# Chemistry

## Educators

Problem 1

Write equations that show $\mathrm{NH}_{3}$ as both a conjugate acid and a conjugate base.

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Problem 2

Write equations that show $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$ acting both as an acid and as a base.

Problem 3

Show by suitable net ionic equations that each of the following species can act as a Bransted-Lowry acid:
$$\begin{array}{l}{\text { (a) } \mathrm{H}_{3} \mathrm{O}^{+}} \\ {\text { (b) } \mathrm{HCl}} \\ {\text { (c) } \mathrm{NH}_{3}} \\ {\text { (d) } \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}} \\ {\text { (e) } \mathrm{NH}_{4}^{+}} \\ {\text { (f) } \mathrm{HSO}_{4}^{-}}\end{array}$$

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Problem 4

Show by suitable net ionic equations that each of the following species can act as a Bronsted-Lowry acid:
$$\begin{array}{l}{\text { (a) } \mathrm{HNO}_{3}} \\ {\text { (b) } \mathrm{PH}_{4}^{+}} \\ {\text { (c) } \mathrm{H}_{2} \mathrm{S}} \\ {\text { (d) } \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH}} \\ {\text { (e) } \mathrm{H}_{2} \mathrm{PO}_{4}^{-}} \\ {\text { (f) } \mathrm{HS}^{-}}\end{array}$$

Problem 5

Show by suitable net ionic equations that each of the following species can act as a Bronsted-Lowry base:
$$\begin{array}{l}{\text { (a) } \mathrm{H}_{2} \mathrm{O}} \\ {\text { (b) } \mathrm{OH}^{-}} \\ {\text { (c) } \mathrm{NH}_{3}} \\ {\text { (d) } \mathrm{CN}^{-}} \\ {\text { (e) } \mathrm{S}^{2-}} \\ {\text { (f) } \mathrm{H}_{2} \mathrm{PO}_{4}^{-}}\end{array}$$

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Problem 6

Show by suitable net ionic equations that each of the following species can act as a Bronsted-Lowry base:
$$\begin{array}{l}{\text { (a) } \mathrm{HS}^{-}} \\ {\text { (b) } \mathrm{PO}_{4}^{3-}} \\ {\text { (c) } \mathrm{NH}_{2}^{-}} \\ {\text { (d) } \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}} \\ {\text { (e) } \mathrm{O}^{2-}} \\ {\text { (f) } \mathrm{H}_{2} \mathrm{PO}_{4}^{-}}\end{array}$$

Problem 7

What is the conjugate acid of each of the following? What is the conjugate base of each?
$$\begin{array}{l}{\text { (a) } \mathrm{OH}^{-}} \\ {\text { (b) } \mathrm{H}_{2} \mathrm{O}} \\ {\text { (c) } \mathrm{HCO}_{3}^{-}} \\ {\text { (d) } \mathrm{NH}_{3}} \\ {\text { (e) } \mathrm{HSO}_{4}-} \\ {\text { (f) } \mathrm{H}_{2} \mathrm{O}_{2}} \\ {\text { (g) } \mathrm{HS}^{-}} \\ {\text { (h) } \mathrm{H}_{5} \mathrm{N}_{2}^{+}}\end{array}$$

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Problem 8

What is the conjugate acid of each of the following? What is the conjugate base of each?
$$\begin{array}{l}{\text { (a) } \mathrm{H}_{2} \mathrm{S}} \\ {\text { (b) } \mathrm{H}_{2} \mathrm{PO}_{4}^{-}} \\ {\text { (c) } \mathrm{PH}_{3}} \\ {\text { (d) } \mathrm{HS}^{-}} \\ {\text { (e) } \mathrm{HSO}_{3}^{-}} \\ {\text { (f) } \mathrm{H}_{3} \mathrm{O}_{2}^{+}} \\ {\text { (g) } \mathrm{H}_{4} \mathrm{N}_{2}} \\ {\text { (h) } \mathrm{CH}_{3} \mathrm{OH}}\end{array}$$

Problem 9

Identify and label the Bronsted-Lowry acid, its conjugate base, the Bronsted-Lowry base, and its conjugate acid in each of the following equations:
$$\begin{array}{l}{\text { (a) } \mathrm{HNO}_{3}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{NO}_{3}^{-}} \\ {\text { (b) } \mathrm{CN}^{-}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{HCN}+\mathrm{OH}^{-}} \\ {\text { (c) } \mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{Cl}^{-} \longrightarrow \mathrm{HCl}+\mathrm{HSO}_{4}^{-}} \\ {\text { (d) } \mathrm{HSO}_{4}^{-}+\mathrm{OH}^{-} \longrightarrow \mathrm{SO}_{4}^{2-}+\mathrm{H}_{2} \mathrm{O}} \\ {\text { (e) } \mathrm{O}^{2-}+\mathrm{H}_{2} \mathrm{O} \longrightarrow 2 \mathrm{OH}^{-}} \\ {\text { (f) }\left[\mathrm{Cu}\left(\mathrm{H}_{2} \mathrm{O}\right)_{3}(\mathrm{OH})\right]^{+}+\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+} \longrightarrow\left[\mathrm{Cu}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}\right]^{2+}+\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5}(\mathrm{OH})\right]^{2+}} \\ {\text { (g) } \mathrm{H}_{2} \mathrm{S}+\mathrm{NH}_{2}^{-} \rightarrow \mathrm{HS}^{-}+\mathrm{NH}_{3}}\end{array}$$

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Problem 10

Identify and label the Bronsted-Lowry acid, its conjugate base, the Brensted-Lowry base, and its conjugate acid in each of the following equations:
$$\begin{array}{l}{\text { (a) } \mathrm{NO}_{2}^{-}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{HNO}_{2}+\mathrm{OH}^{-}} \\ {\text { (b) } \mathrm{HBr}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{Br}^{-}} \\ {\text { (c) } \mathrm{HS}^{-}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{H}_{2} \mathrm{S}+\mathrm{OH}^{-}} \\ {\text { (d) } \mathrm{H}_{2} \mathrm{PO}_{4}^{-}+\mathrm{OH}^{-} \longrightarrow \mathrm{HPO}_{4}^{2-}+\mathrm{H}_{2} \mathrm{O}} \\ {\text { (e) } \mathrm{H}_{2} \mathrm{PO}_{4}^{-}+\mathrm{HCl} \longrightarrow \mathrm{H}_{3} \mathrm{PO}_{4}+\mathrm{Cl}^{-}} \\ {\text { (f) }\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5}(\mathrm{OH})\right]^{2+}+\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+} \longrightarrow\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}+\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5}(\mathrm{OH})\right]^{2+}} \\ {\text { (g) } \mathrm{CH}_{3} \mathrm{OH}+\mathrm{H}^{-} \longrightarrow \mathrm{CH}_{3} \mathrm{O}^{-}+\mathrm{H}_{2}}\end{array}$$

Problem 11

What are amphiprotic species? Mlustrate with suitable equations.

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Problem 12

State which of the following species are amphiprotic and write chemical equations illustrating the amphiprotic character of these species:
$$\begin{array}{l}{\text { (a) } \mathrm{H}_{2} \mathrm{O}} \\ {\text { (b) } \mathrm{H}_{2} \mathrm{PO}_{4}^{-}} \\ {\text { (c) } \mathrm{S}^{2-}} \\ {\text { (d) } \mathrm{CO}_{3}^{2-}} \\ {\text { (e) } \mathrm{HSO}_{4}^{-}}\end{array}$$

Problem 13

State which of the following species are amphiprotic and write chemical equations illustrating the amphiprotic character of these species.
$$\begin{array}{l}{\text { (a) } \mathrm{NH}_{3}} \\ {\text { (b) } \mathrm{HPO}_{4}-} \\ {\text { (c) } \mathrm{Br}^{-}}\end{array}$$
$$\begin{array}{l}{\text { (d) } \mathrm{NH}_{4}^{+}} \\ {\text { (e) } \mathrm{ASO}_{4}^{3-}}\end{array}$$

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Problem 14

Is the self ionization of water endothermic or exonization constant for water $\left(K_{\mathrm{w}}\right)$ is $2.9 \times$ $10^{-14}$ at $40^{\circ} \mathrm{C}$ and $9.3 \times 10^{-14} \mathrm{at} 60^{\circ} \mathrm{C} .$

Problem 15

Explain why a sample of pure water at $40^{\circ} \mathrm{C}$ is neutral even though $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=1.7 \times 10^{-7} \mathrm{M} . K_{\mathrm{w}}$ is $2.9 \times$ $10^{-14} \mathrm{at}$ at $40^{\circ} \mathrm{C} .$

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Problem 16

The ionization constant for water $\left(K_{\mathrm{w}}\right)$ is $2.9 \times 10^{-14} \mathrm{at} 40^{\circ} \mathrm{C} .$ Calculate $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right],\left[\mathrm{OH}^{-}\right], \mathrm{pH}$ , and poH for
pure water at $40^{\circ} \mathrm{C} .$

Problem 17

The ionization constant for water $\left(K_{\mathrm{w}}\right)$ is $9.311 \times 10^{-14}$ at $60^{\circ} \mathrm{C} .$ Calculate $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right],\left[\mathrm{OH}^{-}\right], \mathrm{pH},$ and pOH for pure water at $60^{\circ} \mathrm{C}$

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Problem 18

Calculate the pH and the pOH of each of the following solutions at $25^{\circ} \mathrm{C}$ for which the substances ionize completely:
$$\begin{array}{l}{\text { (a) } 0.200 \mathrm{M} \mathrm{Cl}} \\ {\text { (b) } 0.0143 \mathrm{M} \mathrm{NaOH}} \\ {\text { (c) } 3.0 \mathrm{M} \mathrm{HNO}_{3}} \\ {\text { (d) } 0.0031 \mathrm{M} \mathrm{Ca}(\mathrm{OH})_{2}}\end{array}$$

Problem 19

Calculate the pH and the pOH of each of the following solutions at $25^{\circ} \mathrm{C}$ for which the substances ionize completely:
$$\begin{array}{l}{\text { (a) } 0.000259 \mathrm{M} \mathrm{HClO}_{4}} \\ {\text { (b) } 0.21 \mathrm{M} \mathrm{NaOH}} \\ {\text { (c) } 0.000071 \mathrm{M} \mathrm{Ba}(\mathrm{OH})_{2}} \\ {\text { (d) } 2.5 \mathrm{M} \mathrm{KOH}}\end{array}$$

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Problem 20

What are the pH and pOH of a solution of 2.0 $\mathrm{M}$ HCl, which ionizes completely?

Problem 21

What are the hydronium and hydroxide ion concentrations in a solution whose pH is 6.52$?$

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Problem 22

Calculate the hydrogen ion concentration and the hydroxide ion concentration in wine from its pH. See Figure 14.2 for useful information.

Problem 23

Calculate the hydronium ion concentration and the hydroxide ion concentration in lime juice from its pH. See Figure 14.2 for useful information.

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Problem 24

The hydronium ion concentration in a sample of rainwater is found to be $1.7 \times 10^{-6} \mathrm{M}$ at $25^{\circ} \mathrm{C}$ . What is the concentration of hydroxide ins in the rainwater?

Problem 25

The hydroxide ion concentration in household ammonia is $3.2 \times 10^{-3} \mathrm{M}$ at $25^{\circ} \mathrm{C}$ . What is the concentration of hydronium ions in the solution?

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Problem 26

Explain why the neutralization of a strong acid and a weak base gives a weakly aciduic solution.

Problem 27

Explain why the neutralization reaction of a weak acid and a strong base gives a weakly basic solution.

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Problem 28

Use this list of important industrial compounds (and Figure 14.8$)$ to answer the following questions regarding: $\mathrm{CaO}, \mathrm{Ca}(\mathrm{OH})_{2}, \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}, \mathrm{CO}_{2}$ $\mathrm{HCl}, \mathrm{H}_{2} \mathrm{CO}_{3}, \mathrm{HF}, \mathrm{HNO}_{2}, \mathrm{HNO}_{3}, \mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{NH}_{3}, \mathrm{NaOH}, \mathrm{Na}_{2} \mathrm{CO}_{3}$
(a) Identify the strong Bronsted-Lowry acids and strong Bronsted-Lowry bases.
(b) List those compounds in (a) that can behave as Brensted-Lowry acids with strengths lying between those of $\mathrm{H}_{3} \mathrm{O}^{+}$ and $\mathrm{H}_{2} \mathrm{O}$ .
(c) List those compounds in (a) that can behave as Bronsted-Lowry bases with strengths lying between those of $\mathrm{H}_{2} \mathrm{O}$ and $\mathrm{OH}^{-} .$

Problem 29

The odor of vinegar is due to the presence of acetic acid, $\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}$ , a weak acid. List, in order of descending concentration, all of the ionic and molecular species present in a $1-M$ aqueous solution of this acid.

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Problem 30

Household ammonia is a solution of the weak base $\mathrm{NH}_{3}$ water. List in order of descending concentration, all of the ionic and molecular species present in a $1-M$ aqueous solution of this base.

Problem 31

Explain why the ionization constant, $K_{a},$ for $\mathrm{H}_{2} \mathrm{SO}_{4}$ is larger than the ionization constant for $\mathrm{H}_{2} \mathrm{SO}_{3}$

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Problem 32

Explain why the ionization constant, $K_{\mathrm{a}},$ for HI is larger than the ionization constant for HF.

Problem 33

Gastric juice, the digestive fluid produced in the stomach, contains hydrochloric acid, HCl. Milk of Magnesia, a suspension of solid $\mathrm{Mg}(\mathrm{OH})_{2}$ in an aqueous medium, is sometimes used to neutralize excess stomach acid. Write a complete balanced equation for the neutralization, reaction, and identify the conjugate acid-base pairs.

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Problem 34

Nitric acid reacts with insoluble copper(II) oxide to form soluble copper(II) nitrate, $\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2},$ a compound that has been used to prevent the growth of algae in swimming pools. Write the balanced chemical equation for the reaction of an aqueous solution of HNO$_{3}$ with CuO.

Problem 35

What is the ionization constant at $25^{\circ} \mathrm{C}$ for the weak acid $\mathrm{CH}_{3} \mathrm{NH}_{3}^{+},$ the conjugate acid of the weak base $\mathrm{CH}_{3} \mathrm{NH}_{2}, K_{\mathrm{b}}=4.4 \times 10^{-4}$

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Problem 36

What is the ionization constant at $25^{\circ} \mathrm{C}$ for the weak acid $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}_{2}^{+},$ the conjugate acid of the weak base $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}, K_{\mathrm{b}}=5.9 \times 10^{-4} ?$

Problem 37

Which base, $\mathrm{CH}_{3} \mathrm{NH}_{2}$ or $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}$ , is the stronger base? Which conjugate acid, $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}_{2}+$ or $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}_{3}^{+},$ is the stronger acid?

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Problem 38

Which is the stronger acid, $\mathrm{NH}_{4}^{+}$ or HBrO?

Problem 39

Which is the stronger base, $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N}$ or $\mathrm{H}_{2} \mathrm{BO}_{3}^{-} ?$

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Problem 40

Predict which acid in each of the following pairs is the stronger and explain your reasoning for each.
$$\begin{array}{l}{\text { (a) } \mathrm{H}_{2} \mathrm{O} \text { or } \mathrm{HF}} \\ {\text { (b) } \mathrm{B}(\mathrm{OH})_{3} \text { or } \mathrm{Al}(\mathrm{OH})_{3}} \\ {\text { (c) } \mathrm{HSO}_{3}^{-} \text { or } \mathrm{HSO}_{4}^{-}} \\ {\text { (d) } \mathrm{NH}_{3} \text { or } \mathrm{H}_{2} \mathrm{S}} \\ {\text { (e) } \mathrm{H}_{2} \mathrm{O} \text { or } \mathrm{H}_{2} \mathrm{Te}}\end{array}$$

Problem 41

Predict which compound in each of the following pairs of compounds is more acidic and explain your
reasoning for each.
$$\begin{array}{l}{\text { (a) } \mathrm{HSO}_{4}^{-} \text { or } \mathrm{HSeO}_{4}^{-}} \\ {\text { (b) } \mathrm{NH}_{3} \text { or } \mathrm{H}_{2} \mathrm{O}} \\ {\text { (c) } \mathrm{PH}_{3} \text { or } \mathrm{HI}} \\ {\text { (d) } \mathrm{NH}_{3} \text { or } \mathrm{PH}_{3}} \\ {\text { (e) } \mathrm{H}_{2} \mathrm{S} \text { or } \mathrm{HBr}}\end{array}$$

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Problem 42

Rank the compounds in each of the following groups in order of increasing acidity or basicity, as indicated, and explain the order you assign.
$$\begin{array}{l}{\text { (a) acidity: HCl, HBr, HI }} \\ {\text { (b) basicity: } \mathrm{H}_{2} \mathrm{O}, \mathrm{OH}^{-}, \mathrm{H}^{-}, \mathrm{Cl}^{-}} \\ {\text { (c) basicity: } \mathrm{Mg}(\mathrm{OH})_{2}, \mathrm{Si}(\mathrm{OH})_{4}, \mathrm{ClO}_{3}(\mathrm{OH}) \text { (Hint: Formula could also be written as } \mathrm{HClO}_{4} )} \\ {\text { (d) acidity: } \mathrm{HF}, \mathrm{H}_{2} \mathrm{O}, \mathrm{NH}_{3}, \mathrm{CH}_{4}}\end{array}$$

Problem 43

Rank the compounds in each of the following groups in order of increasing acidity or basicated, as indicated, and explain the order you assign.
$$\begin{array}{l}{\text { (a) acidity: NaHSO_ }_{3}, \text { NaHSeO_ }_{3}, \text { NaHSO }_{4}} \\ {\text { (b) basicity: } \mathrm{BrO}_{2}^{-}, \quad \mathrm{ClO}_{2}^{-}, \quad \mathrm{IO}_{2}-}\end{array}$$
$$\begin{array}{l}{\text { (c) acidity: HOCl, HOBr, HOI }} \\ {\text { (d) acidity: HOCl, HOClO, HOClO___ }, \mathrm{HOClO}_{3}}\end{array}$$
$$\begin{array}{l}{\text { (e) basicity: } \mathrm{NH}_{2}^{-}, \text { HS }^{-}, \mathrm{HTe}^{-}, \mathrm{PH}_{2}^{-}} \\ {\text { (f) basicity: } \mathrm{BrO}^{-}, \mathrm{BrO}_{2}^{-}, \quad \mathrm{BrO}_{3}^{-}, \quad \mathrm{BrO}_{4}-}\end{array}$$

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Problem 44

Both HF and HCN ionize in water to a limited extent. Which of the conjugate bases, $\mathrm{F}^{-}$ or $\mathrm{CN}^{-},$ is the stronger base? See Table $14.2 .$

Problem 45

The active ingredient formed by aspirin in the body is salicylic acid, $C_{6} \mathrm{H}_{4} \mathrm{OH}\left(\mathrm{CO}_{2} \mathrm{H}\right) .$ The carboxyl group $\left(-\mathrm{CO}_{2} \mathrm{H}\right)$ acts a weak acid. The phenol group (an OH group bonded to an aromatic ring) acts as an acid but a much weaker acid. List, in order of descending concentration, all of the ionic and molecular species present in a $0.001-M$ aqueous solution of $\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{OH}\left(\mathrm{CO}_{2} \mathrm{H}\right)$

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Problem 46

What do we represent when we write:
$$\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{CH}_{3} \mathrm{CO}_{2}^{-}(a q) ?$$

Problem 47

Explain why equilibrium calculations are not necessary to determine ionic concentrations of certain strong electrolytes such as NaOH and HCl. Under what conditions are equilibrium calculations necessary as part of the determination of the concentrations of all ions of some other strong electrolytes in solution?

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Problem 48

Are the concentrations of hydronium ion and hydroxide ion in a solution of an acid or a base in water directly proportional or inversely proportional? Explain your answer.

Problem 49

What two common assumptions can simplify calculation of equilibrium concentrations in a solution of a weak acid?

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Problem 50

What two common assumptions can simplify calculation of equilibrium concentrations in a solution of a weak base?

Problem 51

Which of the following will increase the percent of $\mathrm{NH}_{3}$ that is converted to the ammonium ion in water (Hint: Use Lechâtelier's principle.)?
$$\begin{array}{l}{\text { (a) addition of NaOH }} \\ {\text { (b) addition of } \mathrm{HCl}} \\ {\text { (c) addition of } \mathrm{NH}_{4} \mathrm{Cl}}\end{array}$$

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Problem 52

Which of the following will increase the percent of HF that is converted to the fluoride ion in water?
$$\begin{array}{l}{\text { (a) addition of NaOH }} \\ {\text { (b) addition of } \mathrm{HCl}} \\ {\text { (c) addition of } \mathrm{NaF}}\end{array}$$

Problem 53

What is the effect on the concentrations of $\mathrm{NO}_{2}^{-},$ HNO_ $_{2},$ and OH - when the following are added to a solution of $\mathrm{KNO}_{2}$ in water:
$$\begin{array}{l}{\text { (a) } \mathrm{HCl}} \\ {\text { (b) } \mathrm{HNO}_{2}} \\ {\text { (c) } \mathrm{NaOH}} \\ {\text { (d) } \mathrm{NaCl}} \\ {\text { (e) KNO }}\end{array}$$
The equation for the equilibrium is:
$\mathrm{NO}_{2}^{-}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{HNO}_{2}(a q)+\mathrm{OH}^{-}(a q)$

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Problem 54

What is the effect on the concentration of hydrofluoric acid, hydronium ion, and fluoride ion when the
following are added to separate solutions of hydrofluoric acid?
$$\begin{array}{l}{\text { (a) } \mathrm{HCl}} \\ {\text { (b) } \mathrm{KF}} \\ {\text { (c) } \mathrm{NaCl}} \\ {\text { (d) } \mathrm{KOH}} \\ {\text { (e) HF }}\end{array}$$
The equation for the equilibrium is:
$\mathrm{HF}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{F}^{-}(a q)$

Problem 55

Why is the hydronium ion concentration in a solution that is 0.10$M$ in HCl and 0.10$M$ in HCOOH determined by the concentration of $\mathrm{HCl}$ ?

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Problem 56

From the equilibrium concentrations given, calculate $K_{\mathrm{a}}$ for each of the weak acids and $K_{\mathrm{b}}$ for each of the weak bases.
$$\begin{array}{l}{\text { (a) } \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H} :\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=1.34 \times 10^{-3} \mathrm{M}} \\ {\left[\mathrm{CH}_{3} \mathrm{CO}_{2}^{-}\right]=1.34 \times 10^{-3} \mathrm{M}} \\ {\left[\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\right]=9.866 \times 10^{-2} \mathrm{M}}\end{array}$$
$$\begin{array}{l}{\text { (b) } \mathrm{ClO}^{-} :\left[\mathrm{OH}^{-}\right]=4.0 \times 10^{-4} \mathrm{M}} \\ {[\mathrm{HClO}]=2.38 \times 10^{-5} \mathrm{M}} \\ {\left[\mathrm{ClO}^{-}\right]=0.273 \mathrm{M}}\end{array}$$
$$\begin{array}{l}{\text { (c) } \mathrm{HCO}_{2} \mathrm{H} :\left[\mathrm{HCO}_{2} \mathrm{H}\right]=0.524 M} \\ {\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=9.8 \times 10^{-3} M} \\ {\left[\mathrm{HCO}_{2}-\right]=9.8 \times 10^{-3} \mathrm{M}}\end{array}$$
$$\begin{array}{l}{\text { (d) } \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{3}^{+} :\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{3}^{+}\right]=0.233 \mathrm{M} ;} \\ {\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\right]=2.3 \times 10^{-3} \mathrm{M}} \\ {\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=2.3 \times 10^{-3} \mathrm{M}}\end{array}$$

Problem 57

From the equilibrium concentrations given, calculate $K_{a}$ for each of the weak acids and $K_{b}$ for each of the weak bases.
$$\begin{array}{l}{\text { (a) } \mathrm{NH}_{3} :\left[\mathrm{OH}^{-}\right]=3.1 \times 10^{-3} M} \\ {\left[\mathrm{NH}_{4}^{+}\right]=3.1 \times 10^{-3} M} \\ {\left[\mathrm{NH}_{3}\right]=0.533 M}\end{array}$$
$$\begin{array}{l}{\text { (b) HNO }_{2} :\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=0.011 \mathrm{M} ;} \\ {\left[\mathrm{NO}_{2}-\right]=0.0438 \mathrm{M} ;} \\ {\left[\mathrm{HNO}_{2}\right]=1.07 \mathrm{M}}\end{array}$$
$$\begin{array}{l}{\text { (c) }\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N} :\left[\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N}\right]=0.25 M} \\ {\left[\left(\mathrm{CH}_{3}\right)_{3} \mathrm{NH}^{+}\right]=4.3 \times 10^{-3} M ;} \\ {\left[\mathrm{OH}^{-}\right]=4.3 \times 10^{-3} \mathrm{M}}\end{array}$$
$$\begin{array}{l}{\text { (d) } \mathrm{NH}_{4}^{+} :\left[\mathrm{NH}_{4}^{+}\right]=0.100 \mathrm{M}} \\ {\left[\mathrm{NH}_{3}\right]=7.5 \times 10^{-6} M} \\ {\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=7.5 \times 10^{-6} \mathrm{M}}\end{array}$$

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Problem 58

Determine $K_{\mathrm{b}}$ for the nitrite ion, $\mathrm{NO}_{2}^{-} .$ In a 0.10 -M solution this base is 0.0015$\%$ ionized.

Problem 59

Determine $K_{\mathrm{a}}$ for hydrogen sulfate ion, HSO $_{4}^{-}$ In a 0.10 -M solution the acid is 29$\%$ ionized.

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Problem 60

Calculate the ionization constant for each of the following acids or bases from the ionization constant of its conjugate base or conjugate acid:
$$\begin{array}{l}{\text { (a) } \mathrm{F}^{-}} \\ {\text { (b) } \mathrm{NH}_{4}^{+}} \\ {\text { (c) } \mathrm{AsO}_{4}^{3-}} \\ {\text { (d) }\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}_{2}+} \\ {\text { (e) } \mathrm{NO}_{2}^{-}} \\ {\text { (f) } \mathrm{HC}_{2} \mathrm{O}_{4}^{-} \text { (as a base) }}\end{array}$$

Problem 61

Calculate the ionization constant for each of the following acids or bases from the ionization constant of its conjugate base or conjugate acid:
$$\begin{array}{l}{\text { (a) HTe - (as a base) }} \\ {\text { (b) }\left(\mathrm{CH}_{3}\right)_{3} \mathrm{NH}^{+}} \\ {\text { (c) HAsO_ }_{4}^{3-} \text { (as a base) }}\end{array}$$
$$\begin{array}{l}{\text { (d) } \mathrm{HO}_{2}^{-} \text { (as a base) }} \\ {\text { (e) } \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{3}+} \\ {\text { (f) } \mathrm{HSO}_{3}-\text { (as a base) }}\end{array}$$

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Problem 62

For which of the following solutions must we consider the ionization of water when calculating the pH or pOH?
$$\begin{array}{l}{\text { (a) } 3 \times 10^{-8} \mathrm{M} \mathrm{HNO}_{3}} \\ {\text { (b) } 0.10 \mathrm{g} \mathrm{HCl} \text { in } 1.0 \mathrm{L} \text { of solution }} \\ {\text { (c) } 0.00080 \mathrm{g} \mathrm{NaOH} \text { in } 0.50 \mathrm{L} \text { of solution }} \\ {\text { (d) } 1 \times 10^{-7} \mathrm{M} \mathrm{Ca}(\mathrm{OH})_{2}} \\ {\text { (e) } 0.0245 \mathrm{M} \mathrm{KNO}_{3}}\end{array}$$

Problem 63

Even though both $\mathrm{NH}_{3}$ and $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}$ are weak bases, NH_{3} is a much stronger acid than $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}$ . Which of the following is correct at equilibrium for a solution that is initially 0.10$M$ in $\mathrm{NH}_{3}$ M in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2} ?$
$$\begin{array}{l}{\text { (a) }\left[\mathrm{OH}^{-}\right]=\left[\mathrm{NH}_{4}^{+}\right]} \\ {\text { (b) }\left[\mathrm{NH}_{4}^{+}\right]=\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{3}^{+}\right]} \\ {\text { (c) }\left[\mathrm{OH}^{-}\right]=\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{3}+\right]} \\ {\text { (d) }\left[\mathrm{NH}_{3}\right]=\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\right]} \\ {\text { (e) both a and b are correct }}\end{array}$$

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Problem 64

Calculate the equilibrium concentration of the nonionized acids and all ions in a solution that is 0.25 $\mathrm{M}$ in $\mathrm{HCO}_{2} \mathrm{H}$ and 0.10 $\mathrm{M}$ in HClo.

Problem 65

Calculate the equilibrium concentration of the nonionized acl ions in a solution that is 0.134 $\mathrm{M}$ in $\mathrm{HNO}_{2}$ and 0.120 $\mathrm{M}$ in $\mathrm{HBrO}$

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Problem 66

Calculate the equilibrium concentration of the nonionized bases and all ions in a solution that is 0.25 $\mathrm{M}$ in $\mathrm{CH}_{3} \mathrm{NH}_{2}$ and 0.10 $\mathrm{M}$ in $\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}\left(K_{\mathrm{b}}=1.7 \times 10^{-9}\right)$

Problem 67

Calculate the equilibrium concentration of the nonionized bases and all ions in a solution that is 0.115 M in $\mathrm{NH}_{3}$ and 0.100 $\mathrm{M}$ in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}$

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Problem 68

Using the $K_{a}$ value of $1.4 \times 10^{-5},$ place $\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}^{3+}$ in the correct location in Figure 14.8

Problem 69

Calculate the concentration of all solute species in each of the following solutions of acids or bases. Assume that the ionization of water can be neglected, and show the change in the initial concentrations can be neglected. Ionization constants can be found in Appendix $\mathrm{H}$ and Appendix $1 .$
$$\begin{array}{l}{\text { (a) } 0.0092 \text { M HClO, a weak acid }} \\ {\text { (b) } 0.0784 M \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}, \text { a weak base }} \\ {\text { (c) } 0.0810 \mathrm{M} \mathrm{HCN} \text { , a weak acid }} \\ {\text { (d) } 0.11 \mathrm{M}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N} \text { , a weak base }} \\ {\text { (e) } 0.120 \mathrm{M} \mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}^{2+} \text { a weak acid, } K_{\mathrm{a}}=1.6 \times 10^{-7}}\end{array}$$

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Problem 70

Propionic acid, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}\left(K_{\mathrm{a}}=1.34 \times 10^{-5}\right),$ is used in the manufacture of calcium propionate, a food preservative. What is the hydronium ion concentration in a 0.698 -M solution of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}$ ?

Problem 71

White vinegar is a 5.0$\%$ by mass solution of acetic acid in water. If the density of white vinegar is 1.007 $\mathrm{g} / \mathrm{cm}^{3}$ , what is the pH?

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Problem 72

The ionization constant of lactic acid, $\mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{CO}_{2} \mathrm{H}$ , an acid found in the blood after strenuous exercise, is $1.36 \times 10^{-4} .$ If 20.0 g of lactic acid is used to make a solution with a volume of 1.00 $\mathrm{L}$ , what is the concentration
of hydronium ion in the solution?

Problem 73

Nicotine, $\mathrm{C}_{10} \mathrm{H}_{14} \mathrm{N}_{2},$ is a base that will accept two protons $\left(K_{1}=7 \times 10^{-7}, K_{2}=1.4 \times 10^{-11}\right) .$ What is the concentration of each species present in a $0.050-M$ solution of nicotine?

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Problem 74

The pH of a 0.20 - M solution of $\mathrm{HF}$ is $1.92 .$ Determine $K_{\mathrm{a}}$ for HF from these data.

Problem 75

The pH of a 0.15 - M solution of $\mathrm{HSO}_{4}^{-}$ is $1.43 .$ Determine $K_{\mathrm{a}}$ for $\mathrm{HSO}_{4}^{-}$ from these data.

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Problem 76

The pH of a $0.10-$ M solution of caffeine is 11.16 . Determine $K_{\mathrm{b}}$ for caffeine from these data:
$$\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{4} \mathrm{O}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{4} \mathrm{O}_{2} \mathrm{H}^{+}(a q)+\mathrm{OH}^{-}(a q)$$

Problem 77

The pH of a solution of household ammonia, a 0.950 M solution of $\mathrm{NH}_{3},$ is 11.612 . Determine $K_{\mathrm{b}}$ for $\mathrm{NH}_{3}$ from these data.

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Problem 78

Determine whether aqueous solutions of the following salts are acidic, basic, or neutral:
$$\begin{array}{l}{\text { (a) } \mathrm{Al}\left(\mathrm{NO}_{3}\right)_{3}} \\ {\text { (b) RbI }} \\ {\text { (c) } \mathrm{KHCO}_{2}} \\ {\text { (d) } \mathrm{CH}_{3} \mathrm{NH}_{3} \mathrm{Br}}\end{array}$$

Problem 79

Determine whether aqueous solutions of the following salts are acidic, basic, or neutral:
$$\begin{array}{l}{\text { (a) } \mathrm{FeCl}_{3}} \\ {\text { (b) } \mathrm{K}_{2} \mathrm{CO}_{3}} \\ {\text { (c) } \mathrm{NH}_{4} \mathrm{Br}} \\ {\text { (d) } \mathrm{KClO}_{4}}\end{array}$$

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Problem 80

Novocaine, $\mathrm{C}_{13} \mathrm{H}_{21} \mathrm{O}_{2} \mathrm{N}_{2} \mathrm{Cl}$ , is the salt of the base procaine and hydrochloric acid. The ionization constant for procaine is $7 \times 10^{-6} .$ Is a solution of novocaine acidic or basic? What are $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right],\left[\mathrm{OH}^{-}\right],$ and pH of a 2.0$\%$ solution by mass of novocaine, assuming that the density of the solution is 1.0 $\mathrm{g} / \mathrm{mL}$

Problem 81

Which of the following concentrations would be practically equal in a calculation of the equilibrium concentrations in a $0.134-M$ solution of $\mathrm{H}_{2} \mathrm{CO}_{3},$ a diprotic acid: $\left[\mathrm{OH}^{-}\right],\left[\mathrm{H}_{2} \mathrm{CO}_{3}\right],\left[\mathrm{HCO}_{3}-\right]$ $\left[\mathrm{CO}_{3}^{2-}\right] ?$ No calculations are needed to answer this question.

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Problem 82

Calculate the concentration of each species present in a $0.050-$ M solution of $\mathrm{H}_{2} \mathrm{S}$ .

Problem 83

Calculate the concentration of each species present in a 0.010-M solution of phthalic acid, $\mathrm{C}_{6} \mathrm{H}_{4}\left(\mathrm{CO}_{2} \mathrm{H}\right)_{2}$
$$\begin{array}{ll}{\mathrm{C}_{6} \mathrm{H}_{4}\left(\mathrm{CO}_{2} \mathrm{H}\right)_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{C}_{6} \mathrm{H}_{4}\left(\mathrm{CO}_{2} \mathrm{H}\right)\left(\mathrm{CO}_{2}\right)^{-}(a q)} & {K_{\mathrm{a}}=1.1 \times 10^{-3}} \\ {\mathrm{C}_{6} \mathrm{H}_{4}\left(\mathrm{CO}_{2} \mathrm{H}\right)\left(\mathrm{CO}_{2}\right)(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{C}_{6} \mathrm{H}_{4}\left(\mathrm{CO}_{2}\right)_{2}^{2-}(a q)} & {K_{\mathrm{a}}=3.9 \times 10^{-6}}\end{array}$$

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Problem 84

Salicylic acid, HOC $_{6} \mathrm{H}_{4} \mathrm{CO}_{2} \mathrm{H}$ , and its derivatives have been used as pain relievers for a long time. Salicylic acid occurs in small amounts in the leaves, bark, and roots of some vegetably historically in the bark of the willow tree). Extracts of these plants have been used as medications for centuries. The acid was first isolated in the laboratory in $1838 .$
(a) Both functional groups of salicylic acid ionize in water, with $K_{\mathrm{a}}=1.0 \times 10^{-3}$ for the $-\mathrm{CO}_{2} \mathrm{H}$ group and 4.2 $\times 10^{-13}$ for the $-\mathrm{OH}$ group. What is the pH of a saturated solution of the acid (solubility $=1.8 \mathrm{g} / \mathrm{L} )$
(b) Aspirin was discovered as a result of efforts to produce of salicylic acid that would not be irritating to the stomach lining. Aspirin is acetylsalicylic acid, $\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{CO}_{2} \mathrm{H}$ . The - $\mathrm{CO}_{2} \mathrm{H}$ functional group is still present, but its acidity is reduced, $K_{\mathrm{a}}=3.0 \times 10^{-4} .$ What is the ph of a solution of aspirin with the same concentration as a saturated solution of salicylic acid (See Part a).
(c) Under some conditions, aspirin reacts with water and forms a solution of salicylic acetic acetic acid: $\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{C}_{6} \mathrm{H}_{4} \mathrm{CO}_{2} \mathrm{H}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{HOC}_{6} \mathrm{H}_{4} \mathrm{CO}_{2} \mathrm{H}(a q)+\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(a q)$
i. Which of the acids, salicylic acid or acetic acid, produces more hydronium ions in such a solution?
ii. What are the concentrations of molecules and ions in a solution produced by the hyrrolysis of 0.50 $\mathrm{g}$ of appirin dissolved in enough water to give 75 $\mathrm{mL}$ of solution?

Problem 85

The ion HTe- is an amphiprotic species; it can act as either an acid or a base.
(a) What is $K_{a}$ for the acid reaction of HTe $^{-}$ with $\mathrm{H}_{2} \mathrm{O}$ ?
(b) What is $K_{\mathrm{b}}$ for the reaction in which HTe $^{-}$ functions as a base in water?
(c) Demonstrate whether or not the second ionization of $\mathrm{H}_{2} \mathrm{Te}$ can be neglected in the calculation of $\left[\mathrm{HTe}^{-}\right]$ in a 0.10 M solution of $\mathrm{H}_{2} \mathrm{Te.}$

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Problem 86

Explain why a buffer can be prepared from a mixture of $\mathrm{NH}_{4} \mathrm{Cl}$ and NaOH but not from $\mathrm{NH}_{3}$ and $\mathrm{NaOH}$

Problem 87

Explain why the pH does not change significantly when a small amount of an acid or a base is added to a solution that contains equal amounts of the acid $\mathrm{H}_{3} \mathrm{PO}_{4}$ and a salt of its conjugate base $\mathrm{NaH}_{2} \mathrm{PO}_{4}$

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Problem 88

Explain why the pH does not change significantly when a small amount of an acid or a base is added to a solution that contains equal amounts of the base $\mathrm{NH}_{3}$ and a salt of its conjugate acid $\mathrm{NH}_{4} \mathrm{Cl}$

Problem 89

What is $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]$ in a solution of 0.25$M \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}$ and 0.030 $\mathrm{M} \mathrm{NaCH}_{3} \mathrm{CO}_{2} ?$
$$\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{CH}_{3} \mathrm{CO}_{2}^{-}(a q) \quad K_{\mathrm{a}}=1.8 \times 10^{-5}$$

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Problem 90

What is $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]$ in a solution of 0.075$M \mathrm{HNO}_{2}$ and 0.030 $\mathrm{M} \mathrm{NaNO}_{2} ?$
$$\mathrm{HNO}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{NO}_{2}^{-}(a q) \quad K_{\mathrm{a}}=4.5 \times 10^{-5}$$

Problem 91

What is $\left[\mathrm{OH}^{-}\right]$ in a solution of 0.125$M \mathrm{CH}_{3} \mathrm{NH}_{2}$ and 0.130 $\mathrm{M} \mathrm{CH}_{3} \mathrm{NH}_{3} \mathrm{Cl}$ ?
$$\mathrm{CH}_{3} \mathrm{NH}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{CH}_{3} \mathrm{NH}_{3}^{+}(a q)+\mathrm{OH}^{-}(a q) \quad K_{\mathrm{b}}=4.4 \times 10^{-4}$$

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Problem 92

What is $\left[\mathrm{OH}^{-}\right]$ in a solution of 1.25$M \mathrm{NH}_{3}$ and 0.78 $\mathrm{M} \mathrm{NH}_{4} \mathrm{NO}_{3} ?$
$$\mathrm{NH}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{NH}_{4}^{+}(a q)+\mathrm{OH}^{-}(a q) \quad K_{\mathrm{b}}=1.8 \times 10^{-5}$$

Problem 93

What concentration of $\mathrm{NH}_{4} \mathrm{NO}_{3}$ is required to make $\left[\mathrm{OH}^{-}\right]=1.0 \times 10^{-5}$ in a $0.200-\mathrm{M}$ solution of $\mathrm{NH}_{3} ?$

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Problem 94

What concentration of $\mathrm{NaF}$ is required to make $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=2.3 \times 10^{-4}$ in a $0.300-\mathrm{M}$ solution of $\mathrm{HF} ?$

Problem 95

What is the effect on the concentration of acetic acid, hydronium ion, and acetate ion when the following are added to an acidic buffer solution of equal concentrations of acetic acid and sodium acetate:
$$\begin{array}{l}{\text { (a) } \mathrm{HCl}} \\ {\text { (b) } \mathrm{KCH}_{3} \mathrm{CO}_{2}} \\ {\text { (c) } \mathrm{NaCl}} \\ {\text { (d) } \mathrm{KOH}} \\ {\text { (e) } \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}}\end{array}$$

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Problem 96

What is the effect on the concentration of ammonia, hydroxide ion, and ammonium ion when the following are added to a basic buffer solution of equal concentrations of ammonia and ammonium nitrate:
$$\begin{array}{l}{\text { (a) } \mathrm{KI}} \\ {\text { (b) } \mathrm{NH}_{3}} \\ {\text { (c) } \mathrm{HI}} \\ {\text { (d) } \mathrm{NaOH}} \\ {\text { (e) } \mathrm{N} \mathrm{H}_{4} \mathrm{Cl}}\end{array}$$

Problem 97

What will be the pH of a buffer solution prepared from $0.20 \mathrm{mol} \mathrm{NH}_{3}, 0.40 \mathrm{mol} \mathrm{NH}_{4} \mathrm{NO}_{3},$ and just enough water to give 1.00 $\mathrm{L}$ of solution?

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Problem 98

Calculate the pH of a buffer solution prepared from 0.155 mol of phosphoric acid, 0.250 mole of $\mathrm{KH}_{2} \mathrm{PO}_{4}$ , and enough water to make 0.500 $\mathrm{L}$ of solution.

Problem 99

How much solid $\mathrm{NaCH}_{3} \mathrm{CO}_{2} \cdot 3 \mathrm{H}_{2} \mathrm{O}$ must be added to 0.300 $\mathrm{L}$ of a $0.50-\mathrm{M}$ acetic acid solution to give a buffer with a pH of 5.00$?$ (Hint: Assume a negligible change in volume as the solid is added.)

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Problem 100

What mass of $\mathrm{NH}_{4} \mathrm{Cl}$ must be added to 0.750 $\mathrm{L}$ of a $0.100-\mathrm{M}$ solution of $\mathrm{NH}_{3}$ to gue a buffer solution with a pH of 9.26$?$ (Hint: Assume a negligible change in volume as the solid is added.)

Problem 101

A buffer solution is prepared from equal volumes of 0.200$M$ acetic acid and 0.600$M$ sodium acetate. Use $1.80 \times 10^{-5}$ as $K_{\mathrm{a}}$ for acetic acid.
(a) What is the pH of the solution?
(b) Is the solution acidic or basic?
(c) What is the pH of a solution that results when 3.00 $\mathrm{mL}$ of 0.034 $\mathrm{M} \mathrm{HCl}$ is added to 0.200 $\mathrm{L}$ of the original buffer?

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Problem 102

A 5.36 -g sample of $\mathrm{NH}_{4} \mathrm{Cl}$ was added to 25.0 $\mathrm{mL}$ of 1.00 $\mathrm{M}$ NaOH and the resulting solution diluted to 0.100 $\mathrm{L}$
(a) What is the pH of this buffer solution?
(b) Is the solution acidic or basic?
(c) What is the pH of a solution that results when 3.00 $\mathrm{mL}$ of 0.034 $\mathrm{M} \mathrm{HCl}$ is added to the solution?

Problem 103

Which acid in Table 14.2 is most appropriate for preparation of a buffer solution with a pH of 3.1? Explain your choice.

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Problem 104

Which acid in Table 14.2 is most appropriate for preparation of a buffer solution with a pH of 3.77 . Explain your choice.

Problem 105

Which base in Table 14.3 is most appropriate for preparation of a buffer solution with a pH of 10.65$?$ Explain your choice.

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Problem 106

Which base in Table 14.3 is most appropriate for preparation of a buffer solution with a pH of 9.20$?$ Explain your choice.

Problem 107

Saccharin, $\mathrm{C}_{7} \mathrm{H}_{4} \mathrm{NSO}_{3} \mathrm{H},$ is a weak acid $\left(K_{\mathrm{a}}=2.1 \times 10^{-2}\right) .$ If 0.250 $\mathrm{L}$ of diet cola with a buffered pH of 5.48 was prepared from $2.00 \times 10^{-3} \mathrm{g}$ of sodium sacharide, $\mathrm{Na}\left(\mathrm{C}_{7} \mathrm{H}_{4} \mathrm{NSO}_{3}\right),$ what are the final concentrations of saccharine and sodium saccharide in the solution?

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Problem 108

What is the pH of 1.000 L of a solution of 100.0 g of glutamic acid $\left(\mathrm{C}_{5} \mathrm{H}_{9} \mathrm{NO}_{4}, \text { a diprotic acid; } K_{1}=8.5 \times\right.$ $10^{-5}, K_{2}=3.39 \times 10^{-10} )$ to which has been added 20.0 g of NaOH during the preparation of monosodium glutamate, the flavoring agent? What is the pH when exactly 1 mol of NaOH per mole of acid has been added?

Problem 109

Explain how to choose the appropriate acid-base indicator for the titration of a weak base with a strong acid.

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Problem 110

Explain why an acid-base indicator changes color over a range of pH values rather than at a specific pH.

Problem 111

Why can we ignore the contribution of water to the concentrations of $\mathrm{H}_{3} \mathrm{O}^{+}$ in the solutions of following acids:
$$\begin{array}{l}{0.0092 M \mathrm{HClO} \text { , a weak acid }} \\ {0.0810 \mathrm{M} \mathrm{HCN} \text { , a weak acid }} \\ {0.120 \mathrm{M} \mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}^{2+} \text { a weak acid, } K_{\mathrm{a}}=1.6 \times 10^{-7}}\end{array}$$
but not the contribution of water to the concentration of $\mathrm{OH}^{-} ?$

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Problem 112

Why can we ignore the contribution of water to the concentration of $\mathrm{OH}^{-}$ in a solution of the following bases:
$$\begin{array}{l}{0.0784 M \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}, \text { a weak base }} \\ {0.11 M\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N}, \text { a weak base }}\end{array}$$
but not the contribution of water to the concentration of $\mathrm{H}_{3} \mathrm{O}^{+} ?$

Problem 113

Draw a curve for a series of solutions of H. Plot $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]_{\text { total on the vertical axis and the total concentration of }}$ HF (the sum of the concentrations of bonized and nonionized HF molecules) on the horizontal axis. Let the total concentration of HF vary from $1 \times 10^{-10} M$ to $1 \times 10^{-2} \mathrm{M} .$

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Problem 114

Draw a curve similar to that shown in Figure 14.23 for a series of solutions of $\mathrm{NH}_{3}$ . Plot $\left[\mathrm{OH}^{-}\right]$ on the vertical axis and the total concentration of $\mathrm{NH}_{3}$ (bonized and nonionized $\mathrm{NH}_{3}$ molecules) on the horizontal axis. Let the total concentration of $\mathrm{NH}_{3}$ vary from $1 \times 10^{-10} \mathrm{M}$ to $1 \times 10^{-2} \mathrm{M} .$

Problem 115

Calculate the pH at the following points in a titration of 40 $\mathrm{mL}(0.040 \mathrm{L})$ of 0.100 $\mathrm{M}$ barbituric acid $\left(K_{\mathrm{a}}=9.8\right.$ $\times 10^{-5} )$ with 0.100$M \mathrm{KOH}$
$$\begin{array}{l}{\text { (a) no KOH added }} \\ {\text { (b) } 20 \mathrm{mL} \text { of KOH solution added }} \\ {\text { (c) } 39 \mathrm{mL} \text { of KOH solution added }} \\ {\text { (d) } 40 \mathrm{mL} \text { of KOH solution added }} \\ {\text { (e) } 41 \mathrm{mL} \text { of KOH solution added }}\end{array}$$

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Problem 116

The indicator dinitrophenol is an acid with a $K_{\mathrm{a}}$ of $1.1 \times 10^{-4} .$ In a $1.0 \times 10^{-4}-\mathrm{M}$ solution, it is colorless in acid and yellow in base. Calculate the pH range over which it goes from 10$\%$ ionized (colorless) to 90$\%$ ionized (yellow).