Chapter 17

What causes heartburn? What are some possible ways to alleviate heartburn?

What is the Arthenius definition of an acid? Of a base?

What is a hydronium ion? Does \(\mathrm{H}^{+}\) exist in solution by itself?

Describe amphoteric behavior and give an example.

What are diprotic and triprotic acids? List an example of each.

Define the acid ionization constant and explain its significance.

Write an equation for the autoionization of water and an expression for the ion product constant for water \(\left(K_{w}\right) .\) What is the value of \(K_{w}\) at \(25^{\circ} \mathrm{C} ?\)

Define pOH. What pOH range is considered acidic? Basic? Neutral? (Assume \(\left.25^{\circ} \mathrm{C} .\right)\)

In most solutions containing a strong or weak acid, the autoionization of water can be neglected when calculating \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right] .\) Explain why this statement is valid.

When calculating \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]\) for weak acid solutions, we can often use the \(x\) is small approximation. Explain the nature of this approximation and why it is valid.

In calculating \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]\) for a mixture of a strong acid and weak acid, the weak acid can often be neglected. Explain why this statement is valid.

Write a generic equation showing how a weak base ionizes water.

How can you determine if an anion will act as a weak base? Write a generic equation showing the reaction by which an anion, \(\mathrm{A}^{-},\) acts as a weak base.

What is the relationship between the acid ionization constant for a weak acid \(\left(K_{\mathrm{a}}\right)\) and the base ionization constant for its conjugate base \(\left(K_{\mathrm{b}}\right) ?\)

For a binary acid, \(\mathrm{H}-\mathrm{Y},\) which factors affect the relative ease with which the acid ionizes?

Which factors affect the relative acidity of an oxyacid?

What is the Lewis definition of an acid? Of a base?

What is a general characteristic of a Lewis acid? Of a Lewis base?

Identify each substance as an acid or a base and write a chemical equation showing how it is an acid or a base according to the Arrhenius definition. a. \(\mathrm{HNO}_{3}(a q)\) b. \(\mathrm{NH}_{4}{\underline{\phantom{xx}}}^{+}(a q)\) c. \(\mathrm{KOH}(a q)\) d. \(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(a q)\)

Identify each substance as an acid or a base and write a chemical equation showing how it is an acid or a base in aqueous solution according to the Arrhenius definition. a. \(\mathrm{NaOH}(a q)\) b. \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)\) c. \(\operatorname{HBr}(a q)\) d. \(\operatorname{Sr}(\mathrm{OH})_{2}(a q)\)

In each reaction, identify the Bronsted-Lowry acid, the BronstedLowry base, the conjugate acid, and the conjugate base. a. \(\mathrm{H}_{2} \mathrm{CO}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{HCO}_{3}^{-}(a q)\) b. \(\mathrm{NH}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(I) \rightleftharpoons \mathrm{NH}_{4}^{+}(a q)+\mathrm{OH}^{-}(a q)\) c. \(\mathrm{HNO}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(I) \longrightarrow \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{NO}_{3}^{-}(a q)\) d. \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{~N}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+}(a q)+\mathrm{OH}^{-}(a q)\)

In each reaction, identify the Bronsted-Lowry acid, the BronstedLowry base, the conjugate acid, and the conjugate base. a. \(\mathrm{HI}(a q)+\mathrm{H}_{2} \mathrm{O}(I) \longrightarrow \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{I}^{-}(a q)\) b. \(\mathrm{CH}_{3} \mathrm{NH}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{CH}_{3} \mathrm{NH}_{3}{\underline{\phantom{xx}}}^{+}(a q)+\mathrm{OH}^{-}(a q)\) c. \(\mathrm{CO}_{3}^{2-}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{HCO}_{3}^{-}(a q)+\mathrm{OH}^{-}(a q)\) d. \(\mathrm{HBr}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{Br}^{-}(a q)\)

Write the formula for the conjugate base of each acid. a.\( HCl\) b. \(\mathrm{H}_{2} \mathrm{SO}_{3}\) c.\( HCHO _{2}\) d. \(HF\)

Write the formula for the conjugate acid of each base. a. \(\mathrm{NH}_{3}\) b. \(\mathrm{ClO}_{4}^{-}\) c. \(\mathrm{HSO}_{4}^{-}\) d. \(\mathrm{CO}_{3}^{2-}\)

Both \(\mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) are amphoteric. Write an equation to show how each substance can act as an acid and another equa- tion to show how each can act as a base.

Both \(\mathrm{HCO}_{3}^{-}\) and \(\mathrm{HS}^{-}\) are amphoteric. Write an equation to show how each substance can act as an acid and another equation to show how each can act as a base.

Calculate \(\left[\mathrm{OH}^{-}\right]\) in each aqueous solution at \(25^{\circ} \mathrm{C}\), and classify the solution as acidic or basic. a. \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=1.2 \times 10^{-8} \mathrm{M}\) b. \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=8.5 \times 10^{-5} \mathrm{M}\) c. \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=3.5 \times 10^{-2} \mathrm{M}\)

Calculate \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]\) in each aqueous solution at \(25^{\circ} \mathrm{C},\) and classify each solution as acidic or basic. a. \(\left[\mathrm{OH}^{-}\right]=1.1 \times 10^{-9} \mathrm{M}\) b. \(\left[\mathrm{OH}^{-}\right]=2.9 \times 10^{-2} \mathrm{M}\) c. \(\left[\mathrm{OH}^{-}\right]=6.9 \times 10^{-12} \mathrm{M}\)

Calculate the \(p \mathrm{H}\) and \(\mathrm{pOH}\) of each solution at \(25^{\circ} \mathrm{C}\). a. \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=1.7 \times 10^{-8} \mathrm{M}\) b. \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=1.0 \times 10^{-7} \mathrm{M}\) c. \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=2.2 \times 10^{-6} \mathrm{M}\)

Calculate \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]\) and \(\left[\mathrm{OH}^{-}\right]\) for each solution at \(25^{\circ} \mathrm{C} .\) a. \(\mathrm{pH}=8.55\) b. \(\mathrm{pH}=11.23\) c. \(\mathrm{pH}=2.87\)

The value of \(K_{w}\) increases with increasing temperature. Is the autoionization of water endothermic or exothermic?

Calculate the \(\mathrm{pH}\) of each acid solution. Explain how the resulting pH values demonstrate that the \(\mathrm{pH}\) of an acid solution should carry as many digits to the right of the decimal place as the number of significant figures in the concentration of the solution. $$ \begin{aligned} \left[\mathrm{H}_{3} \mathrm{O}^{+}\right] &=0.044 \mathrm{M} \\ \left[\mathrm{H}_{3} \mathrm{O}^{+}\right] &=0.045 \mathrm{M} \\ \left[\mathrm{H}_{3} \mathrm{O}^{+}\right] &=0.046 \mathrm{M} \end{aligned} $$

Determine the concentration of \(\mathrm{H}_{3} \mathrm{O}^{+}\) to the correct number of significant figures in a solution with each pH. Describe how these calculations show the relationship between the number of digits to the right of the decimal place in \(\mathrm{pH}\) and the number of significant figures in concentration. \(\mathrm{pH}=2.50\) \(\mathrm{pH}=2.51\) \(\mathrm{pH}=2.52\)

For each strong acid solution, determine \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right],\left[\mathrm{OH}^{-}\right],\) and \(\mathrm{pH} .\) a. \(0.25 \mathrm{MHCl}\) b. \(0.015 \mathrm{MHNO}_{3}\) c. a solution that is \(0.052 \mathrm{M}\) in \(\mathrm{HBr}\) and \(0.020 \mathrm{M}\) in \(\mathrm{HNO}_{3}\) d. a solution that is \(0.655 \% \mathrm{HNO}_{3}\) by mass (assume a density of \(1.01 \mathrm{~g} / \mathrm{mL}\) for the solution \()\)

Determine the \(\mathrm{pH}\) of each solution. a. \(0.048 \mathrm{M} \mathrm{HI}\) b. \(0.0895 \mathrm{M} \mathrm{HClO}_{4}\) c. a solution that is \(0.045 \mathrm{M}\) in \(\mathrm{HClO}_{4}\) and \(0.048 \mathrm{M}\) in \(\mathrm{HCl}\) d. a solution that is \(1.09 \%\) HCl by mass (assume a density of \(1.01 \mathrm{~g} / \mathrm{mL}\) for the solution \()\)

What mass of \(\mathrm{HClO}_{4}\) must be present in \(0.500 \mathrm{~L}\) of solution to obtain a solution with each pH value? a. \(\mathrm{pH}=2.50\) b. \(\mathrm{pH}=1.50\) c. \(\mathrm{pH}=0.50\)

A \(0.185 \mathrm{M}\) solution of a weak acid (HA) has a pH of \(2.95 .\) Calculate the acid ionization constant \(\left(K_{\mathrm{a}}\right)\) for the acid.

A 0.115 M solution of a weak acid (HA) has a pH of 3.29. Calculate the acid ionization constant \(\left(K_{\mathrm{a}}\right)\) for the acid.

A 0.148 M solution of a monoprotic acid has a percent ionization of \(1.55 \% .\) Determine the acid ionization constant \(\left(K_{a}\right)\) for the acid.

A \(0.085 \mathrm{M}\) solution of a monoprotic acid has a percent ionization of \(0.59 \% .\) Determine the acid ionization constant \(\left(K_{\mathrm{a}}\right)\) for the acid.

Find the \(\mathrm{pH}\) and percent ionization of each HF solution. $$ \left(K_{\mathrm{a}} \text { for } \mathrm{HF} \text { is } 6.8 \times 10^{-4} .\right) $$ a. \(0.250 \mathrm{M} \mathrm{HF}\) b. \(0.100 \mathrm{M} \mathrm{HF}\) c. \(0.050 \mathrm{M} \mathrm{HF}\)

Find the \(\mathrm{pH}\) and percent ionization of a \(0.100 \mathrm{M}\) solution of a weak monoprotic acid having the given \(K_{\mathrm{a}}\) values. a. \(K_{\mathrm{a}}=1.0 \times 10^{-5}\) b. \(K_{\mathrm{a}}=1.0 \times 10^{-3}\) c. \(K_{\mathrm{a}}=1.0 \times 10^{-1}\)

Determine the \(\mathrm{pH}\) of a solution that is \(1.55 \%\) NaOH by mass. Assume that the solution has density of \(1.01 \mathrm{~g} / \mathrm{mL}\)

Write equations showing how each weak base ionizes water to form \(\mathrm{OH}^{-}\). Also write the corresponding expression for \(K_{\mathrm{b}}\). a. \(\mathrm{NH}_{3}\) b. \(\mathrm{HCO}_{3}^{-}\) c. \(\mathrm{CH}_{3} \mathrm{NH}_{2}\)

Write equations showing how each weak base ionizes water to form \(\mathrm{OH}^{-}\). Also write the corresponding expression for \(K_{\mathrm{b}}\). a. \(\mathrm{CO}_{3}^{2-}\) b. \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\) c. \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}\)

A 0.135 M solution of a weak base has a pH of 11.23. Determine \(K_{\mathrm{b}}\) for the base.

Determine whether each cation is acidic or pH-neutral. For those cations that are acidic, write an equation that shows how the cation acts as an acid. a. \(\mathrm{NH}_{4}^{+}\) b. \(\mathrm{Na}^{+}\) c. \(\mathrm{Co}^{3+}\) d. \(\mathrm{CH}_{2} \mathrm{NH}_{3}{\underline{\phantom{xx}}}^{+}\)

Determine if each salt will form a solution that is acidic, basic, or \(\mathrm{pH}\) -neutral. a. \(\mathrm{FeCl}_{3}\) b. \(\mathrm{NaF}\) c. \(\mathrm{CaBr}_{2}\) d. \(\mathrm{NH}_{4} \mathrm{Br}\) e. \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{3} \mathrm{NO}_{2}\)

Determine if each salt will form a solution that is acidic, basic, or pH- neutral. a. \(\mathrm{Al}\left(\mathrm{NO}_{3}\right)_{3}\) b. \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{3} \mathrm{NO}_{3}\) c. \(\mathrm{K}_{2} \mathrm{CO}_{3}\) d. \(\mathrm{RbI}\) e. \(\mathrm{NH}_{4} \mathrm{ClO}\)

Write chemical equations and corresponding equilibrium expressions for each of the three ionization steps of phosphoric acid.