ACIDS, ACIDS, BASES, AND pH, AND pH

2

An acid -------> H+ in waterAn acid -------> H+ in water

Arrhenius ACIDSArrhenius ACIDSArrhenius ACIDSArrhenius ACIDS

HCl(aq) ---> H+(aq) + Cl-(aq)

3

Base ---> OH- in waterBase ---> OH- in water

Arrhenius BASESArrhenius BASES

NaOH(aq) ---> NaNaOH(aq) ---> Na++(aq) + OH(aq) + OH--(aq)(aq)

NaOH is a NaOH is a strong basestrong base

Arrhenius TheoryArrhenius TheoryAcids HAcids H++

(hydrogen ions) in water

HHCl → Cl → HH++ + Cl + Cl--

Bases OHBases OH-- (hydroxide ions) (hydroxide ions) in waterNaNaOHOH → Na → Na++ + + OHOH--

D7C20

Arrhenius TheoryArrhenius Theory Substances ionize in Substances ionize in

waterwaterAcids, bases, and salts Acids, bases, and salts when dissolved in water, when dissolved in water, will will conduct electricityconduct electricity..

Called ElectrolytesCalled Electrolytes

6

The solutions conduct electricity!They are called

ELECTROLYTES

HCl, MgCl2, and NaCl are strong

electrolytes. They dissociate completely (or

nearly so) into ions.

Aqueous SolutionsAqueous SolutionsHow do we know ions are present?

7

An acid -------> HAn acid -------> H++ in water in waterAn acid -------> HAn acid -------> H++ in water in water

ACIDSACIDSACIDSACIDS

Some Some strongstrong acids areacids are

HClHCl hydrochlorichydrochloric

HH22SOSO44 sulfuricsulfuric

HClOHClO44 perchloricperchloric

HNOHNO33 nitricnitricHNOHNO33

Strong Acids will completely ionize

9

Aqueous SolutionsAqueous Solutions

weak electrolyte,like Acetic acid, ionizes only

to a small extent,

CHCH33COCO22H(aq) H(aq)

CHCH33COCO22--(aq) + H(aq) + H++(aq)(aq)

10

Weak AcidsWeak AcidsWeak AcidsWeak AcidsWeak electrolytes

CHCH33COCO22HH acetic acidacetic acid

HH22COCO33 carbonic acid carbonic acid

HH33POPO44 phosphoric acid phosphoric acid

HF hydrofluoric acidHF hydrofluoric acid

Acetic acid

11

Know the strong Know the strong acids & bases!acids & bases!

12

Aqueous SolutionsAqueous SolutionsSome compounds dissolve

in water but do not conduct electricity. They

are called

nonelectrolytes..

Examples include:Examples include:sugarsugarethanolethanolethylene glycolethylene glycol

Examples include:Examples include:sugarsugarethanolethanolethylene glycolethylene glycol

Hydrogen ions in waterHydrogen ions in water= Hydronium ions= Hydronium ions

14Ammonia, NHAmmonia, NH33

An Important Base

1515

ACID-BASE THEORIESACID-BASE THEORIESACID-BASE THEORIESACID-BASE THEORIES

• The most general theory for common aqueous acids and bases

is the BRØNSTED - LOWRY theory

•ACIDS DONATE H+ IONS

•BASES ACCEPT H+ IONS

Bronsted Bronsted BaseBase: adds : adds one one hydrogen ionhydrogen ion

Bronsted Bronsted AcidAcid: removes : removes oneone hydrogen ion hydrogen ion

Reactants Products

Chemical Reactions: New products are formed

Brønsted-Lowry TheoryBrønsted-Lowry Theory HCl + HHCl + H22O → HO → H33OO++ + Cl + Cl--

acid base C.A. C.B.acid base C.A. C.B. Conjugate acidConjugate acid –the PRODUCT –the PRODUCT

obtained after a BASE gains a obtained after a BASE gains a proton (hydrogen ion)proton (hydrogen ion)

Conjugate baseConjugate base –the PRODUCT –the PRODUCT obtained after an ACID donates a obtained after an ACID donates a proton (hydrogen ion)proton (hydrogen ion)

1919

2020

Conjugate PairsConjugate Pairs

Amphoteric Amphoteric

A substance having A substance having the ability to act as the ability to act as an acid or a basean acid or a baseor AmphoPROTICor AmphoPROTIC

Hydrogen ion = protonHydrogen ion = proton

Water is amphoproticWater is amphoprotic

It can gain and It can gain and lose a H+lose a H+

Why is Water Neutral?Why is Water Neutral?

When one water gains, When one water gains, another loses a H+another loses a H+

[H[H33O+ ] = [OH-]O+ ] = [OH-]

Brønsted-Lowry Theory Brønsted-Lowry Theory D7C20D7C20

ACIDACID: any substance that : any substance that donatesdonates a proton (hydrogen ion) a proton (hydrogen ion)

BASEBASE: any substance that : any substance that acceptsaccepts a proton (hydrogen ion)a proton (hydrogen ion)

MUST MUST occur together; Can not occur together; Can not gain unless something else losesgain unless something else loses

You PracticeYou PracticeNHNH33 + H + H22O → NHO → NH44

++ + OH + OH--

HNOHNO33 + NaOH → H + NaOH → H22O + NaNOO + NaNO33

NaHCONaHCO33 + HCl → NaCl + H + HCl → NaCl + H22COCO33

28

Acid- Base Acid- Base REACTIONSREACTIONSAcid- Base Acid- Base

REACTIONSREACTIONS

EXCHANGEEXCHANGEGas-FormingGas-FormingReactionsReactions

EXCHANGEEXCHANGE:: Precipitation Reactions Precipitation Reactions

REACTIONSREACTIONS REDOXREDOXReactionsReactions

REDOXREDOXReactionsReactions

29

ACIDSACIDSACIDSACIDSNonmetal oxides can be acids

CO2(aq) + H2O(liq)--->H2CO3(aq)

SO3(aq) + H2O(liq) ---> H2SO4(aq)

and can come from

burning coal and oil.

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BASESBASES

Metal oxides are bases

CaO(s) + H2O(liq)

--> Ca(OH)2(aq)

CaO in water. Indicator shows solution is basic.

31

Acid-Base ReactionsAcid-Base Reactions

• sometimes called NEUTRALIZATIONS because the solution is neither acidic nor

basic at the end.

• The other product of the A-B reaction is a

SALT, MX.

HX + MOH ---> MX + H2O

Mn+ comes from base & Xn- comes from acid

This is one way to make compounds!

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Acid-Base ReactionsAcid-Base Reactions The “driving force” is the

formation of water.

NaOH(aq) + HCl(aq) ---> NaCl(aq) + H2O(liq)

Net ionic equation

OH-(aq) + H+(aq) ---> H2O(liq)

This applies to ALL reactions of

STRONG acids and bases.