation}

Challenge Calculate the number of \(\mathrm{H}^{+}\) ions and the number of \(\mathrm{OH}^{-}\) ions in 300 \(\mathrm{mL}\) of pure water at 298 \(\mathrm{K} .\)

Calculate the \(\mathrm{pH}\) of solutions having the following ion concentrations at 298 \(\mathrm{K} .\) \begin{equation} \text { a. }\left[\mathrm{H}^{+}\right]=1.0 \times 10^{-2} M \quad \text { b. }\left[\mathrm{H}^{+}\right]=3.0 \times 10^{-6} \mathrm{M} \end{equation}

Calculate the \(\mathrm{pH}\) of aqueous solutions with the following \([\mathrm{H}+]\) at 298 \(\mathrm{K}\). \begin{equation} \text { a. }\left[\mathrm{H}^{+}\right]=0.0055 M \quad \text { b. }\left[\mathrm{H}^{+}\right]=0.000084 \mathrm{M} \end{equation}

Challenge Calculate the \(\mathrm{pH}\) of a solution having \(\left[\mathrm{OH}^{-}\right]=8.2 \times 10^{-6} \mathrm{M}\).

Calculate the \(\mathrm{pH}\) and \(\mathrm{pOH}\) of aqueous solutions with the following concentrations at 298 \(\mathrm{K}\). \begin{equation} \begin{array}{l}{\text { a. }\left[\mathrm{OH}^{-}\right]=1.0 \times 10^{-6} M} \\ {\text { b. }\left[\mathrm{OH}^{-}\right]=6.5 \times 10^{-4} \mathrm{M}} \\ {\text { c. }\left[\mathrm{H}^{+}\right]=3.6 \times 10^{-9} \mathrm{M}} \\ {\text { d. }\left[\mathrm{H}^{+}\right]=2.5 \times 10^{-2} \mathrm{M}}\end{array} \end{equation}

Calculate the \(\mathrm{pH}\) and \(\mathrm{pOH}\) of aqueous solutions with the following concentration at 298 \(\mathrm{K} .\) \begin{equation} \begin{array}{l}{\text { a. }\left[\mathrm{OH}^{-}\right]=0.000033 M} \\\ {\text { b. }\left[\mathrm{H}^{+}\right]=0.0095 M}\end{array} \end{equation}

Challenge Calculate pH and pOH for an aqueous solution containing \(1.0 \times 10^{-3}\) mol of HCl dissolved in 5.0 \(\mathrm{L}\) of solution.

Calculate \(\left[\mathrm{H}^{+}\right]\) and \(\left[\mathrm{OH}^{-}\right]\) in each of the following solutions. \begin{equation} \begin{array}{ll}{\text { a. Milk, } \mathrm{p} \mathrm{H}=6.50 .} & {\text { c. Milk of magnesia, } \mathrm{p} \mathrm{H}=10.50} \\ {\text { b. Lemon juice, } \mathrm{p} \mathrm{H}=2.37} & {\text { d. Household ammonia, } \mathrm{p} \mathrm{H}=11.90}\end{array} \end{equation}

Challenge Calculate the \(\left[\mathrm{H}^{+}\right]\) and \(\left[\mathrm{OH}^{-}\right]\) in a sample of seawater with a pOH \(=5.60 .\)

Calculate the \(K_{\mathrm{a}}\) for the following acids using the given information. \begin{equation} \text { a. }0.220 M \text { solution of } \mathrm{H}_{3} \mathrm{AsO}_{4}, \mathrm{pH}=1.50 \quad \text { b. } 0.0400 M \text { solution of } \mathrm{HClO}_{2}, \mathrm{pH}=1.80 \end{equation}

Calculate the \(K_{\mathrm{a}}\) of the following acids using the given information. \begin{equation} \begin{array}{l}{\text { a. } 0.00330 M \text { solution of benzoic acid }\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}\right), \mathrm{pOH}=10.70} \\\ {\text { b. } 0.100 M \text { solution of cyanic acid }(\mathrm{HCNO}), \mathrm{pOH}=11.00} \\ {\text { c. } 0.150 \mathrm{M} \text { solution of butanoic acid }\left(\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{COOH}\right), \mathrm{pOH}=11.18}\end{array} \end{equation}

MAIN Idea Explain why the pH of an acidic solution is always a smaller number than the pOH of the same solution.

Describe how you can determine the pH of a solution if you know its pOH.

Explain the significance of \(K_{w}\) in aqueous solutions.

Explain, using Le Chatelier's principle, what happens to the \([\mathrm{H}+]\) of a 0.10 M solution of acetic acid when a drop of NaOH solution is added.

Calculate The pH of a tomato is approximately \(4.50 .\) What are \(\left[H^{+}\right]\) and \(\left[0 \mathrm{H}^{-}\right]\) in a tomato?

Calculate the \(\mathrm{pH}\) of the following solutions. \begin{equation} \begin{array}{ll}{\text { a. } 1.0 M \mathrm{Hl}} & {\text { c. } 1.0 M \mathrm{KOH}} \\ {\text { b. } 0.050 M \mathrm{HNO}_{3}} & {\text { d. } 2.4 \times 10^{-5} M \mathrm{Mg}(\mathrm{OH})_{2}}\end{array} \end{equation}

What is the molarity of a nitric acid solution if 43.33 \(\mathrm{mL}\) of 0.1000\(M\) \(\mathrm{KOH}\) solution is needed to neutralize 20.00 \(\mathrm{mL}\) of the acid solution?

What is the concentration of a household ammonia cleaning solution if 49.90 \(\mathrm{mL}\) of 0.5900 \(M\) \(\mathrm{HCl}\) is required to neutralize 25.00 \(\mathrm{mL}\) of the solution?

Challenge How many milliliters of 0.500 \(\mathrm{M}\) NaOH would neutralize 25.00 \(\mathrm{mL}\) of 0.100 \(M\) \(\mathrm{H}_{3} \mathrm{PO}_{4} ?\)

Write equations for the salt hydrolysis reactions occuring when the following salts dissolve in water. Classify each as acidic, basic, or neutral. \begin{equation} \begin{array}{l}{\text { a. ammonium nitrate } \quad \text { c. rubidium acetate }} \\ {\text { b. potassium sulfate}} \quad\quad {\text {d. calcium carbonate }}\end{array} \end{equation}

Challenge Write the equation for the reaction that occurs in a titration of ammonium hydroxide \(\left(\mathrm{NH}_{4} \mathrm{OH}\right]\) with hydrogen bromide \((\mathrm{HBr}) .\) Will the \(\mathrm{pH}\) at the equivalence point be greater or less than 7 ?

Explain the difference between the equivalence point and the end point of a titration.

Compare the results of two experiments: First, a small amount of base is added to an unbuffered solution with a pH of \(7 .\) Second, the same amount of base is added to a buffered solution with a pH of \(7 .\)

Calculate the molarity of a solution of hydrobromic acid (HBr) if 30.35 \(\mathrm{mL}\) of 0.1000 \(\mathrm{M} \mathrm{NaOH}\) is required to titrate 25.00 \(\mathrm{mL}\) of the acid to the equivalence point.

Design an Experiment Describe how you would design and perform a titration in which you use 0.250\(M \mathrm{HNO}_{3}\) to determine the molarity of a cesium hydroxide solution. Include the formula and net ionic equations.

In terms of ion concentrations, distinguish between acidic, neutral, and basic solutions.

Write a balanced chemical equation that represents the self-ionization of water.

Classify each compound as an Arrhenius acid or an Arrhenius base. \begin{equation} \begin{array}{ll}{\text { a. } \mathrm{H}_{2} \mathrm{S}} & {\text { c. } \mathrm{Mg}(\mathrm{OH})_{2}} \\ {\text { b. } \mathrm{RbOH}} & {\text { d. } \mathrm{H}_{3} \mathrm{PO}_{4}}\end{array} \end{equation}

Geology When a geologist adds a few drops of HCl to a rock, gas bubbles form. What might the geologist conclude about the nature of the gas and the rock?

Explain the difference between a monoprotic acid, a diprotic acid, and a triprotic acid. Give an example of each.

Why can \(\mathrm{H}^{+}\) and \(\mathrm{H}_{3} \mathrm{O}^{+}\) be used interchangeably in chemical equations?

Use the symbols \(<,>,\) and \(=\) to express the relationship between the concentrations of \(\mathrm{H}^{+}\) ions and \(\mathrm{OH}^{-}\) ions in acidic, neutral, and basic solutions.

Explain how the definition of a Lewis acid differs from the definition of a Bronsted-Lowry acid.

Write a balanced chemical equation for each of the following. \begin{equation} \begin{array}{l}{\text { a. the dissociation of solid magnesium hydroxide in }} \\ {\text { water }} \\ {\text { b. the reaction of magnesium metal and hydrobromic }} \\ {\text { acid }} \\ {\text { c. the ionization of propanoic acid (CH_ }_{3} \mathrm{CH}_{2} \mathrm{COOH} )} \\ {\text { in water }} \\ {\text { d. the second ionization of sulfuric acid in water }}\end{array} \end{equation}