Chemistry

Raymond Chang, Jason Overby

Chapter 16

Acid-Base Equilibria and Solubility Equilibria - all with Video Answers

Educators

+ 3 more educators

Chapter Questions

Problem 1

Use Le Châtelier's principle to explain how the common ion effect affects the $\mathrm{pH}$ of a solution.

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 2

Describe the effect on $\mathrm{pH}$ (increase, decrease, or no change) that results from each of the following additions: (a) potassium acetate to an acetic acid solution; (b) ammonium nitrate to an ammonia solution;
(c) sodium formate (HCOONa) to a formic acid (HCOOH) solution; (d) potassium chloride to a hydrochloric acid solution; (e) barium iodide to a hydroiodic acid solution.

Dyani Melgarejo

Dyani Melgarejo

Numerade Educator

Problem 3

Define $\mathrm{p} K_{\text {a }}$ for a weak acid. What is the relationship between the value of the $\mathrm{p} K_{\mathrm{a}}$ and the strength of the acid? Do the same for a weak base.

Sneha Hoysala

Duquesne University

Problem 4

The $\mathrm{p} K_{2} \mathrm{~s}$ of two monoprotic acids $\mathrm{HA}$ and $\mathrm{HB}$ are 5.9 and $8.1,$ respectively. Which of the two is the stronger acid?

David Collins

Numerade Educator

Problem 5

Determine the $\mathrm{pH}$ of (a) a $0.40 \mathrm{MCH}_{3} \mathrm{COOH}$ solution, (b) a solution that is $0.40 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}$ and $0.20 \mathrm{M} \mathrm{CH}_{3} \mathrm{COONa} .$

Aadit Sharma

Numerade Educator

Problem 6

Determine the $\mathrm{pH}$ of (a) a $0.20 \mathrm{M} \mathrm{NH}_{3}$ solution,
(b) a solution that is $0.20 M$ in $\mathrm{NH}_{3}$ and $0.30 \mathrm{M}$ $\mathrm{NH}_{4} \mathrm{Cl}$

Dyani Melgarejo

Dyani Melgarejo

Numerade Educator

Problem 7

What is a buffer solution? What constitutes a buffer solution?

Sneha Hoysala

Duquesne University

Problem 8

Which of the following has the greatest buffer capacity: (a) $0.40 \mathrm{M} \mathrm{CH}_{3} \mathrm{COONa} / 0.20 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}$
$\begin{array}{llll}\text { (b) } 0.40 & M \text { CH }_{3} \text { COONa/0.60 } & \text { M CH }_{3} \text { COOH. }\end{array}$
(c) $0.30 \mathrm{M} \mathrm{CH}_{3} \mathrm{COONa} / 0.60 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}^{2}$

David Collins

Numerade Educator

Problem 9

Which of the following solutions can act as a buffer.
(a) $\mathrm{KCl} / \mathrm{HCl}$,
(b) $\mathrm{KHSO}_{4} / \mathrm{H}_{2} \mathrm{SO}_{4}$
(c) $\mathrm{Na}_{2} \mathrm{HPO}_{4} /$
$\mathrm{NaH}_{2} \mathrm{PO}_{4}$
(d) $\mathrm{KNO}_{2} / \mathrm{HNO}_{2} ?$

Aashna Calidas

Numerade Educator

Problem 10

Which of the following solutions can act as a buffer:
(a) $\mathrm{KCN} / \mathrm{HCN}$
(b) $\mathrm{Na}_{2} \mathrm{SO}_{4} / \mathrm{NaHSO}_{4}$
(c) $\mathrm{NH}_{3} /$
$\mathrm{NH}_{4} \mathrm{NO}_{3}$, (d) $\mathrm{Nal} / \mathrm{HI}^{2}$

David Collins

Numerade Educator

Problem 11

Calculate the $\mathrm{pH}$ of the buffer system made up of
$0.15 M \mathrm{NH}_{3} / 0.35 \mathrm{M} \mathrm{NH}_{4} \mathrm{Cl}$

Aashna Calidas

Numerade Educator

Problem 12

Calculate the $\mathrm{pH}$ of the following two buffer solutions: (a) $2.0 \mathrm{M} \mathrm{CH}_{3} \mathrm{COONa} / 2.0 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}$,
(b) $0.20 \mathrm{M} \mathrm{CH}_{3} \mathrm{COONa} / 0.20 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH} .$ Which
is the more effective buffer? Why?

Aashna Calidas

Numerade Educator

Problem 13

The $\mathrm{pH}$ of a bicarbonate-carbonic acid buffer is $8.00 .$ Calculate the ratio of the concentration of carbonic acid $\left(\mathrm{H}_{2} \mathrm{CO}_{3}\right)$ to that of the bicarbonate ion $\left(\mathrm{HCO}_{3}^{-}\right)$

Sneha Hoysala

Duquesne University

Problem 14

What is the pH of the buffer $0.10 \mathrm{M} \mathrm{Na}_{2} \mathrm{HPO}_{4} /$
$0.15 M \mathrm{KH}_{2} \mathrm{PO}_{4} ?$

Nicole Krahulik

Nicole Krahulik

Numerade Educator

Problem 15

The $\mathrm{pH}$ of a sodium acetate-acetic acid buffer is 4.50. Calculate the ratio $\left.\left[\mathrm{CH}_{3} \mathrm{COO}^{-}\right] / \mathrm{CH}_{3} \mathrm{COOH}\right]$.

Sneha Hoysala

Duquesne University

Problem 16

The $\mathrm{pH}$ of blood plasma is 7.40 . Assuming the principal buffer system is $\mathrm{HCO}_{3}^{-} / \mathrm{H}_{2} \mathrm{CO}_{2},$ calculate the ratio $\left[\mathrm{HCO}_{3}^{-}\right] /\left[\mathrm{H}_{2} \mathrm{CO}_{3}\right] .$ Is this buffer more effective against an added acid or an added base?

David Collins

Numerade Educator

Problem 17

Calculate the $\mathrm{pH}$ of the $0.20 \mathrm{M} \mathrm{NH}_{3} / 0.20 \mathrm{M} \mathrm{NH}_{4} \mathrm{Cl}$
buffer. What is the pH of the buffer after the addition of $10.0 \mathrm{~mL}$ of $0.10 \mathrm{M} \mathrm{HCl}$ to $65.0 \mathrm{~mL}$ of the buffer?

Sneha Hoysala

Duquesne University

Problem 18

Calculate the $\mathrm{pH}$ of $1.00 \mathrm{~L}$ of the buffer $1.00 \mathrm{M}$ $\mathrm{CH}_{3} \mathrm{COONa} / 1.00 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}$ before and after the
addition of (a) $0.080 \mathrm{~mol} \mathrm{NaOH},$ (b) $0.12 \mathrm{~mol} \mathrm{HCl}$.
(Assume that there is no change in volume.)

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 19

A diprotic acid, $\mathrm{H}_{2} \mathrm{~A},$ has the following ionization constants: $K_{a_{1}}=1.1 \times 10^{-3}$ and $K_{\mathrm{a}_{2}}=2.5 \times 10^{-6} . \mathrm{In}$
order to make up a buffer solution of $\mathrm{pH} 5.80$, which combination would you choose: NaHA/ $\mathrm{H}_{2} \mathrm{~A}$ or $\mathrm{Na}_{2} \mathrm{~A} / \mathrm{NaHA} ?$

Aadit Sharma

Numerade Educator

Problem 20

A student is asked to prepare a buffer solution at $\mathrm{pH}=$ $8.60,$ using one of the following weak acids: HA $\left(K_{a}=2.7 \times 10^{-3}\right), \mathrm{HB}\left(K_{2}=4.4 \times 10^{-6}\right), \mathrm{HC}\left(K_{\mathrm{a}}=\right.$
$2.6 \times 10^{-9}$ ). Which acid should she choose? Why?

Nicole Krahulik

Nicole Krahulik

Numerade Educator

Problem 21

The diagrams (a)-(d) contain one or more of the compounds $\mathrm{H}_{2} \mathrm{~A}, \mathrm{NaHA},$ and $\mathrm{Na}_{2} \mathrm{~A},$ where $\mathrm{H}_{2} \mathrm{~A}$ is a
weak diprotic acid. (1) Which of the solutions can act as buffer solutions? (2) Which solution is the most effective buffer solution? (Water molecules and $\mathrm{Na}^{+}$ ions have been omitted for clarity.)

David Collins

Numerade Educator

Problem 22

The diagrams shown here represent solutions containing a weak acid HA $\left(\mathrm{p} K_{\mathrm{a}}=5.00\right)$ and its sodium salt NaA. (1) Calculate the pH of the solutions.
(2) What is the pH after the addition of $0.1 \mathrm{~mol} \mathrm{H}^{+}$ ions to solution (a)? (3) What is the pH after the addition of $0.1 \mathrm{~mol} \mathrm{OH}^{-}$ ions to solution (d)? Treat each sphere as 0.1 mol.

Manik Pulyani

Numerade Educator

Problem 23

How much $\mathrm{NaOH}$ (in moles) must be added to $1 \mathrm{~L}$ of a buffer solution that is $1.8 M$ in acetic acid and $1.2 M$ in sodium acetate to result in a buffer solution of $\mathrm{pH} 5.22 ?$ Assume volume to remain constant.

David Collins

Numerade Educator

Problem 24

How much HCl (in moles) must be added to 1 L of a buffer solution that is $0.84 M$ in ammonia and $0.96 M$ in ammonium chloride to result in a buffer solution of $\mathrm{pH} 8.56$ ? Assume volume to remain constant.

Prashant Bana

Numerade Educator

Problem 25

Briefly describe what happens in an acid-base titration.

Sneha Hoysala

Duquesne University

Problem 26

Sketch titration curves for the following acid-base titrations: (a) $\mathrm{HCl}$ versus $\mathrm{NaOH},$ (b) $\mathrm{HCl}$ versus $\mathrm{CH}_{3} \mathrm{NH}_{2},$ (c) $\mathrm{CH}_{3} \mathrm{COOH}$ versus $\mathrm{NaOH}$. In each
case, the base is added to the acid in an Erlenmeyer flask. Your graphs should show $\mathrm{pH}$ on the $y$ axis and volume of base added on the $x$ axis.

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 27

A 0.2688 -g sample of a monoprotic acid neutralizes $16.4 \mathrm{~mL}$ of $0.08133 \mathrm{M}$ KOH solution. Calculate the
molar mass of the acid.

Sneha Hoysala

Duquesne University

Problem 28

A $5.00-\mathrm{g}$ quantity of a diprotic acid was dissolved in water and made up to exactly $250 \mathrm{~mL}$. Calculate the molar mass of the acid if $25.0 \mathrm{~mL}$ of this solution required $11.1 \mathrm{~mL}$ of $1.00 \mathrm{M}$ KOH for neutralization. Assume that both protons of the acid were titrated.

Aadit Sharma

Numerade Educator

Problem 29

In a titration experiment, $12.5 \mathrm{~mL}$ of $0.500 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$
neutralize $50.0 \mathrm{~mL}$ of $\mathrm{NaOH}$. What is the concentration of the $\mathrm{NaOH}$ solution?

Sneha Hoysala

Duquesne University

Problem 30

In a titration experiment, $20.4 \mathrm{~mL}$ of $0.883 \mathrm{M}$ HCOOH neutralize $19.3 \mathrm{~mL}$ of $\mathrm{Ba}(\mathrm{OH})_{2} .$ What is the concentration of the $\mathrm{Ba}(\mathrm{OH})_{2}$ solution?

Prashant Bana

Numerade Educator

Problem 31

A 0.1276 -g sample of an unknown monoprotic acid was dissolved in $25.0 \mathrm{~mL}$ of water and titrated with $0.0633 \mathrm{M} \mathrm{NaOH}$ solution. The volume of base required to bring the solution to the equivalence point was $18.4 \mathrm{~mL}$. (a) Calculate the molar mass of the acid. (b) After $10.0 \mathrm{~mL}$ of base had been added during the titration, the $\mathrm{pH}$ was determined to be 5.87 . What is the $K_{\mathrm{a}}$ of the unknown acid?

David Collins

Numerade Educator

Problem 32

A solution is made by mixing $5.00 \times 10^{2} \mathrm{~mL}$ of $0.167 M \mathrm{NaOH}$ with $5.00 \times 10^{2} \mathrm{~mL}$ of $0.100 \mathrm{M}$
$\mathrm{CH}_{3} \mathrm{COOH} .$ Calculate the equilibrium concentrations of $\mathrm{H}^{+}, \mathrm{CH}_{3} \mathrm{COOH}, \mathrm{CH}_{3} \mathrm{COO}^{-}, \mathrm{OH}^{-}$
and $\mathrm{Na}^{+}$

David Collins

Numerade Educator

Problem 33

Calculate the $\mathrm{pH}$ at the equivalence point for the following titration: $0.20 \mathrm{M} \mathrm{HCl}$ versus $0.20 \mathrm{M}$ methylamine $\left(\mathrm{CH}_{3} \mathrm{NH}_{2}\right)$. (See Table 15.4.)

Iryna Ivaniuk

Numerade Educator

Problem 34

Calculate the $\mathrm{pH}$ at the equivalence point for the following titration: $0.10 \mathrm{M} \mathrm{HCOOH}$ versus $0.10 \mathrm{M}$ NaOH.

David Collins

Numerade Educator

Problem 35

A $25.0-\mathrm{mL}$ solution of $0.100 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}$ is ti-
trated with a $0.200 \mathrm{M}$ KOH solution. Calculate the $\mathrm{pH}$ after the following additions of the KOH solution:
(a) $0.0 \mathrm{~mL},$
(b) $5.0 \mathrm{~mL},$
(c) $10.0 \mathrm{~mL}$,
(d) $12.5 \mathrm{~mL}$
(e) $15.0 \mathrm{~mL}$.

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 36

A $10.0-\mathrm{mL}$ solution of $0.300 \mathrm{M} \mathrm{NH}_{3}$ is titrated with a $0.100 M \mathrm{HCl}$ solution. Calculate the $\mathrm{pH}$ after the following additions of the $\mathrm{HCl}$ solution:
(a) $0.0 \mathrm{~mL},$
(b) $10.0 \mathrm{~mL}$
(c) $20.0 \mathrm{~mL}$
(d) $30.0 \mathrm{~mL}$
(e) $40.0 \mathrm{~mL}$

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 37

The diagrams shown here represent solutions at different stages in the titration of a weak acid HA with $\mathrm{NaOH} .$ Identify the solution that corresponds to
(1) the initial stage before the addition of $\mathrm{NaOH}$,
(2) halfway to the equivalence point, ( 3 ) the equivalence point, (4) beyond the equivalence point. Is the $\mathrm{pH}$ greater than, less than, or equal to 7 at the equivalence point? Water molecules and $\mathrm{Na}^{+}$ ions have been omitted for clarity.

Iryna Ivaniuk

Numerade Educator

Problem 38

The diagrams shown here represent solutions at various stages in the titration of a weak base $\mathrm{B}$ (such as $\mathrm{NH}_{3}$ ) with $\mathrm{HCl}$. Identify the solution that corresponds to (1) the initial stage before the addition of $\mathrm{HCl},(2)$ halfway to the equivalence point, (3) the equivalence point, (4) beyond the equivalence point. Is the $\mathrm{pH}$ greater than, less than, or equal to 7 at the equivalence point? Water molecules and $\mathrm{Cl}^{-}$ ions have been omitted for clarity.

Aadit Sharma

Numerade Educator

Problem 39

A $0.054 M \mathrm{HNO}_{2}$ solution is titrated with a $\mathrm{KOH}$ solution. What is $\left[\mathrm{H}^{+}\right]$ at half way to the equivalence point?

Iryna Ivaniuk

Numerade Educator

Problem 40

A student titrates an unknown monoprotic acid with a $\mathrm{NaOH}$ solution from a buret. After the addition of $12.35 \mathrm{~mL}$ of $\mathrm{NaOH},$ the $\mathrm{pH}$ of the solution read 5.22. The equivalence point is reached at $24.70 \mathrm{~mL}$ of $\mathrm{NaOH}$. What is the $K_{\mathrm{a}}$ of the acid?

Prashant Bana

Numerade Educator

Problem 41

Explain how an acid-base indicator works in a titration. What are the criteria for choosing an indicator for a particular acid-base titration?

Iryna Ivaniuk

Numerade Educator

Problem 42

The amount of indicator used in an acid-base titration must be small. Why?

Aashna Calidas

Numerade Educator

Problem 43

Referring to Table 16.1 , specify which indicator or indicators you would use for the following titrations:
(a) HCOOH versus $\mathrm{NaOH}$,
(b) HCl versus $\mathrm{KOH}$
(c) $\mathrm{HNO}_{3}$ versus $\mathrm{CH}_{3} \mathrm{NH}_{2}$.

Iryna Ivaniuk

Numerade Educator

Problem 44

A student carried out an acid-base titration by adding $\mathrm{NaOH}$ solution from a buret to an Erlenmeyer flask containing HCl solution and using phenolphthalein as indicator. At the equivalence point, she observed a faint reddish-pink color. However, after a few minutes, the solution gradually turned colorless. What do you suppose happened?

Prashant Bana

Numerade Educator

Problem 45

The ionization constant $K_{\mathrm{a}}$ of an indicator $\mathrm{HIn}$ is $1.0 \times 10^{-6} .$ The color of the nonionized form is red and that of the ionized form is yellow. What is the color of this indicator in a solution whose $\mathrm{pH}$ is $4.00 ?$

Aashna Calidas

Numerade Educator

Problem 46

The $K_{\mathrm{a}}$ of a certain indicator is $2.0 \times 10^{-6} .$ The color of HIn is green and that of In $^{-}$ is red. A few drops of the indicator are added to a HCl solution, which is then titrated against a $\mathrm{NaOH}$ solution. At what $\mathrm{pH}$ will the indicator change color?

Prashant Bana

Numerade Educator

Problem 47

Use BaSO $_{4}$ to distinguish between solubility, molar solubility, and solubility product.

Iryna Ivaniuk

Numerade Educator

Problem 48

Why do we usually not quote the $K_{\mathrm{sp}}$ values for soluble ionic compounds?

Aashna Calidas

Numerade Educator

Problem 49

Write balanced equations and solubility product expressions for the solubility equilibria of the following compounds:
(a) $\mathrm{CuBr}$
(b) $\mathrm{ZnC}_{2} \mathrm{O}_{4}$
(c) $\mathrm{Ag}_{2} \mathrm{CrO}_{4},$
(d) $\mathrm{Hg}_{2} \mathrm{Cl}_{2}$,
(e) $\mathrm{AuCl}_{3}$
(f) $\mathrm{Mn}_{3}\left(\mathrm{PO}_{4}\right)_{2}$

Prashant Bana

Numerade Educator

Problem 50

Write the solubility product expression for the ionic compound $\mathrm{A}_{x} \mathrm{~B}_{y}$

Aashna Calidas

Numerade Educator

Problem 51

How can we predict whether a precipitate will form when two solutions are mixed?

Aashna Calidas

Numerade Educator

Problem 52

Silver chloride has a larger $K_{\mathrm{sp}}$ than silver carbonate (see Table 16.2 ). Does this mean that $\mathrm{AgCl}$ also has a larger molar solubility than $\mathrm{Ag}_{2} \mathrm{CO}_{3} ?$

Prashant Bana

Numerade Educator

Problem 53

Calculate the concentration of ions in the following saturated solutions: (a) [I'] in AgI solution with $\left[\mathrm{Ag}^{+}\right]=9.1 \times 10^{-9} \mathrm{M}$
(b) $\left[\mathrm{Al}^{3+}\right]$ in $\mathrm{Al}(\mathrm{OH})_{3}$ solution with $\left[\mathrm{OH}^{-}\right]=2.9 \times 10^{-9} \mathrm{M}$

David Collins

Numerade Educator

Problem 54

From the solubility data given, calculate the solubility products for the following compounds:
(a) $\mathrm{SrF}_{2}$
$7.3 \times 10^{-2} \mathrm{~g} / \mathrm{L}$
(b) $\mathrm{Ag}_{3} \mathrm{PO}_{4}, 6.7 \times 10^{-3} \mathrm{~g} / \mathrm{L}$

David Collins

Numerade Educator

Problem 55

The molar solubility of $\mathrm{MnCO}_{3}$ is $4.2 \times 10^{-6} \mathrm{M}$. What is $K_{\mathrm{sp}}$ for this compound?

Aashna Calidas

Numerade Educator

Problem 56

The solubility of an ionic compound MX (molar mass $=346 \mathrm{~g}$ ) is $4.63 \times 10^{-3} \mathrm{~g} / \mathrm{L} .$ What is $K_{\mathrm{sp}}$ for
the compound?

Aashna Calidas

Numerade Educator

Problem 57

The solubility of an ionic compound $\mathrm{M}_{2} \mathrm{X}_{3}$ (molar mass $=288 \mathrm{~g}$ ) is $3.6 \times 10^{-17} \mathrm{~g} / \mathrm{L}$. What is $K_{\mathrm{sp}}$ for the compound?

Iryna Ivaniuk

Numerade Educator

Problem 58

Using data from Table $16.2,$ calculate the molar solubility of $\mathrm{CaF}_{2}$.

Aadit Sharma

Numerade Educator

Problem 59

What is the $\mathrm{pH}$ of a saturated zinc hydroxide solution?

Aashna Calidas

Numerade Educator

Problem 60

The $\mathrm{pH}$ of a saturated solution of a metal hydroxide $\mathrm{MOH}$ is 9.68 . Calculate the $K_{\mathrm{sp}}$ for the compound.

Aashna Calidas

Numerade Educator

Problem 61

If $20.0 \mathrm{~mL}$ of $0.10 \mathrm{MBa}\left(\mathrm{NO}_{3}\right)_{2}$ are added to $50.0 \mathrm{~mL}$
of $0.10 \mathrm{M} \mathrm{Na}_{2} \mathrm{CO}_{3},$ will $\mathrm{BaCO}_{3}$ precipitate?

Aashna Calidas

Numerade Educator

Problem 62

A volume of $75 \mathrm{~mL}$ of $0.060 \mathrm{M}$ NaF is mixed with $25 \mathrm{~mL}$ of $0.15 \mathrm{M} \mathrm{Sr}\left(\mathrm{NO}_{3}\right)_{2} .$ Calculate the concentra-
tions in the final solution of $\mathrm{NO}_{3}^{-}, \mathrm{Na}^{+}, \mathrm{Sr}^{2+},$ and $\mathrm{F}^{-}$
$\left(K_{\mathrm{xp}}\right.$ for $\left.\mathrm{SrF}_{2}=2.0 \times 10^{-10}\right)$

David Collins

Numerade Educator

Problem 63

Solid NaI is slowly added to a solution that is $0.010 \mathrm{M}$ in $\mathrm{Cu}^{+}$ and $0.010 \mathrm{M}$ in $\mathrm{Ag}^{+}$
(a) Which compound will begin to precipitate first?
(b) Calculate [Ag $^{+}$ ] when CuI just begins to precipitate.
(c) What percent of $\mathrm{Ag}^{+}$ remains in solution at this point?

Aadit Sharma

Numerade Educator

Problem 64

Find the approximate $\mathrm{pH}$ range suitable for the separation of $\mathrm{Fe}^{3+}$ and $\mathrm{Zn}^{2+}$ ions by precipitation of $\mathrm{Fe}(\mathrm{OH})_{3}$ from a solution that is initially $0.010 \mathrm{M}$ in both $\mathrm{Fe}^{3+}$ and $\mathrm{Zn}^{2+}$. Assume a 99 percent precipitation of $\mathrm{Fe}(\mathrm{OH})_{3}$

David Collins

Numerade Educator

Problem 65

How does the common ion effect influence solubility equilibria? Use Le Châtelier's principle to explain the decrease in solubility of $\mathrm{CaCO}_{3}$ in a $\mathrm{Na}_{2} \mathrm{CO}_{3}$ solution.

Iryna Ivaniuk

Numerade Educator

Problem 66

The molar solubility of $\mathrm{AgCl}$ in $6.5 \times 10^{-3} \mathrm{M} \mathrm{AgNO}_{3}$
is $2.5 \times 10^{-8} M .$ In deriving $K_{\mathrm{sp}}$ from these data, which of the following assumptions are reasonable?
(a) $K_{\mathrm{sp}}$ is the same as solubility.
(b) $K_{\mathrm{sp}}$ of $\mathrm{AgCl}$ is the same in $6.5 \times 10^{-3} \mathrm{M} \mathrm{AgNO}_{3}$
as in pure water.
(c) Solubility of $\mathrm{AgCl}$ is independent of the concentration of $\mathrm{AgNO}_{3}$
(d) $\left[\mathrm{Ag}^{+}\right]$ in solution does not change significantly upon the addition of $\mathrm{AgCl}$ to $6.5 \times 10^{-3} \mathrm{M}$ $\mathrm{AgNO}_{3}$
(e) $\left[\mathrm{Ag}^{+}\right]$ in solution after the addition of $\mathrm{AgCl}$ to $6.5 \times 10^{-3} M \mathrm{AgNO}_{3}$ is the same as it would be in pure water.

Prashant Bana

Numerade Educator

Problem 67

How many grams of $\mathrm{CaCO}_{3}$ will dissolve in $3.0 \times$ $10^{2} \mathrm{~mL}$ of $0.050 \mathrm{M} \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2} ?$

Iryna Ivaniuk

Numerade Educator

Problem 68

The solubility product of $\mathrm{PbBr}_{2}$ is $8.9 \times 10^{-6}$. Determine the molar solubility (a) in pure water, (b) in $0.20 M \mathrm{KBr}$ solution,
(c) in $0.20 \mathrm{M} \mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}$ solution.

Aadit Sharma

Numerade Educator

Problem 69

Calculate the molar solubility of $\mathrm{AgCl}$ in a $1.00-\mathrm{L}$ solution containing $10.0 \mathrm{~g}$ of dissolved $\mathrm{CaCl}_{2}$.

Iryna Ivaniuk

Numerade Educator

Problem 70

Calculate the molar solubility of $\mathrm{BaSO}_{4}$ (a) in water,
(b) in a solution containing $1.0 M \mathrm{SO}_{4}^{2-}$ ions.

Satpal Satpal

Numerade Educator

Problem 71

Which of the following ionic compounds will be more soluble in acid solution than in water:
(a) $\mathrm{BaSO}_{4}$
(b) $\mathrm{PbCl}_{2}$
(c) $\mathrm{Fe}(\mathrm{OH})_{3}$
(d) $\mathrm{CaCO}_{3} ?$

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 72

Which of the following will be more soluble in acid solution than in pure water:
(a) $\mathrm{CuI}$,
(b) $\mathrm{Ag}_{2} \mathrm{SO}_{4}$,
(c) $\mathrm{Zn}(\mathrm{OH})_{2}$
(d) $\mathrm{BaC}_{2} \mathrm{O}_{4}$
(e) $\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2} ?$

Ronald Prasad

Numerade Educator

Problem 73

Compare the molar solubility of $\mathrm{Mg}(\mathrm{OH})_{2}$ in water and in a solution buffered at a pH of 9.0 .

Aashna Calidas

Numerade Educator

Problem 74

Calculate the molar solubility of $\mathrm{Fe}(\mathrm{OH})_{2}$ in a solution buffered at (a) $\mathrm{pH} 8.00,$ (b) $\mathrm{pH} 10.00$.

Aadit Sharma

Numerade Educator

Problem 75

The solubility product of $\mathrm{Mg}(\mathrm{OH})_{2}$ is $1.2 \times 10^{-11}$ What minimum $\mathrm{OH}^{-}$ concentration must be attained
(for example, by adding $\mathrm{NaOH}$ ) to decrease the $\mathrm{Mg}^{2+}$ concentration in a solution of $\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}$ to less than $1.0 \times 10^{-10} M ?$

Iryna Ivaniuk

Numerade Educator

Problem 76

Calculate whether or not a precipitate will form if $2.00 \mathrm{~mL}$ of $0.60 \mathrm{M} \mathrm{NH}_{3}$ are added to $1.0 \mathrm{~L}$ of
$1.0 \times 10^{-3} M \mathrm{FeSO}_{4}$

David Collins

Numerade Educator

Problem 77

Explain the formation of complexes in Table 16.4 in terms of Lewis acid-base theory.

David Collins

Numerade Educator

Problem 78

Give an example to illustrate the general effect of complex ion formation on solubility.

Aashna Calidas

Numerade Educator

Problem 79

If $2.50 \mathrm{~g}$ of $\mathrm{CuSO}_{4}$ are dissolved in $9.0 \times 10^{2} \mathrm{~mL}$ of $0.30 M \mathrm{NH}_{3},$ what are the concentrations of $\mathrm{Cu}^{2+}$ $\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}^{2+},$ and $\mathrm{NH}_{3}$ at equilibrium?

Nicholas Mogoi

Numerade Educator

Problem 80

Calculate the concentrations of $\mathrm{Cd}^{2+}, \mathrm{Cd}(\mathrm{CN})_{4}^{2-}$ and $\mathrm{CN}^{-}$ at equilibrium when $0.50 \mathrm{~g}$ of $\mathrm{Cd}\left(\mathrm{NO}_{3}\right)_{2}$ dissolves in $5.0 \times 10^{2} \mathrm{~mL}$ of $0.50 \mathrm{M} \mathrm{NaCN}$.

Manik Pulyani

Numerade Educator

Problem 81

If $\mathrm{NaOH}$ is added to $0.010 \mathrm{M} \mathrm{Al}^{3+}$, which will be the predominant species at equilibrium: $\mathrm{Al}(\mathrm{OH})_{3}$ or $\mathrm{Al}(\mathrm{OH})_{4}^{-} ?$ The $\mathrm{pH}$ of the solution is $14.00 .\left[K_{\mathrm{f}}\right.$ for
$\left.\mathrm{Al}(\mathrm{OH})_{4}^{-}=2.0 \times 10^{33} .\right]$

Iryna Ivaniuk

Numerade Educator

Problem 82

Calculate the molar solubility of AgI in a $1.0 \mathrm{M} \mathrm{NH}_{3}$ solution.

Aadit Sharma

Numerade Educator

Problem 83

Both $\mathrm{Ag}^{+}$ and $\mathrm{Zn}^{2+}$ form complex ions with $\mathrm{NH}_{3}$. Write balanced equations for the reactions. However, $\mathrm{Zn}(\mathrm{OH})_{2}$ is soluble in $6 \mathrm{M} \mathrm{NaOH},$ and $\mathrm{AgOH}$ is not. Explain.

Prashant Bana

Numerade Educator

Problem 84

Explain, with balanced ionic equations, why
(a) $\mathrm{CuI}_{2}$ dissolves in ammonia solution,
(b) AgBr dissolves in $\mathrm{NaCN}$ solution, (c) $\mathrm{HgCl}_{2}$ dissolves in KCl solution.

Prashant Bana

Numerade Educator

Problem 85

Outline the general procedure of qualitative analysis.

Iryna Ivaniuk

Numerade Educator

Problem 86

Give two examples of metal ions in each group ( 1 through 5 ) in the qualitative analysis scheme.

Prashant Bana

Numerade Educator

Problem 87

In a group 1 analysis, a student obtained a precipitate containing both $\mathrm{AgCl}$ and $\mathrm{PbCl}_{2}$. Suggest one reagent that would enable her to separate $\operatorname{AgCl}(s)$ from $\mathrm{PbCl}_{2}(s)$

Iryna Ivaniuk

Numerade Educator

Problem 88

In a group 1 analysis, a student adds $\mathrm{HCl}$ acid to the unknown solution to make $\left[\mathrm{Cl}^{-}\right]=0.15 M .$ Some $\mathrm{PbCl}_{2}$ precipitates. Calculate the concentration of $\mathrm{Pb}^{2+}$ remaining in solution.

Prashant Bana

Numerade Educator

Problem 89

Both $\mathrm{KCl}$ and $\mathrm{NH}_{4} \mathrm{Cl}$ are white solids. Suggest one reagent that would enable you to distinguish between these two compounds.

Iryna Ivaniuk

Numerade Educator

Problem 90

Describe a simple test that would enable you to distinguish between $\operatorname{AgNO}_{3}(s)$ and $\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(s)$

Prashant Bana

Numerade Educator

Problem 91

To act as an effective buffer, the concentrations of the acid and the conjugate base should not differ by more than a factor of $10,$ that is,
$$
10 \geq \frac{[\text { conjugate base }]}{[\text { acid }]} \geq 0.1
$$
(a) Show that the buffer range-that is, the range of the concentration ratio over which the buffer is effective-is given by $\mathrm{pH}=\mathrm{p} K_{\mathrm{a}} \pm 1$
(b) Calculate the $\mathrm{pH}$ range for the following buffer systems: (i) acetate, (ii) nitrite, (iii) bicarbonate, (iv) phosphate.

David Collins

Numerade Educator

Problem 92

The $p K_{a}$ of the indicator methyl orange is $3.46 .$ Over what pH range does this indicator change from 90 percent HIn to 90 percent In $^{-} ?$

Prashant Bana

Numerade Educator

Problem 93

The iodide impurity in a $4.50-\mathrm{g}$ sample of a metal nitrate is precipitated as silver iodide. If $5.54 \mathrm{~mL}$ of $0.186 M$ AgNO $_{3}$ solution is needed for the precipitation, calculate the mass percent of iodide in the sample.

Iryna Ivaniuk

Numerade Educator

Problem 94

A sodium acetate-acetic acid buffer solution was prepared by adding a $0.020 M \mathrm{HCl}$ solution to $500 \mathrm{~mL}$ of $0.020 \mathrm{M} \mathrm{CH}_{3} \mathrm{COONa}$ and then diluting the mixed solution to $1.0 \mathrm{~L}$. Calculate the original volume of the HCl solution needed to prepare a buffer solution of pH 5.00 .

David Collins

Numerade Educator

Problem 95

Sketch the titration curve of a weak acid versus a strong base like the one shown in Figure $16.5 .$ On your graph indicate the volume of base used at the equivalence point and also at the half-equivalence point- - that is, the point at which half of the acid has been neutralized. Show how you can measure the $\mathrm{pH}$ of the solution at the half-equivalence point. Using Equation (16.4), explain how you can determine the $\mathrm{p} K_{\mathrm{a}}$ of the acid by this procedure.

Aadit Sharma

Numerade Educator

Problem 96

A 200 -mL volume of $\mathrm{NaOH}$ solution was added to $400 \mathrm{~mL}$ of a $2.00 \mathrm{M} \mathrm{HNO}_{2}$ solution. The $\mathrm{pH}$ of the mixed solution was 1.50 units greater than that of the original acid solution. Calculate the molarity of the $\mathrm{NaOH}$ solution.

Manik Pulyani

Numerade Educator

Problem 97

The $p K_{a}$ of butyric acid (HBut) is $4.7 .$ Calculate $K_{b}$ for the butyrate ion (But- ).

Sima Sarker

Numerade Educator

Problem 98

A solution is made by mixing $5.00 \times 10^{2} \mathrm{~mL}$ of
HCOOH. Calculate the equilibrium concentrations of $\mathrm{H}^{+}, \mathrm{HCOOH}, \mathrm{HCOO}^{-}, \mathrm{OH}^{-},$ and $\mathrm{Na}^{+}$

David Collins

Numerade Educator

Problem 99

$\mathrm{Cd}(\mathrm{OH})_{2}$ is an insoluble compound. It dissolves in excess $\mathrm{NaOH}$ in solution. Write a balanced ionic equation for this reaction. What type of reaction is this?

Iryna Ivaniuk

Numerade Educator

Problem 100

A student mixes $50.0 \mathrm{~mL}$ of $1.00 \mathrm{M} \mathrm{Ba}(\mathrm{OH})_{2}$
with $86.4 \mathrm{~mL}$ of $0.494 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4} .$ Calculate the
mass of $\mathrm{BaSO}_{4}$ formed and the $\mathrm{pH}$ of the mixed solution.

Aadit Sharma

Numerade Educator

Problem 101

For which of the following reactions is the equilibrium constant called a solubility product?
$$
\begin{array}{l}
\text { (a) } \mathrm{Zn}(\mathrm{OH})_{2}(s)+2 \mathrm{OH}^{-}(a q) \rightleftharpoons \\
\text { (b) } 3 \mathrm{Ca}^{2+}(a q)+2 \mathrm{PO}_{4}^{3-}(a q) \rightleftharpoons \mathrm{Ca}_{3}(\mathrm{OH})_{4}^{2-}(a q)
\end{array}
$$
(c) $\mathrm{CaCO}_{3}(s)+2 \mathrm{H}^{+}(a q) \rightleftharpoons$
$$
\mathrm{Ca}^{2+}(a q)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{CO}_{2}(g)
$$
(d) $\mathrm{PbI}_{2}(s) \rightleftharpoons \mathrm{Pb}^{2+}(a q)+2 \mathrm{I}^{-}(a q)$

Tom Comey

Numerade Educator

Problem 102

A 2.0-L kettle contains $116 \mathrm{~g}$ of boiler scale $\left(\mathrm{CaCO}_{3}\right) .$ How many times would the kettle have to be completely filled with distilled water to remove all of the deposit?

David Collins

Numerade Educator

Problem 103

Equal volumes of $0.12 M \mathrm{AgNO}_{3}$ and $0.14 \mathrm{M} \mathrm{ZnCl}_{2}$
solution are mixed. Calculate the equilibrium concentrations of $\mathrm{Ag}^{+}, \mathrm{Cl}^{-}, \mathrm{Zn}^{2+},$ and $\mathrm{NO}_{3}^{-}$

Iryna Ivaniuk

Numerade Educator

Problem 104

Calculate the solubility (in $\mathrm{g} / \mathrm{L}$ ) of $\mathrm{Ag}_{2} \mathrm{CO}_{3}$.

Aadit Sharma

Numerade Educator

Problem 105

Find the approximate $\mathrm{pH}$ range suitable for separating $\mathrm{Mg}^{2+}$ and $\mathrm{Zn}^{2+}$ by the precipitation of $\mathrm{Zn}(\mathrm{OH})_{2}$ from a solution that is initially $0.010 M$ in $\mathrm{Mg}^{2+}$ and $\mathrm{Zn}^{2+}$

Iryna Ivaniuk

Numerade Educator

Problem 106

A volume of $25.0 \mathrm{~mL}$ of $0.100 \mathrm{M} \mathrm{HCl}$ is titrated against a $0.100 \mathrm{M} \mathrm{CH}_{3} \mathrm{NH}_{2}$ solution added to it from a buret. Calculate the $\mathrm{pH}$ values of the solution
(a) after $10.0 \mathrm{~mL}$ of $\mathrm{CH}_{3} \mathrm{NH}_{2}$ solution have been added, (b) after $25.0 \mathrm{~mL}$ of $\mathrm{CH}_{3} \mathrm{NH}_{2}$ solution have been added, (c) after $35.0 \mathrm{~mL}$ of $\mathrm{CH}_{3} \mathrm{NH}_{2}$ solution have been added.

Manik Pulyani

Numerade Educator

Problem 107

The molar solubility of $\mathrm{Pb}\left(\mathrm{IO}_{3}\right)_{2}$ in a $0.10 \mathrm{M} \mathrm{NaIO}_{3}$
solution is $2.4 \times 10^{-11} \mathrm{~mol} / \mathrm{L} .$ What is $K_{\mathrm{sp}}$ for $\mathrm{Pb}\left(\mathrm{IO}_{3}\right)_{2} ?$

Iryna Ivaniuk

Numerade Educator

Problem 108

When a KI solution was added to a solution of mercury(II) chloride, a precipitate [mercury(II) iodide] formed. A student plotted the mass of the precipitate versus the volume of the KI solution added and obtained the following graph. Explain the appearance of the graph.

Aadit Sharma

Numerade Educator

Problem 109

Barium is a toxic substance that can seriously impair heart function. For an X ray of the gastrointestinal tract, a patient drinks an aqueous suspension of $20 \mathrm{~g} \mathrm{BaSO}_{4} .$ If this substance were to equilibrate with the $5.0 \mathrm{~L}$ of the blood in the patient's body, what would be $\left[\mathrm{Ba}^{2+}\right]$ ? For a good estimate, we may assume that the temperature is at $25^{\circ} \mathrm{C}$. Why is $\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}$ not chosen for this procedure?

Iryna Ivaniuk

Numerade Educator

Problem 110

The $\mathrm{p} K_{\mathrm{a}}$ of phenolphthalein is $9.10 .$ Over what $\mathrm{pH}$ range does this indicator change from 95 percent HIn to 95 percent $\mathrm{In}^{-} ?$

Prashant Bana

Numerade Educator

Problem 111

Solid NaBr is slowly added to a solution that is $0.010 \mathrm{M}$ in $\mathrm{Cu}^{+}$ and $0.010 \mathrm{M}$ in $\mathrm{Ag}^{+}$. (a) Which compound will begin to precipitate first?
(b) Calculate $\left[\mathrm{Ag}^{+}\right]$ when CuBr just begins to precipitate. (c) What percent of $\mathrm{Ag}^{+}$ remains in solution at this point?

Iryna Ivaniuk

Numerade Educator

Problem 112

Solid NaBr is slowly added to a solution that is $0.010 \mathrm{M}$ in $\mathrm{Cu}^{+}$ and $0.010 \mathrm{M}$ in $\mathrm{Ag}^{+}$. (a) Which compound will begin to precipitate first?
(b) Calculate $\left[\mathrm{Ag}^{+}\right]$ when CuBr just begins to precipitate. (c) What percent of $\mathrm{Ag}^{+}$ remains in solution at this point?

Iryna Ivaniuk

Numerade Educator

Problem 113

Radiochemical techniques are useful in estimating the solubility product of many compounds. In one experiment, $50.0 \mathrm{~mL}$ of a $0.010 \mathrm{M} \mathrm{AgNO}_{3}$ solution containing a silver isotope with a radioactivity of 74,025 counts per min per $\mathrm{mL}$ were mixed with $100 \mathrm{~mL}$ of a $0.030 \mathrm{M} \mathrm{NaIO}_{3}$ solution. The mixed solution was diluted to $500 \mathrm{~mL}$ and filtered to remove all of the AgIO precipitate. The remaining solution was found to have a radioactivity of 44.4 counts per min per $\mathrm{mL}$. What is the $K_{\mathrm{sp}}$ of $\mathrm{AgIO}_{3} ?$

David Collins

Numerade Educator

Problem 114

The molar mass of a certain metal carbonate, $\mathrm{MCO}_{3}$, can be determined by adding an excess of $\mathrm{HCl}$ acid to react with all the carbonate and then "back titrating" the remaining acid with a $\mathrm{NaOH}$ solution.
(a) Write equations for these reactions. (b) In a certain experiment, $18.68 \mathrm{~mL}$ of $5.653 \mathrm{M} \mathrm{HCl}$ were added to a $3.542-\mathrm{g}$ sample of $\mathrm{MCO}_{3}$. The excess HCl required $12.06 \mathrm{~mL}$ of $1.789 \mathrm{M} \mathrm{NaOH}$ for
neutralization. Calculate the molar mass of the carbonate and identify $\mathrm{M}$.

David Collins

Numerade Educator

Problem 115

Acid-base reactions usually go to completion. Confirm this statement by calculating the equilibrium constant for each of the following cases: (a) a strong acid reacting with a strong base; (b) a strong acid reacting with a weak base $\left(\mathrm{NH}_{3}\right) ;$ (c) a weak acid (CH $_{3} \mathrm{COOH}$ ) reacting with a strong base; (d) a weak acid (CH $_{3}$ COOH) reacting with a weak base $\left(\mathrm{NH}_{3}\right) .$ (Hint: Strong acids exist as $\mathrm{H}^{+}$ ions and strong bases exist as $\mathrm{OH}^{-}$ ions in solution. You need to look up $K_{a}, K_{b},$ and $K_{w^{\prime}}$ )

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 116

Calculate $x,$ which is the number of molecules of water in oxalic acid hydrate, $\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} \cdot x \mathrm{H}_{2} \mathrm{O},$ from
the following data: $5.00 \mathrm{~g}$ of the compound is made up to exactly $250 \mathrm{~mL}$ solution, and $25.0 \mathrm{~mL}$ of this solution requires $15.9 \mathrm{~mL}$ of $0.500 \mathrm{M} \mathrm{NaOH}$ solution for neutralization.

David Collins

Numerade Educator

Problem 117

Describe how you would prepare a 1-L $0.20 \mathrm{M}$ $\mathrm{CH}_{3} \mathrm{COONa} / 0.20 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}$ buffer system
by (a) mixing a solution of $\mathrm{CH}_{3} \mathrm{COOH}$ with a solution of $\mathrm{CH}_{3} \mathrm{COONa},$ (b) reacting a solution of $\mathrm{CH}_{3} \mathrm{COOH}$ with a solution of $\mathrm{NaOH},$ and
(c) reacting a solution of $\mathrm{CH}_{3}$ COONa with a solution of $\mathrm{HCl}$.

Aadit Sharma

Numerade Educator

Problem 118

Phenolphthalein is the common indicator for the titration of a strong acid with a strong base. (a) If the $\mathrm{p} K_{\mathrm{a}}$ of phenolphthalein is $9.10,$ what is the ratio of the nonionized form of the indicator (colorless) to the ionized form (reddish pink) at pH $8.00 ?$ (b) If 2 drops of $0.060 M$ phenolphthalein are used in a titration involving a $50.0-\mathrm{mL}$ volume, what is the concentration of the ionized form at pH $8.00 ?$ (Assume that 1 drop $=0.050 \mathrm{~mL}$.)

Manik Pulyani

Numerade Educator

Problem 119

Oil paintings containing lead(II) compounds as constituents of their pigments darken over the years. Suggest a chemical reason for the color change.

Iryna Ivaniuk

Numerade Educator

Problem 120

What reagents would you employ to separate the following pairs of ions in solution: (a) $\mathrm{Na}^{+}$ and $\mathrm{Ba}^{2+},$ (b) $\mathrm{K}^{+}$ and $\mathrm{Pb}^{2+},$ (c) $\mathrm{Zn}^{2+}$ and $\mathrm{Hg}^{2+} ?$

Prashant Bana

Numerade Educator

Problem 121

Look up the $K_{\mathrm{sp}}$ values for $\mathrm{BaSO}_{4}$ and $\mathrm{SrSO}_{4}$ in Table $16.2 .$ Calculate the concentrations of $\mathrm{Ba}^{2+}$ $\mathrm{Sr}^{2+},$ and $\mathrm{SO}_{4}^{2-}$ in a solution that is saturated with both compounds.

Iryna Ivaniuk

Numerade Educator

Problem 122

In principle, amphoteric oxides, such as $\mathrm{Al}_{2} \mathrm{O}_{3}$ and $\mathrm{BeO},$ can be used to prepare buffer solutions because they possess both acidic and basic properties (see Section 15.11). Explain why these compounds are of little practical use as buffer components.

Prashant Bana

Numerade Educator

Problem 123

$\mathrm{CaSO}_{4}\left(K_{\mathrm{sp}}=2.4 \times 10^{-5}\right)$ has a larger $K_{\mathrm{sp}}$ value than
that of $\mathrm{Ag}_{2} \mathrm{SO}_{4}\left(K_{\mathrm{sp}}=1.4 \times 10^{-5}\right) .$ Does it follow that
$\mathrm{CaSO}_{4}$ also has greater solubility $(\mathrm{g} / \mathrm{L}) ?$

Iryna Ivaniuk

Numerade Educator

Problem 124

When lemon juice is squirted into tea, the color becomes lighter. In part, the color change is due to dilution, but the main reason for the change is an acid-base reaction. What is the reaction? (Hint: Tea contains "polyphenols" which are weak acids and lemon juice contains citric acid.)

Prashant Bana

Numerade Educator

Problem 125

How many milliliters of $1.0 \mathrm{M} \mathrm{NaOH}$ must be added to a $200 \mathrm{~mL}$ of $0.10 \mathrm{M} \mathrm{NaH}_{2} \mathrm{PO}_{4}$ to make a buffer
solution with a pH of $7.50 ?$

Iryna Ivaniuk

Numerade Educator

Problem 126

The maximum allowable concentration of $\mathrm{Pb}^{2+}$ ions in drinking water is $0.05 \mathrm{ppm}$ (that is, $0.05 \mathrm{~g}$ of $\mathrm{Pb}^{2+}$ in 1 million $\mathrm{g}$ of water $) .$ Is this guideline exceeded if an underground water supply is at equilibrium with the mineral anglesite, $\mathrm{PbSO}_{4}\left(K_{\mathrm{sp}}\right.$ $\left.=1.6 \times 10^{-8}\right) ?$

David Collins

Numerade Educator

Problem 127

One of the most common antibiotics is penicillin $\mathrm{G}$ (benzylpenicillinic acid), which has the structure
It is a weak monoprotic acid:
$$
\mathrm{HP} \rightleftharpoons \mathrm{H}^{+}+\mathrm{P}^{-} \quad K_{\mathrm{a}}=1.64 \times 10^{-3}
$$
where HP denotes the parent acid and $\mathrm{P}^{-}$ the conjugate base. Penicillin G is produced by growing molds in fermentation tanks at $25^{\circ} \mathrm{C}$ and a pH range of 4.5 to $5.0 .$ The crude form of this antibiotic is obtained by extracting the fermentation broth with an organic solvent in which the acid is soluble.
(a) Identify the acidic hydrogen atom. (b) In one stage of purification, the organic extract of the crude penicillin G is treated with a buffer solution at $\mathrm{pH}=6.50 .$ What is the ratio of the conjugate base of penicillin G to the acid at this pH? Would you expect the conjugate base to be more soluble in water than the acid? (c) Penicillin G is not suitable for oral administration, but the sodium salt (NaP) is because it is soluble. Calculate the $\mathrm{pH}$ of a $0.12 \mathrm{M}$ NaP solution formed when a tablet containing the salt is dissolved in a glass of water.

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 128

Which of the following solutions has the highest $\left[\mathrm{H}^{+}\right]:$ (a) $0.10 \mathrm{M} \mathrm{HF},$ (b) $0.10 \mathrm{M} \mathrm{HF}$ in $0.10 \mathrm{M} \mathrm{NaF}$
(c) $0.10 \mathrm{M}$ HF in $0.10 \mathrm{M} \mathrm{SbF}_{5} ?$ (Hint: SbF$_{5}$ reacts
with $\mathrm{F}^{-}$ to form the complex ion $\mathrm{SbF}_{6}^{-}$.)

Nicole Smina

Numerade Educator

Problem 129

Distribution curves show how the fractions of nonionized acid and its conjugate base vary as a function of $\mathrm{pH}$ of the medium. Plot distribution curves for $\mathrm{CH}_{3} \mathrm{COOH}$ and its conjugate base $\mathrm{CH}_{3} \mathrm{COO}^{-}$ in solution. Your graph should show fraction as the $y$ axis and $\mathrm{pH}$ as the $\bar{x}$ axis. What are the fractions and $\mathrm{pH}$ at the point where these two curves intersect?

Iryna Ivaniuk

Numerade Educator

Problem 130

Water containing $\mathrm{Ca}^{2+}$ and $\mathrm{Mg}^{2+}$ ions is called hard water and is unsuitable for some household and industrial use because these ions react with soap to form insoluble salts, or curds. One way to remove the $\mathrm{Ca}^{2+}$ ions from hard water is by adding washing soda $\left(\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O}\right) .$ (a) The molar solubility of
$\mathrm{CaCO}_{3}$ is $9.3 \times 10^{-5} \mathrm{M}$. What is its molar solubility in a $0.050 \mathrm{M} \mathrm{Na}_{2} \mathrm{CO}_{3}$ solution? (b) Why are $\mathrm{Mg}^{2+}$
ions not removed by this procedure? (c) The $\mathrm{Mg}^{2+}$ ions are removed as $\mathrm{Mg}(\mathrm{OH})_{2}$ by adding slaked lime $\left[\mathrm{Ca}(\mathrm{OH})_{2}\right]$ to the water to produce a saturated solution. Calculate the $\mathrm{pH}$ of a saturated $\mathrm{Ca}(\mathrm{OH})_{2}$ solution. (d) What is the concentration of $\mathrm{Mg}^{2+}$ ions at this $\mathrm{pH}$ ? (e) In general, which ion $\left(\mathrm{Ca}^{2+}\right.$ or $\mathrm{Mg}^{2+}$ ) would you remove first? Why?

Manik Pulyani

Numerade Educator

Problem 131

Consider the ionization of the following acid-base indicator:
$$
\operatorname{HIn}(a q) \Longrightarrow \mathrm{H}^{+}(a q)+\operatorname{In}^{-}(a q)
$$
The indicator changes color according to the ratios of the concentrations of the acid to its conjugate base as described inSection $16.5 .$ Show that the $\mathrm{pH}$ range over which the indicator changes from the acid color to the base color is $\mathrm{pH}=\mathrm{p} K_{\mathrm{a}} \pm 1,$ where $K_{\mathrm{a}}$ is the ionization constant of the acid.

David Collins

Numerade Educator

Problem 132

Amino acids are building blocks of proteins. These compounds contain at least one amino group $\left(-\mathrm{NH}_{2}\right)$ and one carboxyl group $(-\mathrm{COOH})$ Consider glycine $\left(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{COOH}\right) .$ Depending on the pH of the solution, glycine can exist in one of three possible forms:
$$
\begin{array}{l}
\text { Fully protonated: } \mathrm{NH}_{3}-\mathrm{CH}_{2}-\mathrm{COOH} \\
\text { Dipolar ion: } \mathrm{NH}_{3}-\mathrm{CH}_{2}-\mathrm{COO}^{-} \\
\text {Fully ionized: } \mathrm{NH}_{2}-\mathrm{CH}_{2}-\mathrm{COO}^{-}
\end{array}
$$
Predict the predominant form of glycine at $\mathrm{pH} 1.0$, 7.0, and 12.0. The $\mathrm{p} K_{\mathrm{a}}$ of the carboxyl group is 2.3 and that of the ammonium group $\left(-\mathrm{NH}_{3}^{+}\right)$ is 9.6

Prashant Bana

Numerade Educator

Problem 133

(a) Referring to Figure $16.6,$ describe how you would determine the $\mathrm{p} K_{\mathrm{b}}$ of the base. (b) Derive an analogous Henderson-Hasselbalch equation relating $\mathrm{pOH}$ to $\mathrm{p} K_{\mathrm{b}}$ of a weak base $\mathrm{B}$ and its conjugate acid $\mathrm{HB}^{+} .$ Sketch a titration curve showing the variation of the $\mathrm{pOH}$ of the base solution versus the volume of a strong acid added from a buret. Describe how you would determine the $\mathrm{p} K_{\mathrm{b}}$ from this curve. (Hint:
$\left.\mathrm{pK}_{\mathrm{b}}=-\log K_{\mathrm{b}} .\right)$

David Collins

Numerade Educator

Problem 134

A $25.0-\mathrm{mL}$ of $0.20 \mathrm{M}$ HF solution is titrated with a $0.20 M$ NaOH solution. Calculate the volume of $\mathrm{NaOH}$ solution added when the $\mathrm{pH}$ of the solution is (a) $2.85,$ (b) $3.15,$ (c) $11.89 .$ Ignore salt hydrolysis.

Manik Pulyani

Numerade Educator

Problem 135

Draw distribution curves for an aqueous carbonic acid solution. Your graph should show fraction of species present as the $y$ axis and $\mathrm{pH}$ as the $x$ axis. Note that at any $\mathrm{pH},$ only two of the three species $\left(\mathrm{H}_{2} \mathrm{CO}_{3}, \mathrm{HCO}_{3}^{-},\right.$ and $\left.\mathrm{CO}_{3}^{2-}\right)$ are present
in appreciable concentrations. Use the $\mathrm{p} K_{\mathrm{a}}$ values in Table 15.5

Iryna Ivaniuk

Numerade Educator

Problem 136

One way to distinguish a buffer solution with an acid solution is by dilution. (a) Consider a buffer solution made of $0.500 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}$ and $0.500 M \mathrm{CH}_{3} \mathrm{COONa} .$ Calculate its $\mathrm{pH}$ and the $\mathrm{pH}$ after it has been diluted 10 -fold. (b) Compare the result in (a) with the pHs of a $0.500 \mathrm{M}$ $\mathrm{CH}_{3} \mathrm{COOH}$ solution before and after it has been diluted 10 -fold.

David Collins

Numerade Educator

Problem 137

Histidine is one of the 20 amino acids found in proteins. Shown here is a fully protonated histidine molecule where the numbers denote the $\mathrm{p} K_{\mathrm{a}}$ values of the acidic groups. (a) Show stepwise ionization of histidine in solution. (Hint: The $\mathrm{H}^{+}$ ion will first come off from the strongest acid group followed by the next strongest acid group and so on. $?$ (b) A dipolar ion is one in which the species has an equal number of positive and negative charges. Identify the dipolar ion in
(a). (c) The pH at which the dipolar ion predominates is called the isoelectric point, denoted by pl. The isoelectric point is the average of the $\mathrm{p} \bar{K}_{\mathrm{a}}$ values leading to and following the formation of the dipolar ion. Calculate the $\mathrm{p} I$ of histidine. (d) The histidine group plays an important role in buffering blood (see Chemistry in Action essay "Maintaining the $\mathrm{pH}$ of Blood" in Section 16.4 ). Which conju-

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 138

A sample of $0.96 \mathrm{~L}$ of $\mathrm{HCl}$ at $372 \mathrm{mmHg}$ and $22^{\circ} \mathrm{C}$ is bubbled into $0.034 \mathrm{~L}$ of $0.57 M \mathrm{NH}_{3}$. What is the $\mathrm{pH}$ of the resulting solution? Assume the volume of solution remains constant and that the $\mathrm{HCl}$ is totally dissolved in the solution.

David Collins

Numerade Educator

Problem 139

(a) Assuming complete dissociation and no ionpair formation, calculate the freezing point of a $0.50 \mathrm{~m}$ NaI solution. (b) What is the freezing point after the addition of sufficient $\mathrm{HgI}_{2},$ an insoluble compound, to the solution to react with all the free $\mathrm{I}^{-}$ ions in solution? Assume volume to remain constant.

David Collins

Numerade Educator

Problem 140

Calculate the maximum mass (in grams) of each of the following soluble salts that can be added to $200 \mathrm{~mL}$ of $0.100 \mathrm{M} \mathrm{MgCl}_{2}$ without causing a precipitate to form: (a) $\mathrm{Na}_{2} \mathrm{CO}_{3},$ (b) $\mathrm{AgNO}_{3},$ (c) KOH. Assume volume to remain constant.

David Collins

Numerade Educator

Problem 141

A $1.0-\mathrm{L}$ saturated silver carbonate solution at $5^{\circ} \mathrm{C}$ is treated with enough hydrochloric acid to decompose the compound. The carbon dioxide generated is collected in a $19-\mathrm{mL}$ vial and exerts a pressure of $114 \mathrm{mmHg}$ at $25^{\circ} \mathrm{C}$. What is the $K_{\mathrm{sp}}$ of $\mathrm{Ag}_{2} \mathrm{CO}_{3}$ at $5^{\circ} \mathrm{C} ?$

Iryna Ivaniuk

Numerade Educator

Problem 142

The two curves shown represent the titration of two weak acids of the same concentration with a strong base such as $\mathrm{NaOH}$. Use three observations to determine which of the two acids is stronger.

David Collins

Numerade Educator

Problem 143

The two curves shown represent the titration of two weak bases of the same concentration with a strong acid such as HCl. Use three observations to determine which of the two bases is stronger.

Iryna Ivaniuk

Numerade Educator

Problem 144

A $100-\mathrm{mL} 0.100 \mathrm{M} \mathrm{CuSO}_{4}$ solution is mixed with a $100-\mathrm{mL} 0.100 \mathrm{M} \mathrm{Ba}(\mathrm{OH})_{2}$ solution. Calculate
the concentrations of the ions in the combined solution.

David Collins

Numerade Educator

Problem 145

The titration curve shown represents the titration of a weak diprotic acid $\left(\mathrm{H}_{2} \mathrm{~A}\right)$ versus $\mathrm{NaOH}$. Identify the major species present at the marked points and estimate the $\mathrm{p} K_{\mathrm{a}_{1}}$ and $\mathrm{p} K_{\mathrm{a}_{2}}$ values of the acid.

David Collins

Numerade Educator

Problem 146

The titration curve shown represents the titration of a weak dibasic base (for example, a compound that contains two $-\mathrm{NH}_{2}$ groups) versus HCl. Identify the major species present at the marked points and estimate the $\mathrm{p} K_{\mathrm{a}_{1}}$ and $\mathrm{p} K_{\mathrm{a}_{2}}$ values of the base.

David Collins

Numerade Educator

Problem 147

Use appropriate equations to account for the solubility of the amphoteric aluminum hydroxide $\left.\left[\mathrm{Al}(\mathrm{OH})_{3}\right)\right]$ at low and high $\mathrm{pHs}$

Iryna Ivaniuk

Numerade Educator

Problem 148

From Table 16.2 we see that silver bromide (AgBr) has a larger solubility product than iron(II) hydroxide $\left[\mathrm{Fe}(\mathrm{OH})_{2}\right] .$ Does this mean that $\mathrm{AgBr}$ is more soluble than $\mathrm{Fe}(\mathrm{OH})_{2} ?$

Prashant Bana

Numerade Educator

Problem 149

Aspirin is a weak acid with $\mathrm{p} K_{\mathrm{a}}=3.5 .$ What is the ratio of neutral (protonated) aspirin to deprotonated aspirin in the following body fluids:
(a) saliva,
(b) gastric juices in the stomach, and (c) blood?

Iryna Ivaniuk

Numerade Educator