Chemistry: The Molecular Nature of Matter

Neil D. Jespersen, James E. Brady, Alison Hyslop

Chapter 16

Acid-Base Equilibria in Aqueous Solutions - all with Video Answers

Educators

Chapter Questions

Problem 1

Write the chemical equation for (a) the autoionization of water and (b) the equilibrium law for $K_{\mathrm{w}}$.

Sima Sarker

Sima Sarker

Numerade Educator

Problem 2

How are acidic, basic, and neutral solutions in water defined (a) in terms of $\left[\mathrm{H}^{+}\right]$ and $\left[\mathrm{OH}^{-}\right]$ and $(\mathbf{b})$ in terms of $\mathrm{pH}$ and $\mathrm{pOH}$ ?

Sima Sarker

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Problem 3

At $25^{\circ} \mathrm{C}$, how are the $\mathrm{pH}$ and $\mathrm{pOH}$ of a solution related to each other?

Sima Sarker

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Problem 4

Why do chemists use $\mathrm{pH}$ notation instead of the concentration of $\mathrm{H}^{+}$ ions?

Sima Sarker

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Problem 5

Explain how acids and bases suppress the ionization of water, often called the common ion effect.

David Collins

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Problem 6

Explain the leveling effect of water.

Sima Sarker

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Problem 7

Could you use the p-notation for the concentration of a very dilute solution of chloride ion for a solution made when a tablespoon of water is added to a gallon of water? How would it be defined?

David Collins

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Problem 8

List the strong acids.

Sima Sarker

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Problem 9

What chemical property is central to our classifying an acid as a strong acid?

David Collins

Numerade Educator

Problem 10

Explain the difference between strength and concentration of an acid.

Charles Thomas

Numerade Educator

Problem 11

Explain the difference between strength and concentration of an acid.

Charles Thomas

Numerade Educator

Problem 12

Some strong bases can be used to safely reduce stomach acidity (heartburn). What differentiates strong bases that are safe medicines from those that could cause irreparable harm?

David Collins

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Problem 13

Explain why we can ignore the autoionization of water in a $1.0 M$ solution of a strong acid.

Sima Sarker

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Problem 14

Write the general equation for the ionization of a weak acid, $\mathrm{H} A,$ in water. Give the equilibrium law corresponding to $K_{a}$.

Susan Hallstrom

Susan Hallstrom

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Problem 15

Which diagram best represents a weak acid? A strong acid? A nonelectrolyte?

Sima Sarker

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Problem 16

Why do we use equilibrium constants, $K_{\mathrm{a}}$ and $K_{\mathrm{b}}$, for weak acids and bases, but not for the strong acids and bases?

Sima Sarker

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Problem 17

Write the chemical equation for the ionization of each of the following weak acids in water. (For polyprotic acids, write only the equation for the first step in the ionization.)
(a) $\mathrm{HNO}_{2}$
(c) $\mathrm{HAsO}_{4}^{2-}$
(b) $\mathrm{H}_{3} \mathrm{PO}_{4}$
(d) $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{NH}^{+}$

Sima Sarker

Numerade Educator

Problem 18

For each of the acids in Review Question 16.17 write the appropriate $K_{\mathrm{a}}$ expression.

Sima Sarker

Numerade Educator

Problem 19

Write the general equation for the ionization of a weak base, $B$, in water. Give the equilibrium law corresponding to $K_{b}$.

Sima Sarker

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Problem 20

Write the chemical equation for the ionization of each of the following weak bases in water.
(a) $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}$
(c) $\mathrm{NO}_{2}^{-}$
(b) $\mathrm{AsO}_{4}^{3-}$
(d) $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{~N}_{2} \mathrm{H}_{2}$

Sima Sarker

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Problem 21

For each of the bases in Review Question $16.20,$ write the appropriate $K_{\mathrm{b}}$ expression.

David Collins

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Problem 22

The $\mathrm{p} K_{\mathrm{a}}$ of $\mathrm{HCN}$ is 9.31 and that of $\mathrm{HF}$ is $3.46 .$ Which is the stronger Brønsted base, $\mathrm{CN}^{-}$ or $\mathrm{F}^{-}$ ?

Sima Sarker

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Problem 23

Write the structural formulas for the conjugate acids of the following:

Sima Sarker

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Problem 24

Write the structural formulas for the conjugate bases of the following:

Sima Sarker

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Problem 25

How is percentage ionization defined? Write the equation.

Sima Sarker

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Problem 26

What criterion do we use to determine whether or not the equilibrium concentration of an acid or base will be effectively the same as its initial concentration when we calculate the $\mathrm{pH}$ of the solution?

David Collins

Numerade Educator

Problem 27

For which of the following are we permitted to make the assumption that the equilibrium concentration of the acid or base is the same as the initial concentration when we calculate the $\mathrm{pH}$ of the solution specified?
(a) $0.020 \mathrm{M} \mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$
(c) $0.002 \mathrm{M} \mathrm{N}_{2} \mathrm{H}_{4}$
(b) $0.10 \mathrm{M} \mathrm{CH}_{3} \mathrm{NH}_{2}$
(d) $0.050 \mathrm{M} \mathrm{HCHO}_{2}$

David Collins

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Problem 28

What is the quadratic formula? When is it appropriate to use it finding equilibrium concentrations?

Sima Sarker

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Problem 29

Aspirin is acetylsalicylic acid, a monoprotic acid whose $K_{\mathrm{a}}$ value is $3.3 \times 10^{-4} .$ Does a solution of the sodium salt of aspirin in water test acidic, basic, or neutral? Explain.

David Collins

Numerade Educator

Problem 30

The $K_{\mathrm{b}}$ value of the oxalate ion, $\mathrm{C}_{2} \mathrm{O}_{4}{ }^{2-},$ is $1.6 \times 10^{-10}$ Is a solution of $\mathrm{K}_{2} \mathrm{C}_{2} \mathrm{O}_{4}$ acidic, basic, or neutral? Explain.

Sima Sarker

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Problem 31

Consider the following compounds and suppose that $0.5 M$ solutions are prepared of each: $\mathrm{NaI}, \mathrm{NH}_{4} \mathrm{Br}, \mathrm{KF}$ $\mathrm{KCN}, \mathrm{KC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}, \mathrm{CsNO}_{3},$ and $\mathrm{KBr}$. Write the formulas of those that have solutions that are (a) acidic, (b) basic, and (c) neutral.

Sima Sarker

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Problem 32

Will an aqueous solution of $\mathrm{AlCl}_{3}$ turn litmus red or blue? Explain.

Sima Sarker

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Problem 33

A solution of hydrazinium acetate is slightly acidic. Without looking at the tables of equilibrium constants, is $K_{\mathrm{a}}$ for acetic acid larger or smaller than $K_{\mathrm{b}}$ for hydrazine? Justify your answer.

Sima Sarker

Numerade Educator

Problem 34

When ammonium nitrate is added to a suspension of magnesium hydroxide in water, the $\mathrm{Mg}(\mathrm{OH})_{2}$ dissolves. Write a net ionic equation to show how this occurs.

Sima Sarker

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Problem 35

To form a buffer, two substances are needed. How are these substances related?

Sima Sarker

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Problem 36

Write ionic equations that illustrate how each pair of compounds can serve as a buffer pair.
(a) $\mathrm{H}_{2} \mathrm{CO}_{3}$ and $\mathrm{NaHCO}$ (the "carbonate" buffer in blood)
(b) $\mathrm{NaH}_{2} \mathrm{PO}_{4}$ and $\mathrm{Na}_{2} \mathrm{HPO}_{4}$ (the "phosphate" buffer inside body cells)
(c) $\mathrm{NH}_{4} \mathrm{Cl}$ and $\mathrm{NH}_{3}$
(d) Phenol and sodium phenolate

David Collins

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Problem 37

The hydrogen phosphate ion is able to act as a buffer all by itself. Write chemical equations that show how this ion reacts with (a) $\mathrm{H}^{+}$ and $(\mathbf{b}) \mathrm{OH}^{-} .$

David Collins

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Problem 38

When sulfur dioxide, an air pollutant from the burning of sulfur-containing coal or oil, dissolves in water, an acidic solution is formed that can be viewed as containing sulfurous acid, $\mathrm{H}_{2} \mathrm{SO}_{3}$
$$
\mathrm{H}_{2} \mathrm{O}+\mathrm{SO}_{2}(g) \rightleftharpoons \mathrm{H}_{2} \mathrm{SO}_{3}(a q)
$$
Write the expression for $K_{a_{1}}$ and $K_{a_{2}}$ for sulfurous acid.

Sima Sarker

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Problem 39

Which diagram best describes a diprotic acid with the first proton a strong acid and the second proton a weak acid?

David Collins

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Problem 40

Citric acid, found in citrus fruits, is a triprotic acid, $\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7} .$ Write chemical equations for the three-step ionization of this acid in water and write the three $K_{\mathrm{a}}$ expressions (equilibrium laws).

Sima Sarker

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Problem 41

What simplifying assumptions do we usually make in working problems involving the ionization of polyprotic acids? Why are they usually valid? Under what conditions do they fail?

David Collins

Numerade Educator

Problem 42

Write the equations for the chemical equilibria that exist in solutions of (a) $\mathrm{Na}_{2} \mathrm{SO}_{3},$ (b) $\mathrm{Na}_{3} \mathrm{PO}_{4},$ and $(\mathbf{c})$ $\mathrm{K}_{2} \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6}$

David Collins

Numerade Educator

Problem 43

What simplifying assumptions do we usually make in working problems involving equilibria of salts of polyprotic acids? Why are they usually valid? Under what conditions do they fail?

David Collins

Numerade Educator

Problem 44

Define the terms equivalence point and end point as they apply to an acid-base titration.

David Collins

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Problem 45

Will the solution be acidic, neutral, or basic at the equivalence point for
(a) a formic acid solution that is titrated with sodium hydroxide?
(b) a solution of hydrazine that is titrated with hydrochloric acid?
(c) a solution of hydrochloric acid that is titrated with sodium hydroxide?

Sima Sarker

Numerade Educator

Problem 46

Qualitatively, describe how an acid-base indicator works. Why do we want to use a minimum amount of indicator in a titration?

David Collins

Numerade Educator

Problem 47

If you use methyl orange in the titration of $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ with $\mathrm{NaOH}$, will the end point of the titration correspond to the equivalence point? If not, suggest a better indicator for this titration. Justify your answer.

David Collins

Numerade Educator

Problem 48

Using the list of indicators in Table 16.7 , choose the appropriate indicators for the titrations depicted in Figures 16.8 and 16.9

David Collins

Numerade Educator

Problem 49

Calculate the $\left[\mathrm{H}^{+}\right], \mathrm{pH},$ and $\mathrm{pOH}$ in each of the following solutions in which the hydroxide ion concentrations are
(a) $0.0068 M$
(c) $1.6 \times 10^{-8} \mathrm{M}$
(b) $6.4 \times 10^{-5} M$
(d) $8.2 \times 10^{-12} M$

Sima Sarker

Numerade Educator

Problem 50

Calculate the $\left[\mathrm{OH}^{-}\right], \mathrm{pH},$ and $\mathrm{pOH}$ for each of the following solutions in which the $\mathrm{H}^{+}$ concentrations are
(a) $3.5 \times 10^{-7} M$
(c) $2.5 \times 10^{-11} M$
(b) $0.0017 M$
(d) $7.9 \times 10^{-2} M$

Sima Sarker

Numerade Educator

Problem 51

Calculate the molar concentrations of $\mathrm{H}^{+}$ and $\mathrm{OH}^{-}$ in solutions that have the following $\mathrm{pH}$ values.
(a) 8.14
(b) 2.56
(c) 11.25
(d) 13.28
(e) 6.70

Sima Sarker

Numerade Educator

Problem 52

Calculate the molar concentrations of $\mathrm{H}^{+}$ and $\mathrm{OH}^{-}$ in solutions that have the following $\mathrm{pH}$ values.
(a) 12.67
(b) 5.18
(c) 11.55
(d) 4.22
(e) 6.06

Sima Sarker

Numerade Educator

Problem 53

Calculate the molar concentrations of $\mathrm{H}^{+}$ and $\mathrm{OH}^{-}$ in solutions that have the following $\mathrm{pOH}$ values.
(a) 7.19
(b) 1.26
(c) 10.85
(d) 13.15
(e) 5.24

Sima Sarker

Numerade Educator

Problem 54

Calculate the molar concentrations of $\mathrm{H}^{+}$ and $\mathrm{OH}^{-}$ in solutions that have the following $\mathrm{pOH}$ values.
(a) 12.27
(b) 6.14
(c) 10.65
(d) 4.28
(e) 3.76

Sima Sarker

Numerade Educator

Problem 55

A certain brand of beer had a $\mathrm{H}^{+}$ concentration equal to $1.9 \times 10^{-5} \mathrm{~mol} \mathrm{~L}^{-1}$. What is the $\mathrm{pH}$ of the beer?

Sima Sarker

Numerade Educator

Problem 56

A soft drink was put on the market with $\left[\mathrm{H}^{+}\right]=1.4 \times$ $10^{-5} \mathrm{~mol} \mathrm{~L}^{-1}$. What is its $\mathrm{pH}$ ?

Sima Sarker

Numerade Educator

Problem 57

A sample of Windex had a $\left[\mathrm{OH}^{-}\right]=6.3 \times 10^{-5} \mathrm{~mol} \mathrm{~L}^{-1}$ What is the $\mathrm{oH}$ of the sample?

Sima Sarker

Numerade Educator

Problem 58

Bases tend to be used for cleaning. A solution of Tide laundry detergent had a $\left[\mathrm{OH}^{-}\right]=1.6 \times 10^{-4} \mathrm{~mol} \mathrm{~L}^{-1}$. What is the $\mathrm{pH}$ of the sample?

Sima Sarker

Numerade Educator

Problem 59

Deuterium oxide, $\mathrm{D}_{2} \mathrm{O},$ ionizes like water. At $20^{\circ} \mathrm{C}$ its $K_{\mathrm{w}}$ or ion product constant, analogous to that of water, is $8.9 \times 10^{-16} .$ Calculate $\left[\mathrm{D}^{+}\right]$ and $\left[\mathrm{OD}^{-}\right]$ in deuterium oxide at $20^{\circ} \mathrm{C}$. Calculate also the $\mathrm{pD}$ and the $\mathrm{pOD}$. What would be the neutral $\mathrm{pD}$ ?

Sima Sarker

Numerade Educator

Problem 60

At the temperature of the human body, $37^{\circ} \mathrm{C}$, the value of $K_{\mathrm{w}}$ is $2.5 \times 10^{-14} .$ Calculate $\left[\mathrm{H}^{+}\right],\left[\mathrm{OH}^{-}\right], \mathrm{pH},$ and $\mathrm{pOH}$ of pure water at this temperature. What is the relationship between $\mathrm{pH}, \mathrm{pOH},$ and $\mathrm{p} K_{\mathrm{w}}$ at this temperature? Is $\mathrm{pH} 7.00$ water neutral at this temperature?

Sima Sarker

Numerade Educator

Problem 61

The interaction of water droplets in rain with carbon dioxide that is naturally present in the atmosphere causes rain water to be slightly acidic because $\mathrm{CO}_{2}$ is an acid anhydride. As a result, pure clean rain has a pH of about 5.7. What are the hydrogen ion and hydroxide ion concentrations in this rain water?

Sima Sarker

Numerade Educator

Problem 62

"Acid rain" forms when rain falls through air polluted by oxides of sulfur and nitrogen. Trees and plants are affected if the acid rain has a pH of 3.5 or lower. What is the hydrogen ion concentration in acid rain that has a $\mathrm{pH}$ of 3.16 ? What is the $\mathrm{pH}$ of a solution having twice your calculated hydrogen ion concentration?

Sima Sarker

Numerade Educator

Problem 63

What is the concentration of $\mathrm{H}^{+}$ in $0.00065 \mathrm{M} \mathrm{HNO}_{3} ?$ What is the $\mathrm{pH}$ of this solution? What is the $\mathrm{OH}^{-}$ concentration in this solution?

Sima Sarker

Numerade Educator

Problem 64

What is the concentration of $\mathrm{H}^{+}$ in $0.031 \mathrm{M} \mathrm{HClO}_{4} ?$ What is the $\mathrm{pH}$ of the solution? What is the $\mathrm{OH}^{-}$ concentration in the solution? By how much does the pH change if the concentration of $\mathrm{H}^{+}$ is doubled?

Sima Sarker

Numerade Educator

Problem 65

A sodium hydroxide solution is prepared by dissolving $6.0 \mathrm{~g} \mathrm{NaOH}$ in $1.00 \mathrm{~L}$ of solution. What is the molar concentration of $\mathrm{OH}^{-}$ in the solution? What are the $\mathrm{pOH}$ and the $\mathrm{pH}$ of the solution? What is the hydrogen ion concentration in the solution?

Sima Sarker

Numerade Educator

Problem 66

A solution was made by dissolving $0.837 \mathrm{~g} \mathrm{Ba}(\mathrm{OH})_{2}$ in 100 mL final volume. What is the molar concentration of $\mathrm{OH}^{-}$ in the solution? What are the $\mathrm{pOH}$ and the $\mathrm{pH}$ ? What is the hydrogen ion concentration in the solution?

Sima Sarker

Numerade Educator

Problem 67

A solution of $\mathrm{Ca}(\mathrm{OH})_{2}$ has a measured $\mathrm{pH}$ of 11.60 . What is the molar concentration of the $\mathrm{Ca}(\mathrm{OH})_{2}$ in the solution? What is the molar concentration of $\mathrm{Ca}(\mathrm{OH})_{2}$ if the solution is diluted so that the $\mathrm{pH}$ is $10.60 ?$

Sima Sarker

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Problem 68

A solution of HCl has a pH of 2.50 . How many grams of $\mathrm{HCl}$ are there in $0.250 \mathrm{~L}$ of this solution? How many grams of $\mathrm{HCl}$ are in $250 \mathrm{~mL}$ of an $\mathrm{HCl}$ solution that has twice this $\mathrm{pH}$ ?

Vishal Sharma

Numerade Educator

Problem 69

In a $0.0020 \mathrm{M}$ solution of $\mathrm{NaOH}$, how many moles per liter of $\mathrm{OH}^{-}$ come from the ionization of water?

David Collins

Numerade Educator

Problem 70

In a certain solution of $\mathrm{HCl}$, the ionization of water contributes $3.4 \times 10^{-11}$ moles per liter to the $\mathrm{H}^{+}$ concentration. What is the total $\mathrm{H}^{+}$ concentration in the solution?

David Collins

Numerade Educator

Problem 71

A solution was prepared with 2.64 micrograms of $\mathrm{Ba}(\mathrm{OH})_{2}$ in 1.00 liter of water. What is the $\mathrm{pH}$ of the solution, and what concentration of hydrogen ions is provided by the ionization of water?

David Collins

Numerade Educator

Problem 72

What is the $\mathrm{pH}$ of a $3.0 \times 10^{-7} \mathrm{M}$ solution of $\mathrm{HCl}$ ? What concentration of hydrogen ions is provided by the ionization of water?

Sima Sarker

Numerade Educator

Problem 73

Rhododendrons are shrubs that produce beautiful flowers in the springtime. They only grow well in soil that has a $\mathrm{pH}$ that is 5.5 or slightly lower. What is the hydrogen ion concentration in the soil moisture if the $\mathrm{pH}$ is 5.5 ?

Sima Sarker

Numerade Educator

Problem 74

As eggs age, the $\mathrm{pH}$ of the egg white increases from about 7.9 to 9.3 as the carbon dioxide diffuses out of the egg. What is the hydrogen ion concentration in an egg, if the $\mathrm{pH}$ is 8.3?

Sima Sarker

Numerade Educator

Problem 75

The $K_{\mathrm{a}}$ for $\mathrm{HF}$ is $3.5 \times 10^{-4}$. What is the $K_{\mathrm{b}}$ for $\mathrm{F}^{-}$ ?

Sima Sarker

Numerade Educator

Problem 76

The barbiturate ion, $\mathrm{C}_{4} \mathrm{H}_{3} \mathrm{~N}_{2} \mathrm{O}_{3},$ has $K_{\mathrm{b}}=1.0 \times 10^{-10}$ What is the $K_{\mathrm{a}}$ for barbituric acid?

Sima Sarker

Numerade Educator

Problem 77

Iodic acid, $\mathrm{HIO}_{3},$ has a $\mathrm{p} K_{\mathrm{a}}$ of 0.77 (a) What are the formula and the $K_{\mathrm{b}}$ of its conjugate base? (b) Is its conjugate base a stronger or a weaker base than the acetate ion?

Sima Sarker

Numerade Educator

Problem 78

Lactic acid, $\mathrm{HC}_{3} \mathrm{H}_{5} \mathrm{O}_{3}$, is responsible for the sour taste of old milk. At $25^{\circ} \mathrm{C}$, its $K_{\mathrm{a}}=1.4 \times 10^{-4}$. (a) What is the $K_{\mathrm{b}}$ of its conjugate base, the lactate ion, $\mathrm{C}_{3} \mathrm{H}_{5} \mathrm{O}_{3}^{-} ?(\mathbf{b})$ Is its conjugate base a stronger or a weaker base than the acetate ion?

Sima Sarker

Numerade Educator

Problem 79

A $1.0 M$ solution of acetic acid has a $\mathrm{pH}$ of 2.37 . What percentage of the acetic acid is ionized in the solution?

Sima Sarker

Numerade Educator

Problem 80

A $0.250 \mathrm{M}$ solution of $\mathrm{NH}_{3}$ has a pH of 11.32 . What percentage of the ammonia is ionized in this solution?

Sima Sarker

Numerade Educator

Problem 81

A $0.20 M$ solution of a weak acid, $\mathrm{H} A$, has a $\mathrm{pH}$ of 3.22 . What is the percentage ionization of the acid? What is the value of $K_{\mathrm{a}}$ for the acid?

Sima Sarker

Numerade Educator

Problem 82

A $0.15 M$ solution of an acid found in milk has a $\mathrm{pH}$ of 2.80. What is the percentage ionization of the acid? What is the $K_{\mathrm{a}}$ for the acid?

Sima Sarker

Numerade Educator

Problem 83

A $0.12 M$ solution of a weak base is $0.012 \%$ ionized. What is the $\mathrm{pH}$ of the solution? What is the value of $K_{\mathrm{b}}$ for this base?

Sima Sarker

Numerade Educator

Problem 84

If a weak base is $0.030 \%$ ionized in $0.030 \mathrm{M}$ solution, what is the $\mathrm{pH}$ of the solution? What is the value of $K_{\mathrm{b}}$ for the base?

David Collins

Numerade Educator

Problem 85

Iodic acid, $\mathrm{HIO}_{3}$, is an important oxidizing agent and a moderately strong acid. In a $0.100 \mathrm{M}$ solution, $\left[\mathrm{H}^{+}\right]=7.1$ $\times 10^{-2} \mathrm{~mol} \mathrm{~L}^{-1} .$ Calculate the $K_{\mathrm{a}}$ and $\mathrm{p} K_{\mathrm{a}}$ for iodic acid.

Sima Sarker

Numerade Educator

Problem 86

Chloroacetic acid, $\mathrm{HC}_{2} \mathrm{H}_{2} \mathrm{O}_{2} \mathrm{Cl}$, is a stronger monoprotic acid than acetic acid. In a $0.10 M$ solution, the $\mathrm{pH}$ is $1.96 .$ Calculate the $K_{\mathrm{a}}$ and $\mathrm{p} K_{\mathrm{a}}$ for chloroacetic acid.

Sima Sarker

Numerade Educator

Problem 87

Ethylamine, $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}$, has a strong, pungent odor similar to that of ammonia. Like ammonia, it is a Brønsted base. A $0.10 M$ solution has a $\mathrm{pH}$ of $11.87 .$ Calculate the $K_{\mathrm{b}}$ and $\mathrm{p} K_{\mathrm{b}}$ for ethylamine. What is the percentage ionization of ethylamine in this solution?

Sima Sarker

Numerade Educator

Problem 88

Hydroxylamine, $\mathrm{HONH}_{2}$, like ammonia, is a Brønsted base. A $0.15 M$ solution has a pH of 10.11 . What are the $K_{\mathrm{b}}$ and $\mathrm{p} K_{\mathrm{b}}$ values for hydroxylamine? What is the percentage ionization of the $\mathrm{HONH}_{2}$ ?

David Collins

Numerade Educator

Problem 89

What are the concentrations of all the solute species in $0.150 \mathrm{M}$ lactic acid, $\mathrm{HC}_{3} \mathrm{H}_{5} \mathrm{O}_{2}$ ? What is the $\mathrm{pH}$ of the solution? This acid has a $K_{\mathrm{a}}=1.4 \times 10^{-4}$.

Sima Sarker

Numerade Educator

Problem 90

What are the concentrations of all the solute species in a 1.0 $M$ solution of hydrogen peroxide, $\mathrm{H}_{2} \mathrm{O}_{2}$ ? What is the $\mathrm{pH}$ of the solution? $\mathrm{For} \mathrm{H}_{2} \mathrm{O}_{2}, K_{\mathrm{a}}=2.4 \times 10^{-12}$

Sima Sarker

Numerade Educator

Problem 91

Codeine, a cough suppressant extracted from crude opium, is a weak base with a $\mathrm{p} K_{\mathrm{b}}$ of 5.80 . What will be the $\mathrm{pH}$ of a $0.020 \mathrm{M}$ solution of codeine?

Sima Sarker

Numerade Educator

Problem 92

Pyridine, $\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{~N},$ is a bad-smelling liquid that is a weak base in water. Its $\mathrm{p} K_{\mathrm{b}}$ is 8.77 . What is the $\mathrm{pH}$ of a $0.20 \mathrm{M}$ aqueous solution of this compound?

Sima Sarker

Numerade Educator

Problem 93

A solution of acetic acid has a pH of 2.54 . What is the concentration of acetic acid in this solution?

Sima Sarker

Numerade Educator

Problem 94

How many moles of $\mathrm{NH}_{3}$ must be dissolved in water to give $500.0 \mathrm{~mL}$ of solution with a $\mathrm{pH}$ of 11.22 ?

Sima Sarker

Numerade Educator

Problem 95

What is the $\mathrm{pH}$ of a $0.0050 \mathrm{M}$ solution of sodium cyanide?

Sima Sarker

Numerade Educator

Problem 96

What is the $\mathrm{pH}$ of a $0.020 \mathrm{M}$ solution of chloroacetic acid, for which $K_{a}=1.4 \times 10^{-3}$ ?

David Collins

Numerade Educator

Problem 97

The compound para-aminobenzoic acid (PABA) is a powerful sun-screening agent whose salts were once used widely in sun tanning and screening lotions. The parent acid, which we may symbolize as $\mathrm{H}-\mathrm{Paba}$, is a weak acid with a $\mathrm{p} K_{\mathrm{a}}$ of 4.92 (at $25^{\circ} \mathrm{C}$ ). What are the $\left[\mathrm{H}^{+}\right]$ and $\mathrm{pH}$ of a $0.030 \mathrm{M}$ solution of this acid?

Sima Sarker

Numerade Educator

Problem 98

Barbituric acid, $\mathrm{HC}_{4} \mathrm{H}_{3} \mathrm{~N}_{2} \mathrm{O}_{3}$ (which we will abbreviate H-Bar), was discovered by the Nobel Prize-winning organic chemist Adolph von Bayer and named after his friend, Barbara. It is the parent compound of widely used sleeping drugs, the barbiturates. Its $\mathrm{p} K_{\mathrm{a}}$ is 4.01 . What are the $\left[\mathrm{H}^{+}\right]$ and $\mathrm{pH}$ of a $0.020 \mathrm{M}$ solution of $\mathrm{H}-\mathrm{Bar}$ ?

Sima Sarker

Numerade Educator

Problem 99

Calculate the $\mathrm{pH}$ of $0.20 \mathrm{M} \mathrm{NaCN}$. What is the concentration of HCN in the solution?

Sima Sarker

Numerade Educator

Problem 100

Calculate the $\mathrm{pH}$ of $0.40 \mathrm{M} \mathrm{KNO}_{2}$. What is the concentration of $\mathrm{HNO}_{2}$ in the solution?

Sima Sarker

Numerade Educator

Problem 101

Calculate the $\mathrm{pH}$ of $0.15 \mathrm{M} \mathrm{CH}_{3} \mathrm{NH}_{3} \mathrm{Cl}$. For methylamine, $\mathrm{CH}_{3} \mathrm{NH}_{2}, K_{\mathrm{b}}=4.5 \times 10^{-4}$

Sima Sarker

Numerade Educator

Problem 102

Calculate the $\mathrm{pH}$ of $0.10 \mathrm{M}$ hydrazinium chloride, $\mathrm{N}_{2} \mathrm{H}_{5} \mathrm{Cl} .$

Sima Sarker

Numerade Educator

Problem 103

A $0.18 M$ solution of the sodium salt of nicotinic acid (also known pharmaceutically as niacin) has a pH of 9.05. What is the value of $K_{\mathrm{a}}$ for nicotinic acid?

David Collins

Numerade Educator

Problem 104

A weak base $B$ forms the salt $B \mathrm{HCl},$ composed of the ions $B \mathrm{H}^{+}$ and $\mathrm{Cl}^{-}$. A $0.15 \mathrm{M}$ solution of the salt has a $\mathrm{pH}$ of $4.28 .$ What is the value of $K_{\mathrm{b}}$ for the base $B$ ?

David Collins

Numerade Educator

Problem 105

Liquid chlorine bleach is really nothing more than a solution of sodium hypochlorite, $\mathrm{NaOCl}$, in water. Usually, the concentration is approximately $5.1 \% \mathrm{NaOCl}$ by weight. Use this information to calculate the approximate $\mathrm{pH}$ of a bleach solution, assuming no other solutes are in the solution except $\mathrm{NaOCl}$. (Assume the bleach has a density of $1.0 \mathrm{~g} / \mathrm{mL}$.)

David Collins

Numerade Educator

Problem 106

The conjugate acid of a molecular base has the general formula $B \mathrm{H}^{+}$ and a $\mathrm{p} K_{\mathrm{a}}$ of $5.00 .$ A solution of a salt of this cation, $B \mathrm{H} Y$, tests slightly basic. Will the conjugate acid of $Y^{-}, \mathrm{H} Y$, have a $\mathrm{p} K_{\mathrm{a}}$ greater than 5.00 or less than 5.00? Explain.

David Collins

Numerade Educator

Problem 107

What is the $\mathrm{pH}$ of a solution that contains $0.15 \mathrm{M}$ $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ and $0.25 \mathrm{M} \mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}$ ? Use $K_{\mathrm{a}}=1.8 \times$ $10^{-5}$ for $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$

Sima Sarker

Numerade Educator

Problem 108

A buffer is prepared containing $0.25 \mathrm{MNH}_{3}$ and $0.45 \mathrm{M}$ $\mathrm{NH}_{4}^{+} .$ Calculate the $\mathrm{pH}$ of the buffer using the $K_{\mathrm{b}}$ for $\mathrm{NH}_{3}$.

Sima Sarker

Numerade Educator

Problem 109

Rework Review Problem 16.107 using the $K_{\mathrm{b}}$ for the acetate ion.

Sima Sarker

Numerade Educator

Problem 110

Calculate the $\mathrm{pH}$ of the buffer in Review Problem 16.108 using the $K_{\mathrm{a}}$ for $\mathrm{NH}_{4}^{+}$.

Sima Sarker

Numerade Educator

Problem 111

By how much will the $\mathrm{pH}$ change if $0.025 \mathrm{~mol}$ of $\mathrm{HCl}$ is added to $1.00 \mathrm{~L}$ of the buffer in Review Problem $16.107 ?$

Sima Sarker

Numerade Educator

Problem 112

By how much will the $\mathrm{pH}$ change if $25.0 \mathrm{~mL}$ of $0.20 \mathrm{M}$ $\mathrm{NaOH}$ is added to $0.500 \mathrm{~L}$ of the buffer in Review Problem $16.108 ?$

David Collins

Numerade Educator

Problem 113

Certain proteolytic enzymes react in alkaline solutions. One of these enzymes produces 1.8 micromoles of hydrogen ions per second in a $2.50 \mathrm{~mL}$ portion of a buffer composed of $0.25 \mathrm{M} \mathrm{NH}_{3}$ and $0.20 \mathrm{M} \mathrm{NH}_{4} \mathrm{Cl}$. By how much will the concentrations of the $\mathrm{NH}_{3}$ and $\mathrm{NH}_{4}^{+}$ ions change after the reaction has run for 35 seconds?

Sima Sarker

Numerade Educator

Problem 114

A hydrolytic enzyme consumes $1.8 \times 10^{-7}$ moles of hydrogen ions per minute in $2.50 \mathrm{~L}$ of a buffer that contained $0.15 \mathrm{M} \mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ and $0.25 \mathrm{M} \mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}$. By how much did the concentrations of $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ and $\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}$ change after the enzyme reacted for 3.45 minutes?

Sima Sarker

Numerade Educator

Problem 115

What are the initial and final $\mathrm{pH}$ values for the buffer in Review Problem 16.113? What is the change in pH?

David Collins

Numerade Educator

Problem 116

What are the initial and final $\mathrm{pH}$ values for the buffer in Review Problem $16.114 ?$ What is the change in $\mathrm{pH}$ ?

David Collins

Numerade Educator

Problem 117

How many grams of sodium acetate, $\mathrm{NaC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$, would have to be added to $1.0 \mathrm{~L}$ of $0.15 \mathrm{M}$ acetic acid (p $K_{\mathrm{a}} 4.74$ ) to make the solution a buffer for $\mathrm{pH} 4.00$ ?

Sima Sarker

Numerade Educator

Problem 118

How many grams of sodium formate, $\mathrm{NaCHO}_{2}$, would have to be dissolved in $1.0 \mathrm{~L}$ of $0.12 \mathrm{M}$ formic acid $\left(\mathrm{p} K_{\mathrm{a}} 3.74\right)$ to make the solution a buffer for $\mathrm{pH}$ $3.50 ?$

Sima Sarker

Numerade Educator

Problem 119

Suppose $30.00 \mathrm{~mL}$ of $0.100 \mathrm{M} \mathrm{HCl}$ is added to an acetate buffer prepared by dissolving $0.100 \mathrm{~mol}$ of acetic acid and $0.110 \mathrm{~mol}$ of sodium acetate in $0.100 \mathrm{~L}$ of solution. What are the initial and final $\mathrm{pH}$ values? What would be the $\mathrm{pH}$ if the same amount of $\mathrm{HCl}$ solution were added to $125 \mathrm{~mL}$ of pure water?

David Collins

Numerade Educator

Problem 120

How many milliliters of $0.15 M \mathrm{HCl}$ would have to be added to the original $0.100 \mathrm{~L}$ of the buffer described in Review Problem 16.108 to make the $\mathrm{pH}$ decrease by $0.05 \mathrm{pH}$ unit? How many milliliters of the same $\mathrm{HCl}$ solution would, if added to $0.100 \mathrm{~L}$ of pure water, make the $\mathrm{pH}$ decrease by $0.05 \mathrm{pH}$ unit?

David Collins

Numerade Educator

Problem 121

Calculate the concentrations of all the solute species in a $0.15 M$ solution of ascorbic acid (vitamin C). What is the $\mathrm{pH}$ of the solution?

Sima Sarker

Numerade Educator

Problem 122

Tellurium, in the same family as sulfur, forms an acid analogous to sulfuric acid and called telluric acid. It exists, however, as $\mathrm{H}_{6} \mathrm{TeO}_{6}$ (which can be understood as the formula $\left.\mathrm{H}_{2} \mathrm{TeO}_{4}+2 \mathrm{H}_{2} \mathrm{O}\right) .$ It is a diprotic acid with $K_{\mathrm{a}_{1}}=2 \times 10^{-8}$ and $K_{\mathrm{a}_{2}}=1 \times 10^{-11} \cdot$ Calculate the concentrations of $\mathrm{H}^{+}, \mathrm{H}_{5} \mathrm{TeO}_{6}^{-},$ and $\mathrm{H}_{4} \mathrm{TeO}_{6}^{2-}$ in a $0.25 \mathrm{M}$ solution of $\mathrm{H}_{6} \mathrm{TeO}_{6}$. What is the $\mathrm{pH}$ of the solution?

David Collins

Numerade Educator

Problem 123

Calculate the concentrations of all of the solute species involved in the equilibria in a $2.0 \mathrm{M}$ solution of $\mathrm{H}_{3} \mathrm{PO}_{4} \cdot$ Calculate the $\mathrm{pH}$ of the solution.

David Collins

Numerade Educator

Problem 124

What is the $\mathrm{pH}$ of a $0.25 \mathrm{M}$ solution of arsenic acid, $\mathrm{H}_{3} \mathrm{As} \mathrm{O}_{4} ?$ In this solution, what are the concentrations of $\mathrm{H}_{2} \mathrm{AsO}_{4}^{-}$ and $\mathrm{HAsO}_{4}^{2-} ?$

David Collins

Numerade Educator

Problem 125

Phosphorous acid, $\mathrm{H}_{3} \mathrm{PO}_{3},$ is actually a diprotic acid for which $K_{a}=5.0 \times 10^{-2}$ and $K_{a}=2.0 \times 10^{-7} .$ What are the values of $\left[\mathrm{H}^{+}\right],\left[\mathrm{H}_{2} \mathrm{PO}_{3}^{-}\right],$ and $\left[\mathrm{HPO}_{3}^{2-}\right]$ in a $1.0 \mathrm{M}$ solution of $\mathrm{H}_{3} \mathrm{PO}_{3}$ ? What is the $\mathrm{pH}$ of the solution?

David Collins

Numerade Educator

Problem 126

What is the $\mathrm{pH}$ of a $0.20 \mathrm{M}$ solution of oxalic acid, $\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} ?$

David Collins

Numerade Educator

Problem 127

Calculate the $\mathrm{pH}$ of $0.24 \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{3}$. What are the concentrations of all ions and $\mathrm{H}_{2} \mathrm{SO}_{3}$ in the solution?

David Collins

Numerade Educator

Problem 128

Calculate the pH of $0.33 \mathrm{MK}_{2} \mathrm{CO}_{3}$. What are the concentrations of all ions and $\mathrm{H}_{2} \mathrm{CO}_{3}$ in the solution?

David Collins

Numerade Educator

Problem 129

Sodium citrate, $\mathrm{Na}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}$, is used as an anticoagulant in the collection of blood. What is the $\mathrm{pH}$ of a $0.10 M$ solution of this salt?

David Collins

Numerade Educator

Problem 130

What is the $\mathrm{pH}$ of a $0.25 \mathrm{M}$ solution of sodium oxalate, $\mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4} ?$

David Collins

Numerade Educator

Problem 131

What is the $\mathrm{pH}$ of a $0.50 \mathrm{M}$ solution of $\mathrm{Na}_{3} \mathrm{PO}_{4} ? \mathrm{In}$ this solution, what are the concentrations of $\mathrm{HPO}_{4}^{2-}$, $\mathrm{H}_{2} \mathrm{PO}_{4}^{-},$ and $\mathrm{H}_{3} \mathrm{PO}_{4} ?$

David Collins

Numerade Educator

Problem 132

The $\mathrm{pH}$ of a $0.10 \mathrm{M} \mathrm{Na}_{2} \mathrm{CO}_{3}$ solution is adjusted to 12.00 using a strong base. What is the concentration of $\mathrm{HCO}_{3}^{-}$ in this solution?

David Collins

Numerade Educator

Problem 133

What is the $\mathrm{pH}$ of a solution prepared by mixing $25.0 \mathrm{~mL}$ of $0.180 \mathrm{M} \mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ with $40.0 \mathrm{~mL}$ of $0.250 \mathrm{M} \mathrm{NaOH} ?$

Sima Sarker

Numerade Educator

Problem 134

What is the $\mathrm{pH}$ of a solution prepared by mixing exactly $25.0 \mathrm{~mL}$ of $0.200 \mathrm{M} \mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ with $15.0 \mathrm{~mL}$ of $0.400 \mathrm{M} \mathrm{KOH}$ ?

David Collins

Numerade Educator

Problem 135

When $50.0 \mathrm{~mL}$ of $0.050 \mathrm{M}$ formic acid, $\mathrm{HCHO}_{2}$, is titrated with $0.050 M$ sodium hydroxide, what is the $\mathrm{pH}$ at the equivalence point? (Be sure to take into account the change in volume during the titration.) Select a good indicator for this titration from Table 16.7 .

David Collins

Numerade Educator

Problem 136

When $25 \mathrm{~mL}$ of $0.12 \mathrm{M}$ aqueous ammonia is titrated with $0.12 \mathrm{M}$ hydrobromic acid, what is the $\mathrm{pH}$ at the equivalence point? Select a good indicator for this titration from Table 16.7 .

David Collins

Numerade Educator

Problem 137

For the titration of $75.00 \mathrm{~mL}$ of $0.1000 \mathrm{M}$ acetic acid with $0.1000 \mathrm{M} \mathrm{NaOH}$, calculate the $\mathrm{pH}$ (a) before the addition of any $\mathrm{NaOH}$ solution, (b) after $25.00 \mathrm{~mL}$ of the base has been added, (c) after half of the $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ has been neutralized, and (d) at the equivalence point.

David Collins

Numerade Educator

Problem 138

For the titration of $50.00 \mathrm{~mL}$ of $0.1000 \mathrm{M}$ ammonia with $0.1000 \mathrm{M} \mathrm{HCl}$, calculate the $\mathrm{pH}$ (a) before the addition of any HCl solution, (b) after $20.00 \mathrm{~mL}$ of the acid has been added, (c) after half of the $\mathrm{NH}_{3}$ has been neutralized, and (d) at the equivalence point.

David Collins

Numerade Educator

Problem 139

Calculate the percentage ionization of acetic acid in solutions having concentrations of $1.0 \mathrm{M}, 0.10 \mathrm{M}$, and $0.010 \mathrm{M}$. How does the percentage ionization of a weak acid change as the acid becomes more dilute?

David Collins

Numerade Educator

Problem 140

What is the $\mathrm{pH}$ of a solution that is $0.100 \mathrm{M}$ in $\mathrm{HCl}$ and also $0.125 \mathrm{M}$ in $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ ? What is the concentration of acetate ion in this solution?

David Collins

Numerade Educator

Problem 141

A solution is prepared by mixing $325 \mathrm{~mL}$ of $0.500 \mathrm{M}$ $\mathrm{NH}_{3}$ and $175 \mathrm{~mL}$ of $0.500 \mathrm{M} \mathrm{HCl}$. Assuming that the volumes are additive, what is the $\mathrm{pH}$ of the resulting mixture?

Sima Sarker

Numerade Educator

Problem 142

A solution is prepared by dissolving $15.0 \mathrm{~g}$ of pure $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ and $25.0 \mathrm{~g}$ of $\mathrm{NaC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ in $775 \mathrm{~mL}$ of solution (the final volume). (a) What is the $\mathrm{pH}$ of the solution? (b) What would the $\mathrm{pH}$ of the solution be if $25.0 \mathrm{~mL}$ of $0.250 \mathrm{M} \mathrm{NaOH}$ were added? (c) What would the $\mathrm{pH}$ be if $25.0 \mathrm{~mL}$ of $0.40 \mathrm{M} \mathrm{HCl}$ were added to the original $775 \mathrm{~mL}$ of buffer solution?

David Collins

Numerade Educator

Problem 143

For an experiment involving what happens to the growth of a particular fungus in a slightly acidic medium, a biochemist needs $255 \mathrm{~mL}$ of an acetate buffer with a $\mathrm{pH}$ of 5.12. The buffer solution has to be able to hold the $\mathrm{pH}$ to within $\pm 0.10 \mathrm{pH}$ unit of 5.12 even if $0.0100 \mathrm{~mol}$ of $\mathrm{NaOH}$ or $0.0100 \mathrm{~mol}$ of $\mathrm{HCl}$ enters the solution.
(a) What is the minimum number of grams of acetic acid and of sodium acetate dihydrate that must be used to prepare the buffer?
(b) Describe the buffer by giving its molarity in acetic acid and its molarity in sodium acetate.
(c) What is the $\mathrm{pH}$ of an unbuffered solution made by adding $0.0100 \mathrm{~mol}$ of $\mathrm{NaOH}$ to $255 \mathrm{~mL}$ of pure water?
(d) What is the $\mathrm{pH}$ of an unbuffered solution made by adding 0.0100 mol of HCl to 255 mL of pure water?

David Collins

Numerade Educator

Problem 144

Predict whether the $\mathrm{pH}$ of $0.120 \mathrm{M} \mathrm{NH}_{4} \mathrm{CN}$ is greater than, less than, or equal to 7.00 . Give your reasons.

Sima Sarker

Numerade Educator

Problem 145

What is the $\mathrm{pH}$ of a $4.5 \times 10^{-2} \mathrm{M}$ solution of ammonium acetate, $\mathrm{NH}_{4} \mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2} ?$

David Collins

Numerade Educator

Problem 146

How many milliliters of ammonia gas measured at $25.2^{\circ} \mathrm{C}$ and 745 torr must be dissolved in $0.250 \mathrm{~L}$ of $0.050 \mathrm{M} \mathrm{HNO}_{3}$ to give a solution with a $\mathrm{pH}$ of $9.26 ?$

David Collins

Numerade Educator

Problem 147

$\mathrm{HClO}_{4}$ is a stronger proton donor than $\mathrm{HNO}_{3}$, but in water both acids appear to be of equal strength; they are both $100 \%$ ionized. Why is this so? What solvent property would be necessary in order to distinguish between the acidities of these two Brønsted acids?

David Collins

Numerade Educator

Problem 148

The hydrogen sulfate ion, $\mathrm{HSO}_{4}^{-},$ is a moderately strong Brønsted acid with a $K_{\mathrm{a}}$ of $1.2 \times 10^{-2}$
(a) Write the chemical equation for the ionization of the acid and give the appropriate $K_{\mathrm{a}}$ expression.
(b) What is the value of $\left[\mathrm{H}^{+}\right]$ in $0.010 \mathrm{M} \mathrm{HSO}_{4}-$ (furnished by the salt, $\mathrm{NaHSO}_{4}$ )? Do NOT make simplifying assumptions; use the quadratic equation.
(c) What is the calculated $\left[\mathrm{H}^{+}\right]$ in $0.010 \mathrm{M} \mathrm{HSO}_{4}^{-},$ obtained by using the usual simplifying assumption?
(d) How much error is introduced by incorrectly using the simplifying assumption?

David Collins

Numerade Educator

Problem 149

Some people who take megadoses of ascorbic acid will drink a solution containing as much as $6.0 \mathrm{~g}$ of ascorbic acid dissolved in a glass of water. Assuming the volume to be $0.250 \mathrm{~L},$ calculate the $\mathrm{pH}$ of this solution.

David Collins

Numerade Educator

Problem 150

For the titration of $25.00 \mathrm{~mL}$ of $0.1000 \mathrm{M} \mathrm{HCl}$ with $0.1000 \mathrm{M} \mathrm{NaOH},$ calculate the $\mathrm{pH}$ of the reaction mixture after each of the following total volumes of base have been added to the original solution. (Remember to take into account the change in total volume.) Construct a graph showing the titration curve for this experiment.
(d) $24.99 \mathrm{~mL}$
(g) $25.10 \mathrm{~mL}$
(b) $10.00 \mathrm{~mL}$
(e) $25.00 \mathrm{~mL}$
(h) $26.00 \mathrm{~mL}$
(c) $24.90 \mathrm{~mL}$
(f) $25.01 \mathrm{~mL}$
(i) $50.00 \mathrm{~mL}$

David Collins

Numerade Educator

Problem 151

Below is a diagram illustrating a mixture $\mathrm{HF}$ and $\mathrm{F}^{-}$ in an aqueous solution. For this mixture, does $\mathrm{pH}$ equal $\mathrm{p} K_{\mathrm{a}}$ for HF? Explain. Describe how the number of $\mathrm{HF}$ molecules and $\mathrm{F}^{-}$ ions will change after three $\mathrm{OH}^{-}$ ions are added. How will the number of $\mathrm{HF}$ and $\mathrm{F}^{-}$ change if two $\mathrm{H}^{+}$ ions are added? Explain your answers by using chemical equations.

David Collins

Numerade Educator

Problem 152

How many milliliters of $0.10 \mathrm{M} \mathrm{NaOH}$ must be added to $0.200 \mathrm{~L}$ of $0.010 \mathrm{M} \mathrm{HCl}$ to give a mixture with a $\mathrm{pH}$ of $3.00 ?$

David Collins

Numerade Educator

Problem 153

Milk of magnesia is a suspension of magnesium hydroxide in water. Although $\mathrm{Mg}(\mathrm{OH})_{2}$ is relatively insoluble, a small amount does dissolve in the water, which makes the mixture slightly basic and gives it a $\mathrm{pH}$ of $10.08 .$ How many grams of $\mathrm{Mg}(\mathrm{OH})_{2}$ are actually dissolved in 2.0 tablespoons of milk of magnesia?

David Collins

Numerade Educator

Problem 154

How many milliliters of $0.0100 \mathrm{M} \mathrm{KOH}$ are needed to completely neutralize the $\mathrm{HCl}$ in $325 \mathrm{~mL}$ of a hydrochloric acid solution that has a $\mathrm{pH}$ of 2.25 ?

Sima Sarker

Numerade Educator

Problem 155

It was found that $25.20 \mathrm{~mL}$ of an $\mathrm{HNO}_{3}$ solution are needed to react completely with $30.0 \mathrm{~mL}$ of a $\mathrm{LiOH}$ solution that has a $\mathrm{pH}$ of $12.05 .$ What is the molarity of the $\mathrm{HNO}_{3}$ solution?

Sima Sarker

Numerade Educator

Problem 156

Suppose $38.0 \mathrm{~mL}$ of $0.000200 \mathrm{M} \mathrm{HCl}$ is added to $40.0 \mathrm{~mL}$ of $0.000180 \mathrm{M} \mathrm{NaOH}$. What will be the $\mathrm{pH}$ of the final mixture?

David Collins

Numerade Educator

Problem 157

Suppose $10.0 \mathrm{~mL}$ of $\mathrm{HCl}$ gas at $25^{\circ} \mathrm{C}$ and 734 torr is bubbled into $257 \mathrm{~mL}$ of pure water. What will be the $\mathrm{pH}$ of the resulting solution, assuming all the $\mathrm{HCl}$ dissolves in the water?

David Collins

Numerade Educator

Problem 158

Suppose the HCl described in the preceding problem is bubbled into $20.00 \mathrm{~L}$ of a solution of $\mathrm{NaOH}$ that has a $\mathrm{pH}$ of $10.50 .$ What will the $\mathrm{pH}$ of the resulting solution be?

David Collins

Numerade Educator

Problem 159

What is the approximate freezing point of a $0.50 \mathrm{M}$ solution of dichloroacetic acid, $\mathrm{HC}_{2} \mathrm{HO}_{2} \mathrm{Cl}_{2}\left(K_{\mathrm{a}}=\right.$ $5.0 \times 10^{-2}$ )? Assume the density of the solution is $1.0 \mathrm{~g} / \mathrm{mL}$

David Collins

Numerade Educator

Problem 160

What happens to the $\mathrm{pH}$ of a solution as it is heated? Does that mean that the autoionization of water is exothermic or endothermic?

David Collins

Numerade Educator

Problem 161

Can the $\mathrm{pH}$ of a solution ever have a negative value? Give an example of a situation where the $\mathrm{pH}$ has a negative value.

David Collins

Numerade Educator

Problem 162

In simplifying our calculations, we were satisfied with a maximum error of $5 \%$ in the concentration of hydronium ions when we compare the value calculated from the quadratic formula to the value obtained using $\operatorname{sim}-$ plifying assumptions. What does an error of $5 \%$ in hydrogen ion concentration mean in terms of $\mathrm{pH}$ ? Is the $\mathrm{pH}$ error the same for a $1.0 \times 10^{-3} \mathrm{M} \mathrm{H}^{+}$ solution as it is for a $5.0 \times 10^{-6} \mathrm{M}$ solution?

David Collins

Numerade Educator

Problem 163

In the 1950 s it was discovered that lakes in the northeastern United States had declining fish populations due to increased acidity. In order to address the problem of lake acidification, make a list of what you need to know in order to start addressing the problem.

David Collins

Numerade Educator

Problem 164

Where are buffers found in everyday consumer products? Propose reasons why a manufacturer would use a buffer in a given product of your choice.

David Collins

Numerade Educator

Problem 165

Why must the acid used for a buffer have a $\mathrm{p} K_{\mathrm{a}}$ within one $\mathrm{pH}$ unit of the $\mathrm{pH}$ of the buffer? What happens if that condition is not met?

David Collins

Numerade Educator

Problem 166

What conjugate acid-base pairs are used to buffer (a) over-the-counter drugs, (b) foods (c) cosmetics, and (d) shampoos?

Crystal Wang

Numerade Educator

Problem 167

Your blood at $37^{\circ} \mathrm{C}$ needs to be maintained within a narrow $\mathrm{pH}$ range of 7.35 to 7.45 to maintain optimal health. What possible conjugate acid-base pairs are present in blood that can buffer the blood and keep it within this range?

David Collins

Numerade Educator

Problem 168

Develop a list of the uses of phosphoric acid in various consumer products.

David Collins

Numerade Educator

Problem 169

What would our $\mathrm{pH}$ scale look like if Arrhenius decided that $\mathrm{pH}=-\ln \left[\mathrm{H}^{+}\right] ?$ What would the $\mathrm{pH}$ of a neutral solution be?

David Collins

Numerade Educator