Unit 4 Acids and Bases Text

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Chapter 8

aCids, Bases, and aCid-Base reaCtions

33

8.1 Strong and Wea

Acids and Bases

8.2 pH and Acidic an

Basic Solutions

8.3 Arrhenius Acid-

Base Reactions

8.4 Brønsted-Lowry

Acids and Bases

Review Skills

Te presentation o inormation in this hapter assumes that you an already perormthe tasks listed below. You an test your readiness to proeed by answering the Review Questions at the end o the hapter. Tis might also be a good time to read the ChapterObjetives, whih preede the Review Questions.

Given a hemial name or ormula,deide whether or not it represents anioni ompound. (Setion 5.3)Desribe what ours when a strong,monoproti aid, suh as HCl, is addedto water. (Setion 6.3)Desribe what ours when a weak,monoproti aid, suh as aeti aid, isadded to water. (Setion 6.3)

Desribe the struture o liquid water.(Setion 7.2)Write a desription o the hanges thattake plae when an ioni ompound isdissolved in water. (Setion 7.2)Predit ioni solubility. (Setion 7.3)Predit the produts o double‑displaement reations. (Setion7.3)

t’s test day in hemistry lass—they’ve been learning about aids and bases—andFran unwisely skips breakast in order to have time or some last‑minute studying. As she reads, she hews on a andy bar and sips a up o oee. Fran is well awarethat the sugary andy stiking to her molars is providing breakast or the bateria

in her mouth, whih in turn produe an aid that will dissolve some o the enamel onher teeth. Feeling a little guilty about all that sugar rom the andy, Fran drinks heroee blak, even though she doesn’t like the taste. Te aeine in her oee is a base,and like all bases, it tastes bitter.

Fran’s junk‑ood breakast and her worrying about the exam ombine to give heran annoying ase o aid indigestion, whih she alms by drinking some baking soda

mixed with water. Te baking soda ontains a base that “neutralizes” some o her exessstomah aid. Ater taking the exam, Fran eels happy and ondent. All those hours working

problems, reviewing the learning objetives, and partiipating in lass really paid o.Now she’s ready or some lunh. Beore eating, she washes her hands with soap maderom the reation o a strong base and animal at.One o the reasons the soap is slippery is beause allbases eel slippery on the skin. o ompensate orher less‑than‑healthy breakast, Fran hooses salad with a piee o lean meat on top or lunh. Like allaids, the vinegar in her salad dressing tastes sour.

Her stomah produes just enough additional aid tostart the digestion o the protein rom the meat.

Read on to learn more about the aids and basesthat are important in Fran’s lie and your own: whatthey are and how they reat with eah other.

The vinegar in salad dressing

tastes sour, as do all acids.



340 Chapter 8 Acids, Bases, and Acid-Base Reactions

8.1 Strong and Weak Acids and Bases

One o the most important goals o this hapater is to broaden your understandingo hemial reations by desribing the hemial hanges that take plae when an aidis ombined with a base. Beore we an do that, we need to review some o what welearned about aids in Chapter 6 and learn about the nature o bases. It might be useulor you to reread Setion 6.3 beore ontinuing with this setion.

Acid Review

In Chapter 6, we learned that aording to the modern orm o the Arrhenius theory,an aid is a substane that produes hydronium ions, H3O+, when it is added to water,and an aidi solution is a solution with a signiant onentration o H3O+. Aids anbe binary aids—suh as HF(aq ), HCl(aq ), HBr(aq ), and HI(aq )—oxyaids, whihhave the general ormula Ha X bO, and organi aids, suh as aeti aid, HC2H3O2.

An aid, suh as hydrofuori aid, HF(aq ), whose moleules an eah donate oneproton, H+, to a water moleule is alled a monoproti aid. Te aids, suh as suluri

aid, H2SO4, that an donate two protons are alled diproti, and some aids, suh as

phosphori aid, H3PO4, are triproti aids.

A strong aid, suh as hydrohlori aid, HCl(aq ), is a substane that undergoes aompletion reation with water suh that eah aid partile reats to orm a hydroniumion, H3O+. Tus strong aids orm nearly one H3O+ ion in solution or eah aidmoleule dissolved in water.

HCl( g )

H2O(l ) Cl

(aq )

H3O

(aq )

Indicates a completion reaction

Suluri aid, H2SO4, is a strong diproti aid. When added to water, eah H2SO4 moleule loses its rst hydrogen ion ompletely.

H2SO4(aq ) + H2O(l ) → H3O+(aq ) + HSO4-(aq )

Te hydrogen sulate ion, HSO4- that orms is a weak aid. It reats with water in a

reversible reation to orm a hydronium ion and a sulate ion.

HSO4-(aq ) + H2O(l ) H3O+(aq ) + SO4

2-(aq )

A weak aid is a substane that is inompletely ionized in water beause o the

reversibility o its reation with water that orms hydronium ion, H3O+. Weak aidsyield signiantly less than one H3O+ ion in solution or eah aid moleule dissolvedin water.

HC2H3O2(aq ) H2O(l ) C2H3O2(aq H3O(aq )

Indicates a

reversible

reaction

Te strong aids that you will be expeted to reognize are hydrohlori aid,HCl(aq ), nitri aid, HNO3, and suluri aid, H2SO4. (Tere are other strong aids,but they are muh less ommon.) An aid is onsidered weak i it is not on the list o strong aids.

oBjeCtive 5



8.1 Strong and Weak Acids and Bases 34

Bases

Eah year, the US hemial industry produes over 10 billion kilograms o the basesodium hydroxide, NaOH, whih is then used or many purposes, inluding watertreatment, vegetable oil rening, the peeling o ruits and vegetables in the ood industry,and to make numerous other hemial produts, inluding soaps and detergents.

Likewise, over 15 billion kilograms o the base ammonia, NH3,is produed eah year. Although a water solution o ammonia isa ommon household leaner, most o the NH3 produed in theUS is used to make ertilizers and explosives. As you read thissetion, you will learn about the hemial properties o basiompounds that make them so useul to hemists and others.

Aording to the modern version o the Arrhenius theory o

aids and bases, a base is a substane that produes hydroxideions, OH-, when it is added to water. A solution that has a

signiant onentration o hydroxide ions is alled a basic

solution. Sodium hydroxide, NaOH, is the most ommonlaboratory base. It is designated a strong base beause orevery NaOH unit dissolved, one hydroxide ion is ormed insolution.

NaOH(aq ) → Na+(aq ) + OH-(aq )

Compounds that ontain hydroxide ions are oten alled hydroxides. All water‑soluble hydroxides are strong bases. Examples inlude lithium hydroxide, LiOH, whih is used in storage batteries and as a arbon dioxide absorbent in spae vehiles,and potassium hydroxide, KOH, whih is used to make some soaps, liquid ertilizers,and paint removers.

When ammonia, NH3, dissolves in water, some hydrogen ions, H+, are transerredrom water moleules to ammonia moleules, NH3, produing ammonium ions,NH4

+, and hydroxide ions, OH-. Te reation is reversible, so when an ammoniumion and a hydroxide ion meet in solution, the H+ ion an be passed bak to the OH- toreorm an NH3 moleule and a water moleule (Figure 8.1).

NH3(aq ) H2O(l ) NH4(aq ) OH(aq )

Indicates areversiblereaction

+

is proton, H, istransferred to anammonia molecule.

is proton, H, may be transferred back to the hydroxide ion.

Figure 8.1The Reversible Reaction

of Ammonia and Water

oBjeCtive 3

oBjeCtive 3

oBjeCtive 2

This water treatment plant uses the

base sodium hydroxide, NaOH, toremove impurities from the water.




Ammonia is an Arrhenius base beause it produes OH- ions when added to

water. Beause the reation is reversible, however, only some ammonia moleules have

aquired protons (reating OH-) at any given time, so an ammonia solution ontains

ewer hydroxide ions than would be ound in a solution made using an equivalent

amount o a strong base. Tereore, we lassiy ammonia as a weak base, whih is a

base that produes ewer hydroxide ions in water solution than there are partiles o base dissolved.

o visualize the reation between ammonia and water at the moleular level, imagine

that you are taking a ride on a nitrogen atom. Your nitrogen would usually be bonded

with three hydrogen atoms in an NH3 moleule, but oasionally, it would gain an

extra H+ ion rom a water moleule to orm NH4+ or a short time. When your NH4

+

ion ollides with an OH- ion, an H+ ion is transerred to the OH- ion to orm H2O

and NH3. Ammonia moleules are onstantly gaining and losing H+ ions, but soon

ater the initial addition o ammonia to water, both hanges proeed at an equal rate.

At this point, there will be no more net hange in the amounts o ammonia, water,

hydroxide, and ammonium ion in the solution. When a typial solution o ammonia

stops hanging, it is likely to ontain about 200 NH3 moleules or eah NH4+ ion. As

you study the ammonia solution depited in Figure 8.2, try to piture about 200 times

as many NH3 moleules as NH4+ or OH- ions.

Figure 8.2Ammonia in Water

+

−

100

400

300

200

500

Hydroxide ion, OH−,surrounded by the

positively chargedhydrogen ends of

water molecules

Ammonium ion, NH4+,

surrounded by thenegatively chargedoxygen ends of

water molecules.

In a typical ammonia solution, there are about 200 times as many uncharged ammonia molecules, NH3, as ammonium ions NH4

+.

oBjeCtive 3

oBjeCtive 3




Tere are many weak Arrhenius bases, but the only ones that you will be expeted to

reognize are ioni ompounds ontaining arbonate (or example, sodium arbonate,

Na2CO3) and hydrogen arbonate (or example, sodium hydrogen arbonate,

NaHCO3). When sodium arbonate, whih is used to make glass, soaps, and detergents,

dissolves in water, the arbonate ions, CO32-, reat with water in a reversible way to

yield hydroxide ions.

Na2CO3(s ) → 2Na+(aq ) + CO32-(aq )

CO32-(aq ) + H2O(l ) HCO3

-(aq ) + OH-(aq )

In a similar reation, the hydrogen arbonate ions, HCO3-, ormed when NaHCO3

dissolves in water, reat to yield hydroxide ions.

NaHCO3(s ) → Na+(aq ) + HCO3-(aq )

HCO3-(aq ) + H2O(l ) H2CO3(aq ) + OH-(aq )

Sodium hydrogen arbonate is ound in re extinguishers, baking powders, antaids,and mouthwashes.

Table 8.1

Arrhenius Bases

Srong Wak

Ioni ompounds Metal hydroxides,suh as NaOH

Ioni ompounds with CO32- and

HCO3-, suh as Na2CO3 and

NaHCO3

Certain unhargedmoleules

None NH3

These products all

contain the weak base

sodium hydrogen

carbonate.

able 8.1 summarizes how you an reognize substanes as bases and how you an

lassiy them as strong or weak bases. (Tere are other Arrhenius bases that you may

learn about later.)

oBjeCtive 4

oBjeCtive 5

You can g mor

inormaion

abou srong and

wak bass on

h xbook’s

Wb si.

oBjeCtive 4

http://www.preparatorychemistry.com/Bishop_Base_Identification.htm















example 8.1 - Identication of Acids and Bases

Identiy (a) H2SO4, (b) oxali aid, () NaHCO3, (d) potassium hydroxide, (e)

HCl(aq ), and ( ) ammonia as either an Arrhenius strong aid, an Arrhenius weak

aid, an Arrhenius strong base, or an Arrhenius weak base.

Solution

a. Te H2SO4 is an aid beause it has the orm o an oxyaid, Ha X bO. It is

on the list o srong acids.

b. Oxali aid is not on the list o strong aids—HCl(aq ), HNO3, and

H2SO4—so it is a wak acid.

. Ioni ompounds that ontain hydrogen arbonate, suh as NaHCO3, are

wak bass.

d. Ioni ompounds that ontain hydroxide, suh as potassium hydroxide, are

srong bass.

e. We know that hydrohlori aid, HCl(aq ), is an aid beause its name ends

in “aid,” and its ormula has the orm o a binary aid. It is ound on the

list o srong acids.

. Ammonia, NH3, is our one example o an unharged wak bas.

oBjeCtive 5

Te ollowing sample study sheet summarizes the ways you an reognize strong and

weak aids and bases.

Tip-off You are asked to identiy a substane as either (1) an Arrhenius strong aid, (2)

an Arrhenius weak aid, (3) an Arrhenius strong base, or (4) an Arrhenius weak base.

General STepS

Step 1 Identiy the substane as an Arrhenius aid or base using the ollowing

riteria.

Te names o the aids end in acid . Aid ormulas have one o these

orms: HX(aq ) or Ha X bO.

Ioni ompounds that ontain hydroxide, arbonate, or hydrogen

arbonate anions are basi. Ammonia, NH3, is also a base. Step 2 I the substane is an aid or base, determine whether it is strong or

weak.

We will onsider all aids exept HCl(aq ), HNO3, and H2SO4 to be

weak.

We will onsider all bases exept metal hydroxides to be weak.

e xample See Example 8.1.

oBjeCtive 5

Sample Study

Sheet 8.1

Identication

of Strong and

Weak Acids

and Bases

Tr is a uorial onh xbook’s

Wb si ha will rovid

racicidniyingacids and bass.

http://www.preparatorychemistry.com/Bishop_acid_base_frames.htm



















SPECIAL TOPIC 8.1 Chemistry and Your Sense of Taste

“…[T]hat formed of bodies round and smooth are things which touch the senses sweetly, while those

which harsh and bitter do appear,are held together bound with particles more hooked, and for this cause are wont to tear their way into our senses, and on entering in to rend the body.”

Luretius, a Roman philosopher andpoet, about 2000 years ago

Luretius was mistaken in ertain details, but he

was orret that the shape o moleules is important in

determining whether ompounds taste sweet or bitter.

Your tongue has about 3000 taste buds, eah o whih is

an onion‑shaped olletion o 50 to 150 taste ells. Eahtaste bud is speialized or tasting either sweet, sour, salt,

or bitter. It has been suggested that the tongue an also

pereive another taste, umami, whih is a subtle taste most

ommonly assoiated with monosodium glutamate, MSG.

At the tips o the bitter and sweet taste ells are reeptor

moleules shaped to t parts o ertain moleules in our

ood.

When hoolate, or example, is roasted, aeine and

other ompounds are ormed that stimulate the bitter taste

ells. Te moleules o these ompounds have a shape that

allows them to attah to the taste ell reeptors and ause an

adjaent nerve ell to re. Tis event sends the bitter signalto the brain.

Sugar is added to hoolate to ounterat the bitter taste.

Te arrangement o atoms in sugar moleules allows them to

t into the reeptor sites o sweet taste ells. When a sugar

moleule suh as gluose or surose attahes to a reeptor o

a sweet taste ell, the sweet signal is sent to the brain.

Te salt taste is thought to have dierent mehanisms

than the sweet and bitter tastes. It is the presene o sodium

ions, Na+, in the sodium hloride, NaCl, o table salt that

auses the taste. Te interior o a salt taste ell is negatively

harged. When suh

a ell is bathed in

saliva that ontains

dissolved sodiumions, the Na+ ions

enter the ell and

make its interior less

negative. Tis hange

triggers the release

o hemials alled

neurotransmitters

into the spae

between the taste ells

and nerve ells. Te

neurotransmitters ause

the nerve ells to re, sending the salt signal to the brain. Aids ause the sour taste in oods. Vinegar is sour

beause it ontains aeti aid, sour milk ontains lati

aid, and lemons ontain itri aid. What these aids have

in ommon is that they an lose H+ ions in water solutions

suh as our saliva. Dierent animal speies have dierent

mehanisms or sending the sour signal. In amphibians

the H+ ions blok the normal release o potassium ions

rom sour taste ells, hanging the ells’ harge balane

and ausing them to release neurotransmitters. Te

neurotransmitters in turn tell the sour nerve ells to re.

It has been suggested that there are good reasons or the

evolution o our sense o taste. Te our main tastes eitherlead us to ood we need or warn us away rom substanes

that might be harmul. We need sugar or energy and salt

to replae the sodium and potassium ions lost in exerise.

On the other hand, spoiled oods produe bitter‑tasting

substanes, and numerous poisons, too, are bitter, while

many a bellyahe rom unripe ruit has been avoided by the

warning signal provided by the sour taste.

exerCise 8.1 - Identication of Acids and Bases

Identiy eah o the ollowing as either an Arrhenius strong aid, an Arrhenius weak aid, an Arrhenius strong base, or an Arrhenius weak base.

a. HNO3

b. lithium hydroxide

. K 2CO3

d. hydrofuori aid

oBjeCtive 5

Bases taste bitter.




8.2 pH and Acidic and Basic Solutions

Te sienti term pH has rept into our everyday language. Advertisements enourage

us to hoose produts that are “pH balaned,” while environmentalists point to the

lower pH o rain in ertain parts o the ountry as a ause o eologial damage (Figure

8.3). Te term was originated by hemists to desribe the aidi and basi strengths o

solutions.

Figure 8.3Acid Rain

The map on the left shows the

pH of rain in different parts of

the U.S. in 1992. The scale

on the left shows the effect on

sh of decreasing pH.

pH-Balanced Shampoo

We know that an Arrhenius aid donates H+ ions to water to reate H3O+ ions.Te resulting solution is alled an aidi solution. We also know that when you adda ertain amount o a strong aid to one sample o water—say the water’s volume isa liter—and add the same amount o a weak aid to another sample o water whose

volume is also a liter, the strong aid generates more H3O+

ions in solution. Beausethe onentration o H3O+ ions in the strong aid solution is higher (there are moreH3O+ ions per liter o solution), we say it is more aidi than the weak aid solution. A solution an also be made more aidi by the addition o more aid (while the amounto water remains the same). Te pH sale an be used to desribe the relative aidity o solutions.

I you take other hemistry ourses, you will probably learn how pH is dened andhow the pH values o solutions are determined. For now, all you need to remember isthat aidi solutions have pH values less than 7, and that the more aidi a solutionis, the lower its pH. A hange o one pH unit refets a ten‑old hange in H3O+ iononentration. For example, a solution with a pH o 5 has ten times the onentration

oBjeCtive 6

oBjeCtive 7

4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5



8.2 pH and Acidic and Basic Solutions 34

o H3O+ ions as a solution with a pH o 6. Te pH o some ommon solutions are

listed in Figure 8.4. Note that gastri juie in our stomah has a pH o about 1.4, and

orange juie has a pH o about 2.8. Tus gastri juie is more than ten times more

onentrated in H3O+ ions than orange juie.

Te pH sale is also used to desribe basi solutions, whih are ormed when an

Arrhenius base is added to water, generating OH- ions. When you add a ertain

amount o a strong base to one sample o water—again, let’s say a liter—and add the

same amount o a weak base to another sample o water whose volume is the same,

the strong base generates more OH- ions in solution. Beause the onentration o

OH- ions in the strong base solution is higher (there are more OH- ions per liter

o solution), we say it is more basi than the weak base solution. A solution an also

be made more basi by the addition o more base while the amount o water is held

onstant.

Basi solutions have pH values greater than 7, and the more basi the solution is,

the higher its pH. A hange o one pH unit refets a ten‑old hange in OH-

iononentration. For example, a solution with a pH o 12 has ten times the onentration

o OH- ions as does a solution with a pH o 11. Te pH dierene o about 4 between

household ammonia solutions (pH about 11.9) and seawater (pH about 7.9) shows

that household ammonia has about ten thousand (104) times the hydroxide ion

onentration o seawater.

In nature, water ontains dissolved substanes that make it slightly aidi, but pure

water is neutral and has a pH o 7 (Figure 8.4).

pH

g a s t r i c

j u i c e

o r a n g

e j u i c e

c o ff

e e

b

l o o d

w i n e

m

i l k p u r e

w a t e r

h

o u s e h

o l d a m

m o n i a

d e t e r g e

n t s

b l e a c h

s e a w

a t e r

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

More Acidic More BasicNeutral

Acidic solutions have pHvalues less than 7.

Basic solutions have pHvalues greater than 7.

Figure 8.4pH of Common Substances

oBjeCtive 6

oBjeCtive 8

oBjeCtive 6 oBjeCtive 7 oBjeCtive 8




When an Arrhenius aid is ombined with an Arrhenius base,

we say that they neutralize eah other. By this, we mean thatthe aid ounterats the properties o the base, and the baseounterats the properties o the aid. For example, a strongaid, suh as nitri aid, must be handled with extremeaution, beause i it gets on your skin, it ould ause severehemial burns. I you aidentally spilled nitri aid on alaboratory benh, however, you ould quikly pour a solutiono a weak base, suh as sodium hydrogen arbonate, on topo the spill to neutralize the aid and make it saer to wipe. Ina similar way, a solution o a weak aid, suh as aeti aid,

an be poured on a strong base spill to neutralize the basebeore leanup. Tereore, reations between Arrhenius aidsand bases are oten alled neutralization reactions.

Neutralization reations are important in maintainingthe neessary balane o hemials in your body, andthey help keep a similar balane in our oeans and lakes.Neutralization reations are used in industry to make a widerange o produts, inluding pharmaeutials, ood additives,and ertilizers. Let’s look at some o the dierent orms o Arrhenius aid‑base reations, how they an be visualized,and how to desribe them with hemial equations.

8.3 Arrhenius Acid-Base Reactions

Neutralization reactions keep our bodies in

balance and also maintain the “health” of the

world around us.

In the laboratory, we an detet aids and bases in solution in several ways. Perhaps

the simplest test uses a substane alled litmus, a natural dye derived rom lihen. It

turns red in aidi onditions and blue in

basi onditions. Litmus paper is paper that

has been oated with litmus. o test i a liquid

is aidi, we add a drop o the liquid to blue

litmus paper, whih is litmus paper that has

been made slightly basi and thereore blue.

I the paper turns red, the liquid is aidi.

o test to see i a liquid is basi, we add a

drop o the liquid to red litmus paper, whih

is litmus paper that has been made slightly

aidi and thereore red. I the paper turns

blue, the liquid is basi.

Litmus, whose natural source is lichen, can

be applied to the surface of paper that is then

used to identify acidic and basic solutions.

oBjeCtive 9



8.3 Arrhenius Acid-Base Reactions 34

Reactions of Aqueous Strong Arrhenius Acids and Aqueous Strong

Arrhenius Bases

Te reation between the strong aid nitri aid and the strong base sodium hydroxide

is our rst example. Figure 8.5 shows the behavior o nitri aid in solution. As a

strong aid, virtually every HNO3 moleule donates an H+ ion to water to orm a

hydronium ion, H3O+, and a nitrate ion, NO3-. Beause the reation goes essentially

to ompletion, you an piture the solution as ontaining H2O, NO3-, and H3O+,

with no HNO3 remaining. Te negatively harged oxygen ends o the water moleules

surround the positive hydronium ions, and the positively harged hydrogen ends o

water moleules surround the nitrate ions.

+

+

+

+

+

+

-

- -

-

-

-

+

+

+

+

+

-

−

-−

−

-

+

+

+ +

+

+−

−

−

−

−

−

100

400

300

200

500

Hydronium ions, H3O+,surrounded by thenegatively chargedoxygen ends of water molecules.

Nitrate ions, NO3−,

surrounded by thepositively charged

hydrogen ends of water molecules.

Figure 8.5

Aqueous Nitric Acid

Like a water solution o any ioni ompound, a solution o sodium hydroxide

(NaOH) onsists o ions separated and surrounded by water moleules. At the instant

that the solution o sodium hydroxide is added to the aqueous nitri aid, there are

our dierent ions in solution surrounded by water moleules: H3O+, NO3-, Na+, and

OH- (Figure 8.6 on the next page).

oBjeCtive 10a

oBjeCtive 10a






-

-

-

-

-

-

+

+

+

+

+

+

-

-

-

-

-

+

+

+

+

+

+

−

+

−

−

−

−

−

+

+

+

+

+

100

400

300

200

500

Nitrate ion, NO3−

Sodium ion, Na+

After the reaction between nitric acidand sodium hydroxide,hydroxide ions, OH−, andhydronium ions, H3O+,have combined to

form water, H2O.

e sodium ions, Na+, andnitrate ions, NO3

−,remain in solution

in the same formthey were in

before thereaction.

Figure 8.8After Reaction of Nitric Acid and Sodium Hydroxide

Te sodium and nitrate ions are unhanged in the reation. Tey were separate andsurrounded by water moleules at the beginning o the reation, and they are stillseparate and surrounded by water moleules ater the reation. Tey were importantin delivering the hydroxide and hydronium ions to solution, but they did not atively partiipate in the reation. In other words, they are spetator ions, so they are let

out o the net ioni hemial equation. Te net ioni equation or the reation isthereore

H3O+(aq ) + OH-(aq ) → 2H2O(l )

Most hemists are in the habit o desribing reations suh as this one in terms o H+ rather than H3O+, even though hydrogen ions do not exist in a water solution in thesame sense that sodium ions do. When an aid loses a hydrogen atom as H+, the protonimmediately orms a ovalent bond to some other atom. In water, it orms a ovalentbond to a water moleule to produe the hydronium ion. Although H3O+ is a betterdesription o what is ound in aid solutions, it is still onvenient and onventional to write H+ in equations instead. You an think o H+ as a shorthand notation or H3O+.

Tereore, the ollowing net ioni equation is a ommon way to desribe the net ioniequation above.

H+(aq ) + OH-(aq ) → H2O(l )

oBjeCtive 10a

oBjeCtive 10a

Writing Equations for Reactions Between Acids and Bases

Te proedure or writing equations or aid‑base reations is very similar to that usedto write equations or preipitation reations in Setion 7.3.

Te rst step in writing an equation or the reation between nitri aid, HNO3,and the base sodium hydroxide, NaOH, is to predit the ormulas or the produtsby reognizing that most Arrhenius neutralization reations, like the reation between

oBjeCtive 11






b. For H2SO4 in a double‑displaement reation, A is H+, and B is SO42-.

(In neutralization reations, you an assume that all o the aidi hydrogen

atoms are lost to the base. Monoproti aids lose one H+ ion, diproti aids

suh as H2SO4 lose two H+ ions, and triproti aids suh as H3PO4 lose

three H+ ions.) For KOH, C is K +, and D is OH-. Tus AD is H2O, and

CB is K 2SO4, a water‑soluble ioni ompound. Te two H+ ions rom the

diproti aid H2SO4 reat with the two OH- ions rom two units o KOH

to orm two H2O moleules.

AB + CD → AD + CB

HSO4(aq ) + KOH(aq ) → HO(l ) + K SO4(aq )

. For HNO3

in a double‑displaement reation, A is H+, and B is NO3-.

For Mn(OH)2, C is Mn2+, and D is OH-. Tus AD is H2O, and CB is

Mn(NO3)2, a water‑soluble ioni ompound. wo H+ ions rom two nitri

aid moleules reat with the two OH- ions rom the Mn(OH)2 to orm

two H2O moleules.

AB + CD → AD + CB

HNO3(aq ) + Mn(OH)(s ) → HO(l ) + Mn(NO3)(aq )

exerCise 8.2 - Neutralization Reactions

Write the omplete equation or the neutralization reations that take plae when theollowing water solutions are mixed. (I an aid has more than one aidi hydrogen,assume that there is enough base to remove all o them. Assume that there is enough

aid to neutralize all o the basi hydroxide ions.)a. HCl(aq ) + NaOH(aq )b. HF(aq ) + LiOH(aq ). H3PO4(aq ) + LiOH(aq )d. Fe(OH)3(s ) + HNO3(aq )

oBjeCtive 11

Reactions of Arrhenius Acids and Ionic Compounds Containing Carbonate or Hydrogen Carbonate

Te reation between an aid and an ioni ompound ontaining either arbonate or

hydrogen arbonate leads to arbon dioxide and water as produts. Te addition o

H+ ions to CO32- or HCO3

- orms arboni aid, H2CO3. Carboni aid, however,

is unstable in water, so when it orms, it deomposes into arbon dioxide, CO2( g ),and water, H2O(l ).

2H+(aq ) + CO32-(aq ) → H2CO3(aq ) → H2O(l ) + CO2( g )

H+(aq ) + HCO3-(aq ) → H2CO3(aq ) → H2O(l ) + CO2( g )

oBjeCtive 12

oBjeCtive 10C

Tr is an animaion ha will hl you visualiz racions bwn acids and

bass a h xbook’s Wb si.

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The natural enamel that coats teeth is mostly

Ca5(PO4)3OH. Fluoride in our water or toothpaste

leads to the less soluble Ca5(PO4)3F replacing

Ca5(PO4)3OH in tooth enamel, helping to protect our

teeth from tooth decay.

SPECIAL TOPIC 8.2 Precipitation, Acid-Base Reactions,

and Tooth Decayeeth have a protetive oating o hard enamel that is about

2 mm thik and onsists o about 98% hydroxyapatite,

Ca5(PO4)3OH. Like any ioni solid surrounded by a water

solution, the hydroxyapatite is onstantly dissolving and

repreipitating.

Ca5(PO4)3OH(s )

5Ca2+(aq ) + 3PO43-(aq ) + OH-(aq )

Your saliva provides the alium ions and the phosphate

ions or this proess, and as long as your saliva does not get

too aidi, it will ontain enough hydroxide to keep the rate

o solution and the rate o preipitation about equal. Tus

there is no net hange in the amount o enamel on your

teeth.

Unortunately, ertain oods an upset this balane.

Te bateria in your mouth break down your ood,

espeially ood high in sugar, to orm aids suh as aeti

aid and lati aid. Tese aids neutralize the hydroxide

in your saliva, slowing the preipitation o enamel. Te

Ca5(PO4)3OH ontinues to go into solution, so there is a

net loss o the protetive oating on the teeth.

Fluoride in our drinking water and our toothpaste an

help minimize the damage desribed above. Te fuoride

ion takes the plae o the hydroxide ion to preipitate

fuorapatite, Ca5(PO

4)3F, a ompound very similar to the

original enamel.

5Ca2+(aq ) + 3PO43-(aq ) + F-(aq )

Ca5(PO4)3F(s )

Fluorapatite is 100 times less soluble than hydroxyapatite,

so it is less likely to be aeted by the aid ormed by the

bateria.

Tus, when H2CO3 would be predited as a produt or a double‑displaement

reation, write “H2O(l ) + CO2( g )” instead. Tree examples are below.

2HCl(aq ) + Na2CO3(aq ) → H2O(l ) + CO2( g ) + 2NaCl(aq )

HCl(aq ) + NaHCO3(aq ) → H2O(l ) + CO2( g ) + NaCl(aq )

2HCl(aq ) + CaCO3(s ) → H2O(l ) + CO2( g ) + CaCl2(aq )

Te third equation above desribes a reation that helps the oil industry extrat more

oil rom a well. For oil to be pumped rom deep in the earth to the surae, it must

rst seep through underground rok ormations to the base o the oil well’s pipes.

Limestone, whih is omposed o CaCO3, an be made more permeable to oil by

pumping hydrohlori aid down into the limestone ormations, onverting the

insoluble alium arbonate to soluble alium hloride.

oBjeCtive 11

Acids can be used

to make limestone

more permeable to

oil by converting solid

calcium carbonate into

water-soluble calcium

chloride.






Do you want to know why bleah bottles have a warning label that tells you not tomix the bleah with aidi leaning agents, suh as toilet bowl leaners? Te explanationis in Speial opi 8.4 below.

8.4 Brønsted-Lowry Acids and Bases

Although the Arrhenius denitions o aid, base, and aid‑base reation are very useul, an alternate set o denitions is also ommonly employed. In this system, aBrønsted‑Lowry acid is a proton (H+) donor, a Brønsted‑Lowry base is a protonaeptor, and a Brønsted‑Lowry acid‑base reaction is a proton transer. able 8.2summarizes the denitions o aid and base in the Arrhenius and Brønsted‑Lowry

systems.

Table 8.2

Denitions of Acid and Base

Sysm Acid Dfniion Bas Dfniion

Arrhenius Generates H 3O+ when addedto water

Generates OH- when addedto water

Brønsted‑Lowry Proton (H+) Donor inReation

Proton (H+) Aeptor inReation

Common bleah, used or household leaning and

laundering, is a water solution o sodium hypohlorite,

NaClO(aq ). Te hypohlorite ion is made by reating

hlorine gas with a basi solution.

Cl2( g ) + 2OH-(aq )

OCl-(aq ) + Cl-(aq ) + H2O(l )

Tis reation is reversible, so the hlorine atoms are

onstantly swithing bak and orth rom Cl2 to OCl-

. In abasi solution, the orward reation is ast enough to ensure

that most o the hlorine in the bottle o bleah is in the

OCl- orm.

I the bleah is added to an aidi solution, the hydroxide

ions in the basi solution o bleah reat with the aidi H+

ions to orm water. With ewer hydroxide ions available,

the reation between the OH- and the Cl2 slows down, but

the reverse reation ontinues at the same pae. Tis reates

potentially dangerous levels o hlorine gas and is the reason

that the labels on bleah bottles warn against mixing bleah

with other leaning agents suh as toilet bowl leaners.

oilet bowl leaners are usually aidi, ontaining aids suh

as phosphori aid, H3PO4, or hydrogen sulate, HSO4-.

SPECIAL TOPIC 8.4 Be Careful with Bleach

Mixing bleach

and toilet bowl

cleaners can be

dangerous.



8.4 Brønsted-Lowry Acids and Bases 35

o better understand the dierenes and to understand why new denitions were

suggested, onsider the ollowing reations.

NH3(aq ) + HC2H3O2(aq ) → NH4+(aq ) + C2H3O2

-(aq )

H2O(l ) + HC2H3O2(aq ) H3O+(aq ) + C2H3O2-(aq )

NH3(aq ) + H2O(l ) NH4+(aq ) + OH-(aq )

Tese reations are very similar, but only the rst reation would be onsidered an

aid‑base reation in the Arrhenius system. In eah o the reations, an H+ is transerred

rom one reatant to another, but only the rst is a reation between an Arrhenius aid

and an Arrhenius base. In the rst reation, an H+ is transerred rom the Arrhenius

weak aid aeti aid, HC2H3O2(aq ), to the Arrhenius weak base ammonia, NH3(aq ).

In the seond reation, an H+ is transerred rom the Arrhenius weak aid aeti aid,

HC2H3O2(aq ), to water, whih is not onsidered an aid or a base in the Arrhenius

sense. In the third reation, an H+ is transerred rom water, whih is not onsidered anaid or base in the Arrhenius sense, to the Arrhenius weak base ammonia, NH3(aq ).

Te Brønsted‑Lowry system allows us to desribe all o these reations as aid‑base

reations. Tey are repeated below, with the Brønsted‑Lowry aids and bases labeled.

Note that in eah ase, the aid loses an H+ ion as it reats, and the base gains an H+

ion.

NH3(aq ) + HC2H3O2(aq ) → NH4+(aq ) + C2H3O2

-(aq )B/L base B/L aid

H2O(l ) + HC2H3O2(aq ) H3O+(aq ) + C2H3O2-(aq )

B/L base B/L aid

NH3(aq ) + H2O(l ) NH4+(aq ) + OH-(aq )

B/L base B/L aid

Aeti aid reats with the dihydrogen phosphate polyatomi ion, H2PO4-, in a

reversible reation. In the orward reation, aeti aid ats as the Brønsted‑Lowry aid

and dihydrogen phosphate ats as the Brønsted‑Lowry base

HC2H3O2(aq ) + H2PO4-(aq ) C2H3O2

-(aq ) + H3PO4(aq )

B/L aid B/L base

Te reverse reation, too, is a Brønsted‑Lowry aid‑base reation. An H+ ion is

transerred rom H3PO4 (the aid) to a C2H3O2- ion (the base). Te Brønsted‑Lowry

base or the orward reation (H2PO4-) gains an H+ ion to orm H3PO4, whih

then ats as a Bronsted‑Lowry aid in the reverse reation and returns the H + ion to

C2H3O2-. Chemists say that H3PO4 is the onjugate aid o H2PO4

-. Te conjugate

acid o a moleule or ion is the moleule or ion that orms when one H+ ion is added.

Te ormulas H3PO4 and H2PO4- represent a conjugate acid‑base pair, moleules or

ions that dier by one H+ ion.

oBjeCtive 13

oBjeCtive 14

oBjeCtive 13




Likewise, the Brønsted‑Lowry aid or the orward reation (HC2H3O2) loses an H+ ion to orm C2H3O2

-, whih ats as a Bronsted‑Lowry base in the reverse reation andregains the H+ ion. Chemists say that C2H3O2

- is the onjugate base o HC2H3O2.Te conjugate base o a moleule or ion is the moleule or ion that orms whenone H+ ion is removed. Te ormulas HC2H3O2 and C2H3O2

- represent a onjugate

aid‑base pair (Figure 8.9).

oBjeCtive 15

Figure 8.9Congugate Acid-Base

Pairs

Proton Proton Proton Protondonor acceptor acceptor donor

Conjugateacid-base pair

Conjugateacid-base pair

H+H+

+ +

example 8.4 - Conjugate Acids

Write the ormula or the onjugate aid o (a) F-, (b) NH3, () HSO4-, and

(d) CrO42-.

Solution

In eah ase, the ormula or the onjugate aid is derived by adding one H+ ion to

the ormulas above.

a. HF b. NH4+ . HSO4 d. HCrO4

-

oBjeCtive 14

exerCise 8.4 - Conjugate Acids

Write the ormula or the onjugate aid o (a) NO2-, (b) HCO3

-, () H2O, and(d) PO4

3-.

oBjeCtive 14

example 8.5 - Conjugate Bases

Write the ormula or the onjugate base o (a) HClO3, (b) H2SO3, () H2O, and

(d) HCO3-.

Solution

In eah ase, the ormula or the onjugate base is derived by removing one H+ ion

rom the ormulas above.

a. ClO3- b. HSO3

- . OH- d. CO3-

oBjeCtive 15

exerCise 8.5 - Conjugate Bases

Write the ormula or the onjugate base o (a) H2C2O4, (b) HBrO4, () NH3, and(d) H2PO4

-.

oBjeCtive 15



8.4 Brønsted-Lowry Acids and Bases 35

Some substanes an at as a Brønsted‑Lowry aid in one reation and a

Brønsted‑Lowry base in another. Consider the ollowing net ioni equations or the

reation o dihydrogen phosphate ion with either the aid hydrohlori aid or the

strong base hydroxide.

H2PO4-(aq ) + HCl(aq ) → H3PO4(aq ) + Cl-(aq )

B/L base B/L aid

H2PO4-(aq ) + 2OH-(aq ) → PO4

3-(aq ) + 2H2O(l )B/L aid B/L base

In the rst reation, the dihydrogen phosphate ats as a Brønsted‑Lowry base, and in

the seond reation, it ats as a Brønsted‑Lowry aid. A substane that an at as either

a Brønsted‑Lowry aid or a Brønsted‑Lowry base, depending on the irumstanes, is

alled an amphoteric substane.Te hydrogen arbonate ion is another example o an amphoteri substane. In the

rst reation below, it ats as a Brønsted‑Lowry base, and in the seond reation, it ats

as a Brønsted‑Lowry aid.

HCO3-(aq ) + HC2H3O2(aq ) → H2O(l ) + CO2( g ) + C2H3O2

-(aq )B/L base B/L aid

HCO3-(aq ) + OH-(aq ) → CO3

2-(aq ) + H2O(l )B/L aid B/L base

Beause both dihydrogen phosphate and hydrogen arbonate (and other substanes

like them) an be either Brønsted‑Lowry aids or bases, they annot be desribed as a

Brønsted‑Lowry aid or base exept with reerene to a spei aid‑base reation. For

this reason, the Arrhenius denitions o aids and bases are the ones used to ategorize

isolated substanes on the stokroom shel. A substane generates either hydronium

ions, hydroxide ions, or neither when added to water, so it is always either an aid,

a base, or neutral in the Arrhenius sense. Hydrogen arbonate is an Arrhenius base

beause it yields hydroxide ions when added to water. Dihydrogen phosphate is an

Arrhenius aid beause it generates hydronium ions when added to water.

HCO3-(aq ) + H2O(l ) H2CO3(aq ) + OH-(aq )

H2PO4-(aq ) + H2O(l ) HPO4

2-(aq ) + H3O+(aq )

Tus we have two systems or desribing aids, bases, and aid‑base reations. Te

Brønsted‑Lowry system is oten used to desribe spei aid‑base reations, but the

Arrhenius system is used to desribe whether isolated substanes are aids, bases, or

neither.

oBjeCtive 17

oBjeCtive 16




example 8.6 - Brønsted-Lowry Acids and Bases

Identiy the Brønsted‑Lowry aid and base or the orward reation in eah o theollowing equations..

a. HClO2(aq ) + NaIO(aq ) → HIO(aq ) + NaClO2(aq )

b. HS-(aq ) + HF(aq ) → H2S(aq ) + F-(aq )

. HS-(aq ) + OH-(aq ) → S2-(aq ) + H2O(l )

d. H3 AsO4(aq ) + 3NaOH(aq ) → Na3 AsO4(aq ) + 3H2O(l )

Solution

a. Te HClO2 loses an H+ ion, so it is the Brønsd-Lowry acid. Te IO- in

the NaIO gains the H+ ion, so the NaIO is the Brønsd-Lowry bas.

b. Te HF loses an H+ ion, so it is the Brønsd-Lowry acid. Te HS- gains

the H+

ion, so it is the Brønsd-Lowry bas.. Te HS- loses an H+ ion, so it is the Brønsd-Lowry acid. Te OH- gains

the H+ ion, so it is the Brønsd-Lowry bas.

d. Te H3 AsO4 loses three H+ ions, so it is the Brønsd-Lowry acid. EahOH- in NaOH gains an H+ ion, so the NaOH is the Brønsd-Lowry bas.

oBjeCtive 18

exerCise 8.6 - Brønsted-Lowry Acids and Bases

Identiy the Brønsted‑Lowry aid and base in eah o the ollowing equations..

a. HNO2(aq ) + NaBrO(aq ) → HBrO(aq ) + NaNO2(aq )

b. H2 AsO4-(aq ) + HNO2(aq ) H3 AsO4(aq ) + NO2

-(aq )

. H2 AsO4-(aq ) + 2OH-(aq ) → AsO4

3-(aq ) + 2H2O(l )

oBjeCtive 18

Arrhenius base A substane that produes hydroxide ions, OH-, when added to water.

Basic solution A solution with a signiant onentration o hydroxide ions, OH-.Strong base A substane that generates at least one hydroxide ion in solution or every

unit o substane added to water. Weak base A substane that produes ewer hydroxide ions in water solution than

partiles o the substane added. Neutralization reaction A hemial reation between an aid and a base.Brønsted‑Lowry acid‑base reaction A hemial reation in whih a proton, H+, is

transerred.Brønsted‑Lowry Acid A substane that donates protons, H+, in a Brønsted‑Lowry

aid‑base reation.Brønsted‑Lowry Base A substane that aepts protons, H+, in a Brønsted‑Lowry

aid‑base reation.

Chapter

Glossary



Chapter Objectives 36

Conjugate acid Te moleule or ion that orms when one H+ ion is added to a

moleule or ion.

Conjugate base Te moleule or ion that orms when one H+ ion is removed rom

a moleule or ion.

Conjugate acid‑base pair wo moleules or ions that dier by one H+ ion.

Amphoteric substance A substane that an at as either a Brønsted‑Lowry aid or aBrønsted‑Lowry base, depending on the irumstanes.

You can s yoursl on h glossary rms a h xbook’s Wb si.

Chapter ObjectivesTe goal of this chapter is to teach you to do the following.

1. Dene all o the terms in the Chapter Glossary.

Section 8.1 Strong and Weak Acids and Bases

2. Identiy ioni ompounds ontaining hydroxide ions as strong bases.3. Desribe the hanges that take plae when ammonia, NH3, is dissolved in water,

and use this desription to explain why ammonia is a weak Arrhenius base.4. Desribe the hanges that take plae when an ioni ompound ontaining

arbonate or hydrogen arbonate ions is dissolved in water, and use thisdesription to explain why these anions are weak Arrhenius bases.

5. Given a name or ormula or a substane, identiy it as either (1) an Arrheniusstrong aid, (2) an Arrhenius weak aid, (3) an Arrhenius strong base, or (4) an Arrhenius weak base.

Section 8.2 pH and Acidic and Basic Solutions6. Given the pH o a solution, identiy the solution as aidi, basi, or neutral.7. Given the pH o two aidi solutions, identiy whih solution is more aidi.8. Given the pH o two basi solutions, identiy whih solution is more basi.9. Desribe how litmus paper an be used in the laboratory to identiy whether a

solution is aidi or basi.

Section 8.3 Arrhenius Acid‑Base Reactions

10. Desribe the proess that takes plae at the moleular level or (a) a strong,monoproti aid, suh as HNO3, and an aqueous strong base, suh as NaOH, (b)a strong monoproti aid, suh as HCl(aq ), and an insoluble ioni ompound,suh as Al(OH)3, and () any monoproti aid and a solution ontainingarbonate ions or hydrogen arbonate ions. Your desription should inludemention o the partiles in solution beore and ater the reation. It should alsoinlude a desription o the proess that leads to the reation.

11. Given the names or ormulas or a monoproti or polyproti aid and an ioniompound ontaining hydroxide, arbonate, or hydrogen arbonate ions, writethe omplete balaned equation that desribes the neutralization reation thattakes plae between them.

12. Identiy H2O(l ) and CO2( g ) as the produts o the reation o an aid witharbonate, CO3

2-, or hydrogen arbonate, HCO3-.

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Section 8.4 Brønsted‑Lowry Acids and Bases

13. Explain why the Brønsted‑Lowry denitions or acid and base are oten used,

instead o the Arrhenius denitions, to desribe aid‑base reations.

14. Given a ormula or a moleule or ion, write the ormula or its onjugate aid.

15. Given a ormula or a moleule or ion, write the ormula or its onjugate base.

16. Explain why a substane an be a Brønsted‑Lowry aid in one reation and a

Brønsted‑Lowry base in a dierent reation. Give an example to illustrate your

explanation.

17. Explain why the Arrhenius denitions or acid and base , and not the Brønsted‑

Lowry denitions, are used to desribe whether an isolated substane is an aid or

base.

18. Given a Brønsted‑Lowry aid‑base equation, identiy the Brønsted‑Lowry aid

and Brønsted‑Lowry base.

Review

Questions

1. Dene the ollowing terms.

a. aqueous . double‑displaement reation

b. spetator ion d. net ioni equation

2. Write the name o the polyatomi ions represented by the ormulas CO32- and

HCO3-.

3. Write the ormulas or the polyatomi ions dihydrogen phosphate ion and aetateion.

4. Whih o the ollowing ormulas represents an ioni ompound?

a. MgCl2 d. Na2SO4

b. PCl3 e. H2SO3c. KHSO4

5. Write the names that orrespond to the ormulas KBr, Cu(NO3)2, and(NH4)2HPO4.

6. Write the ormulas that orrespond to the names nikel(II) hydroxide,ammonium hloride, and alium hydrogen arbonate.

7. Predit whether eah o the ollowing is soluble or insoluble in water.

a. iron(III) hydroxide . aluminum nitrate

b. barium sulate d. opper(II) hloride

8. Desribe how the strong monoproti aid hydrohlori aid, HCl ats when it isadded to water, inluding a desription o the nature o the partiles in solutionbeore and ater the reation with water. I there is a reversible reation with water, desribe the orward and the reverse reations.

9. Desribe how the weak monoproti aid aeti aid, HC2H3O2, ats when it isadded to water, inluding a desription o the nature o the partiles in solutionbeore and ater the reation with water. I there is a reversible reation with water, desribe the orward and the reverse reations.

10. Desribe the proess by whih the ioni ompound sodium hydroxide dissolvesin water.

11. Write the omplete equation or the preipitation reation that takes plae when water solutions o zin hloride and sodium phosphate are mixed.



Key Ideas 36

Key IdeasComplete the ollowing by writing one o these words or phrases in eah blank.

10‑old greater than 7aeptor higheradded hydroxide ions, OH-,amphoteri hydroxides

Arrhenius less than 7basi lowerblue neutralizeBrønsted‑Lowry redarbon dioxide, CO2, removeddonor strong basesdouble‑displaement transerewer water

12. Aording to the modern version o the Arrhenius theory o aids and bases, abase is a substane that produes _____________ when it is added to water.

13. A solution that has a signiant onentration o hydroxide ions is alled a(n)

_____________ solution.14. Compounds that ontain hydroxide ions are oten alled _____________.15. All water‑soluble hydroxides are _____________.16. A weak base is a base that produes _____________ hydroxide ions in water

solution than there are partiles o base dissolved.17. Aidi solutions have pH values _____________, and the more aidi a solution

is, the _____________ its pH. A hange o 1 pH unit refets a(n)_____________ hange in H3O+ ion onentration.

18. Basi solutions have pH values _____________, and the more basi the solutionis, the _____________ its pH.

19. Litmus, a natural dye, is derived rom lihen. It turns _____________ in aidi

onditions and _____________ in basi onditions.20. When an Arrhenius aid is ombined with an Arrhenius base, we say that they

_____________ eah other.21. When hydronium ions and hydroxide ions ollide in solution they reat to orm

_____________.22. Most Arrhenius neutralization reations, suh as the reation between nitri aid

and sodium hydroxide, are _____________ reations.23. Carboni aid is unstable in water, so when it orms in aqueous solutions, it

deomposes into _____________ and water, H2O(l ).24. A Brønsted‑Lowry aid is a proton (H+) _____________, a Brønsted‑Lowry base

is a proton _____________, and a Brønsted‑Lowry aid‑base reation is a proton_____________.25. Te onjugate aid o a moleule or ion is the moleule or ion that orms when

one H+ ion is _____________.26. Te onjugate base o a moleule or ion is the moleule or ion that orms when

one H+ ion is _____________.27. A substane that an at as either a Brønsted‑Lowry aid or a Brønsted‑Lowry

base, depending on the irumstanes, is alled a(n) _____________ substane.28. Te _____________ system is oten used to desribe spei aid‑base reations,

but the _____________ system is used to desribe whether isolated substanesare aids, bases, or neither.




Section 8.1 Strong and Weak Acids and Bases

29. Desribe the hanges that take plae when ammonia, NH3, is dissolved in water,

and use this desription to explain why ammonia is a weak Arrhenius base.

30. Classiy eah o these substanes as a weak aid, strong aid, weak base, or strong

base in the Arrhenius aid‑base sense.a. H2CO3 e. NH3

b. esium hydroxide . hlorous aid

. HF(aq ) g. HCl(aq )

d. sodium arbonate h. benzoi aid

31. Classiy eah o the substanes as a weak aid, strong aid, weak base, or strong

base in the Arrhenius aid‑base sense.

a. HNO3 e. H2SO4

b. ammonia . nitrous aid

. LiOH g. NaHCO3

d. phosphorous aid

Section 8.2 pH and Acidic and Basic Solutions

32. Classiy eah o the ollowing solutions as aidi, basi, or neutral.

a. omato juie with a pH o 4.53

b. Milk o magnesia with a pH o 10.4

. Urine with a pH o 6.8

33. Classiy eah o the ollowing solutions as aidi, basi, or neutral.

a. Saliva with a pH o 7.0

b. Beer with a pH o 4.712. A solution o a drain leaner with a pH o 14.0

34. Whih is more aidi, arbonated water with a pH o 3.95 or milk with a pH o

6.3?

35. Whih is more basi, a soap solution with a pH o 10.0 or human tears with a

pH o 7.4?

36. Identiy eah o the ollowing harateristis as assoiated with aids or bases.

a. tastes sour

b. turns litmus red

. reats with HNO3

37. Identiy eah o the ollowing properties as harateristi o aids or o bases.a. turns litmus blue

b. reats with arbonate to orm CO2( g )

Section 8.3 Arrhenius Acid‑Base Reactions

38. Desribe the proess that takes plae between the partiipants in the

neutralization reation between the strong aid hydrohlori aid, HCl(aq ),

and the strong base sodium hydroxide, NaOH(aq ), orming water and sodium

hloride, NaCl(aq ). Mention the nature o the partiles in the solution beore and

ater the reation.

Chapter

Problems

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oBjeCtive 5

oBjeCtive 5

oBjeCtive 6

oBjeCtive 10a

oBjeCtive 8

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Key Ideas 36


neutralization reation between the strong aid nitri aid, HNO3(aq ), and

the strong base potassium hydroxide, KOH(aq ), orming water and potassium

nitrate, KNO3(aq ). Mention the nature o the partiles in the solution beore and

ater the reation.

40. Desribe the proess that takes plae between the partiipants in theneutralization reation between the strong aid nitri aid, HNO3(aq ), and

water insoluble nikel(II) hydroxide, Ni(OH)2(s ), orming nikel(II) nitrate,

Ni(NO3)2(aq ), and water. Mention the nature o the partiles in the solution

beore and ater the reation.


neutralization reation between the strong aid hydrohlori aid, HCl(aq ), and

water insoluble hromium(III) hydroxide, Cr(OH)3(s ), orming hromium(III)

hloride, CrCl3(aq ), and water. Mention the nature o the partiles in the

solution beore and ater the reation.


neutralization reation between the strong aid hydrohlori aid, HCl(aq ), and

the weak base potassium arbonate, K 2CO3(aq ), orming water, arbon dioxide,

CO2( g ), and potassium hloride, KCl(aq ). Mention the nature o the partiles in

the solution beore and ater the reation.


neutralization reation between the strong aid nitri aid, HNO3(aq ), and the

weak base lithium hydrogen arbonate, LiHCO3(aq ), orming water, arbon

dioxide, CO2( g ), and lithium nitrate, LiNO3(aq ). Mention the nature o the

partiles in the solution beore and ater the reation.44. Write the omplete equation or the neutralization reations that take plae when

the ollowing water solutions are mixed. (I an aid has more than one aidi

hydrogen, assume that there is enough base to remove all o them. Assume that

there is enough aid to neutralize all o the basi hydroxide ions.)

a. HCl(aq ) + LiOH(aq )

b. H2SO4(aq ) + NaOH(aq )

. KOH(aq ) + HF(aq )

d. Cd(OH)2(s ) + HCl(aq )

45. Write the omplete equation or the neutralization reations that take plae when

the ollowing water solutions are mixed. (I an aid has more than one aidihydrogen, assume that there is enough base to remove all o them. Assume that

there is enough aid to neutralize all o the basi hydroxide ions.)

a. LiOH(aq ) + HNO2(aq )

b. Co(OH)2(s ) + HNO3(aq )

. H3PO4(aq ) + KOH(aq )

46. Write the omplete equation or the reation between HI(aq ) and water‑insoluble

solid CaCO3.

47. Write the omplete equation or the reation between HCl(aq ) and

water‑insoluble solid Al2(CO3)3.

oBjeCtive 10C

oBjeCtive 10B

oBjeCtive 10B

oBjeCtive 10a

oBjeCtive 11

oBjeCtive 11

oBjeCtive 10C

oBjeCtive 12

oBjeCtive 11

oBjeCtive 12

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Chapter Problems 36

60. For eah o the ollowing equations, identiy the Brønsted‑Lowry aid and base

or the orward reation.

a. 3NaOH(aq ) + H3PO4(aq ) → 3H2O(l ) + Na3PO4(aq )

b. HS-(aq ) + HIO3(aq ) → H2S(aq ) + IO3-(aq )

. HS-(aq ) + OH-(aq ) → S2-(aq ) + H2O(l )

61. Butanoi aid, CH3CH2CH2CO2H, is a monoproti weak aid that isresponsible or the smell o ranid butter. Write the ormula or the onjugate

base o this aid. Write the equation or the reation between this aid and water,

and indiate the Brønsted‑Lowry aid and base or the orward reation. (Te

aidi hydrogen atom is on the right side o the ormula.)

62. One o the substanes that give wet goats and dirty gym soks their harateristi

odors is hexanoi aid, CH3CH2CH2CH2CH2CO2H, whih is a monoproti

weak aid. Write the ormula or the onjugate base o this aid. Write the

equation or the reation between this aid and water, and indiate the Brønsted‑

Lowry aid and base or the orward reation. (Te aidi hydrogen atom is on

the right side o the ormula.)

63. Identiy the amphoteri substane in the ollowing equations.

HCl(aq ) + HS-(aq ) → Cl-(aq ) + H2S(aq )

HS-(aq ) + OH-(aq ) → S2-(aq ) + H2O(l )

64. Identiy the amphoteri substane in the ollowing equations.

HSO3-(aq ) + HF(aq ) H2SO3(aq ) + F-(aq )

NH3(aq ) + HSO3-(aq ) → NH4

+(aq ) + SO32-(aq )

Additional Problems

65. For eah o the ollowing pairs o ompounds, write the omplete equation or

the neutralization reation that takes plae when the substanes are mixed. (You

an assume that there is enough base to remove all o the aidi hydrogen atoms,

that there is enough aid to neutralize all o the basi hydroxide ions, and that

eah reation goes to ompletion.)

a. HBr(aq ) + NaOH(aq )

b. H2SO3(aq ) + LiOH(aq )

. KHCO3(aq ) + HF(aq )

d. Al(OH)3(s ) + HNO3(aq )66. For eah o the ollowing pairs o ompounds, write the omplete equation or

the neutralization reation that takes plae when the substanes are mixed. (You

an assume that there is enough base to remove all o the aidi hydrogen atoms,

that there is enough aid to neutralize all o the basi hydroxide ions, and that

eah reation goes to ompletion.)

a. Ni(OH)2(s ) + HBr(aq )

b. K 2CO3(aq ) + HC2H3O2(aq )

. HOCl(aq ) + NaOH(aq )

d. H3PO3(aq ) + KOH(aq )

oBjeCtive 18

oBjeCtive 12

oBjeCtive 11

oBjeCtive 12

oBjeCtive 11




67. Classiy eah o the ollowing substanes as aidi, basi, or neutral.

a. An apple with a pH o 2.9

b. Milk o Magnesia with a pH o 10.4

. Fresh egg white with a pH o 7.6

68. Classiy eah o the ollowing substanes as aidi, basi, or neutral.

a. A liquid detergent with a pH o 10.1b. Maple syrup with a pH o 7.0

. Wine with a pH o 3.2

69. Te pH o proessed heese is kept at about 5.7 to prevent it rom spoiling. Is

this aidi, basi, or neutral?

70. Is it possible or a weak aid solution to have a lower pH than a strong aid

solution? I so, how?

71. Te walls o limestone averns are omposed o solid alium arbonate. Te

ground water that makes its way down rom the surae into these averns is

oten aidi. Te alium arbonate and the H+ ions rom the aidi water reat

to dissolve the limestone. I this happens to the eiling o the avern, the eilingan ollapse, leading to what is alled a sinkhole. Write the net ioni equation or

the reation between the solid alium arbonate and the aqueous H+ ions.

72. Magnesium sulate, a substane used or reproong and paper sizing, is made

in industry rom the reation o aqueous suluri aid and solid magnesium

hydroxide. Write the omplete equation or this reation.

73. Manganese(II) phosphate is used to oat steel, aluminum, and other metals to

prevent orrosion. It is produed in the reation between solid manganese(II)

hydroxide and aqueous phosphori aid. Write the omplete equation or this

reation.

74. Te smell o Swiss heese is, in part, due to the monoproti weak aid propanoi

aid, CH3CH2CO2H. Write the equation or the omplete reation between this

aid and sodium hydroxide. (Te aidi hydrogen atom is on the right.)

75. Lati aid, CH3CH(OH)CO2H, is used in osmeti lotions, some o whih

laim to remove wrinkles. Te lati aid is thought to speed the removal o dead

skin ells. Write the equation or the omplete reation between this aid and

potassium hydroxide. (Te aidi hydrogen atom is on the right.)

76. Mali aid, HO2CCH2CH(OH)CO2H, is a diproti weak aid ound in apples

and watermelon. Write the equation or the omplete reation between this

aid and sodium hydroxide. (Te aidi hydrogen atoms are on eah end o the

ormula.)

77. One o the substanes used to make nylon is hexanedioi aid,HO2CCH2CH2CH2CH2CO2H. Tis diproti weak aid is also alled adipi

aid. Write the equation or the omplete reation between this aid and sodium

hydroxide. (Te aidi hydrogen atoms are on eah end o the ormula.)

78. For the ollowing equation, identiy the Brønsted‑Lowry aid and base or the

orward reation, and write the ormulas or the onjugate aid‑base pairs.

NaHS(aq ) + NaHSO4(aq ) → H2S( g ) + Na2SO4(aq )79. For the ollowing equation, identiy the Brønsted‑Lowry aid and base or the

orward reation, and write the ormulas or the onjugate aid‑base pairs.

HF(aq ) + NaHSO3(aq ) NaF(aq ) + H2SO3(aq )

oBjeCtive 6

oBjeCtive 6

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Chapter Problems 36

Discussion Problems

80. Assume you are given a water solution and told that it ontains either

hydrohlori aid or sodium hloride. Desribe how you ould determine whih

o these is present.

81. Assume that you are given a water solution that ontains either sodium

hydroxide or sodium hloride. Desribe how you ould determine whih is in

solution.

82. Assume that you are given a water solution that ontains either sodium

arbonate or sodium hydroxide. Desribe how you ould determine whih is in

solution.

Documents

Unit 4 Acids and Bases Text