14.1 Arrhenius Definition14.1 Arrhenius Definition Acids produce hydrogen ions Acids produce hydrogen ions (H(H++) in aqueous solution.) in aqueous solution.

Bases produce hydroxide ions Bases produce hydroxide ions (OH(OH--) when dissolved in ) when dissolved in water.water.

Limits to aqueous solutions.Limits to aqueous solutions. Only one kind of base.Only one kind of base. NHNH33 ammonia could not be an ammonia could not be an

Arrhenius base.Arrhenius base.

Bronsted-Lowry DefinitionsBronsted-Lowry Definitions And acid is an proton (HAnd acid is an proton (H++) donor ) donor and a base is a proton acceptor.and a base is a proton acceptor.

Acids and bases always come in Acids and bases always come in pairs.pairs.

HCl is an acid.HCl is an acid. When it dissolves in water it When it dissolves in water it gives its proton to water.gives its proton to water.

HCl(g) + HHCl(g) + H22O(l) O(l) HH33OO++ + Cl + Cl--

In this equilibrium, water is a In this equilibrium, water is a base, makes hydronium ion.base, makes hydronium ion.

(YDVD)(YDVD)

QuickTime™ and aCinepak Codec by Radius decompressor

are needed to see this picture.

Conjugate Acid/Base Conjugate Acid/Base PairsPairs HA(aq) + HHA(aq) + H22O(l) O(l) H H33OO

++(aq) + A(aq) + A--(aq)(aq) Acid + Base Acid + Base Conjugate acid +Conjugate acid +

Conjugate base Conjugate base Conjugate baseConjugate base: everything that : everything that remains of the acid molecule after a remains of the acid molecule after a proton is lost.proton is lost.

Conjugate acidConjugate acid: formed when the proton : formed when the proton is transferred to the base.is transferred to the base.

This is an equilibrium.This is an equilibrium. Competition for HCompetition for H+ + between Hbetween H22O and AO and A--

The stronger base controls direction.The stronger base controls direction. If HIf H22O is a stronger base it takes the HO is a stronger base it takes the H++ Equilibrium moves to right.Equilibrium moves to right.

PracticePracticeIdentify the acid, base, Identify the acid, base, conjugate acid, conjugate base conjugate acid, conjugate base in the following reactions.in the following reactions.#32#32

HONHHONH33 + H + H22OO HONHHONH22-- + H + H33OO++

HOCl + CHOCl + C66HH55NHNH22 OCl OCl-- + C + C66HH55NHNH33++

Acid Dissociation Constant KAcid Dissociation Constant Kaa The equilibrium constant for the The equilibrium constant for the general equation.general equation.

HA(aq) + HHA(aq) + H22O(l) O(l) H H33OO++(aq) + (aq) +

AA--(aq)(aq)

KKaa = [H = [H33OO++][A][A--]]

[HA][HA] (YDVD)(YDVD)HH33OO

++ is often is often

written Hwritten H++ ignoring the ignoring the water in equation water in equation (it is implied).(it is implied).

QuickTime™ and aCinepak Codec by Radius decompressor

are needed to see this picture.

Acid dissociation constant KAcid dissociation constant Kaa HA(aq) HA(aq) HH++(aq) + A(aq) + A--(aq)(aq)

KKaa = [H = [H++][A][A--]]

[HA] [HA] We can write the expression for We can write the expression for any acid.any acid.

Strong acids dissociate Strong acids dissociate completely.completely.

Equilibrium far to right.Equilibrium far to right. Conjugate base is therefore weak. Conjugate base is therefore weak.

PracticePracticeWrite the dissociation Write the dissociation reaction and the corresponding reaction and the corresponding Ka equilibrium expression for Ka equilibrium expression for the following acids in water. the following acids in water. #30#30

HCHC22HH33OO22

CHCH33NHNH33++

Co(HCo(H22O)O)663+3+

14.2 Acid Strength14.2 Acid Strength Strong acidsStrong acids

KKaa is largeis large

[H[H++] is equal to ] is equal to [HA][HA]

AA-- is a weaker is a weaker base than waterbase than water

Weak acidsWeak acids

KKaa is smallis small

[H[H++] <<< [HA]] <<< [HA] AA-- is a stronger is a stronger base than waterbase than water

Strong Acids:Strong Acids:HBr, HCl, HIHBr, HCl, HIHNOHNO33, HClO, HClO33, HClO, HClO44, H, H22SOSO44, HIO, HIO33

Weak AcidsWeak Acids Its equilibrium lies far to Its equilibrium lies far to the left. the left. (CH(CH33COOH)COOH)

Yields a much stronger (it is Yields a much stronger (it is relatively strong) conjugate relatively strong) conjugate base than water. base than water. (CH(CH33COOCOO))

(YDVD)(YDVD)

Types of AcidsTypes of Acids Monoprotic - One acidic proton.Monoprotic - One acidic proton. Polyprotic Acids - more than 1 Polyprotic Acids - more than 1 acidic hydrogen (diprotic, acidic hydrogen (diprotic, triprotic).triprotic).

Oxyacids - Proton is attached Oxyacids - Proton is attached to the oxygen of an ion.to the oxygen of an ion.

Organic acids contain the Organic acids contain the Carboxyl group -COOH with the H Carboxyl group -COOH with the H attached to Oattached to O

Generally very weak.Generally very weak.

Water as an Acid and a Water as an Acid and a BaseBase

Wateris amphoteric - it behave as both Wateris amphoteric - it behave as both an acid and a base. Water also an acid and a base. Water also autoionizes. autoionizes. (BDVD)(BDVD)

2H2H22O(l) O(l) HH33OO++(aq) + OH(aq) + OH--(aq)(aq)

KKWW= [H= [H33OO++][OH][OH--] = [H] = [H++][OH][OH--]]

At 25ºC KAt 25ºC KWW = 1.0 x10 = 1.0 x10-14-14

In In EVERYEVERY aqueous solution. aqueous solution. Neutral solution [HNeutral solution [H++] = [OH] = [OH--] = 1.0 x10] = 1.0 x10-7-7 Acidic solution [HAcidic solution [H++] > [OH] > [OH--]] Basic solution [HBasic solution [H++] < [OH] < [OH--]]

PracticePractice Order the following from Order the following from strongest to weakest acid.strongest to weakest acid.

HH22OO HClHCl HOCHOC66HH55 Ka = 1.6 x 10Ka = 1.6 x 10-10-10 HFHF Ka = 7.2 x 10Ka = 7.2 x 10-4-4

Practice Practice #38#38

Which is the stronger base?Which is the stronger base? ClCl-- or H or H22OO

HH22O or NOO or NO22--

CNCN-- or OC or OC66HH55--

HNOHNO22 Ka = 4.0 x 10Ka = 4.0 x 10-4-4

HCNHCN Ka = 6.2 x 10Ka = 6.2 x 10-10-10

HOCHOC66HH55 Ka = 1.6 x 10 Ka = 1.6 x 10-10-10

PracticePractice Calculate [H+] or [OH-] for each of the Calculate [H+] or [OH-] for each of the

following solutions at 25°C and state following solutions at 25°C and state whether the solution is neutral, whether the solution is neutral, acidic, or basic. acidic, or basic. Ex.14.3Ex.14.3

1.1. 1.0 x 101.0 x 10-5-5 M OH M OH--

2.2. 1.0 x 101.0 x 10-7-7 M OH M OH--

3.3. 10.0 M H10.0 M H++

4.4. At 60°C, KAt 60°C, Kww is 1 x 10 is 1 x 10-13-13 Ex.14.4Ex.14.4

5.5. Using LeChatelier’s principle, predict Using LeChatelier’s principle, predict whether the reactionwhether the reaction

2H2H22O(l) O(l) HH33OO++(aq) + OH(aq) + OH--(aq) is (aq) is exothermic or endothermic.exothermic or endothermic.

n Calculate [H+] and [OH-] in a neutral Calculate [H+] and [OH-] in a neutral solution at 60°C.solution at 60°C.

14.3 The pH Scale14.3 The pH Scale pH= -log[HpH= -log[H++]] Used because [HUsed because [H++] is usually very ] is usually very smallsmall

As pH decreases, [HAs pH decreases, [H++] increases ] increases exponentiallyexponentially

Sig. figs - only the digits after Sig. figs - only the digits after the decimal place of a pH are the decimal place of a pH are significantsignificant

[H[H++] = 1.0 x 10] = 1.0 x 10-8-8 pH= 8.00 2 sig pH= 8.00 2 sig figsfigs

pOH= -log[OHpOH= -log[OH--]] pKa = -log KpKa = -log K

RelationshipsRelationships KKWW = [H = [H++][OH][OH--]] -log K-log KWW = -log([H = -log([H++][OH][OH--])]) -log K-log KWW = -log[H = -log[H++]+ -log[OH]+ -log[OH--]] pKpKWW = pH + pOH = 14.00 = pH + pOH = 14.00 KKWW = 1.0 x10 = 1.0 x10-14-14

14.00 = pH + pOH14.00 = pH + pOH [H[H++],[OH],[OH--],pH and pOH],pH and pOHGiven any one of these we can Given any one of these we can find the other three.find the other three.

Basic

Acidic Neutral

100

10-

1

10-

3

10-

5

10-

7

10-

9

10-

11

10-

13

10-

14

[H+]

0 1 3 5 7 9 11

13

14

pH

Basic

100

10-

1

10-

3

10-

5

10-

7

10-

9

10-

11

10-

13

10-

14

[OH-

]

01357911

13

14

pOH

Practice Practice Ex. 14.5Ex. 14.5

Calculate the pH and pOH for each solution at 25°C.

A) 1.0 x 10-3 M OH-

B) 1.0 M H+

C) 2.5 x 10-2 M H+

PracticePractice Calculate the [H+] and [OH-] for each solution at 25°C. Identify each solution as acidic, basic or neutral.

pH= 3.20 pH=11.2 pOH= 9.6

PracticePractice The pH of ammonia was The pH of ammonia was

measured to be 11.89 at measured to be 11.89 at 25°C. Calculate the pOH, 25°C. Calculate the pOH, [H[H++], [OH], [OH--] for the sample.] for the sample.

The pH of a sample of human The pH of a sample of human blood was measured to be blood was measured to be 7.41 at 25°C. Calculate the 7.41 at 25°C. Calculate the pOH, [HpOH, [H++], [OH], [OH--] for the ] for the sample. sample. Ex. 14.6Ex. 14.6

14.4 Calculating pH of Solutions14.4 Calculating pH of Solutions Always write down the major Always write down the major ions in solution.ions in solution.

Remember these are Remember these are equilibria.equilibria.

Remember the chemistry.Remember the chemistry. Don’t try to memorize there Don’t try to memorize there is no one way to do this. is no one way to do this. Read p. 665. Very important!Read p. 665. Very important!

Strong AcidsStrong Acids ALWAYS WRITE THE MAJOR ALWAYS WRITE THE MAJOR SPECIES.SPECIES.

Completely dissociated.Completely dissociated. [H[H++] = [HA]] = [HA] [OH[OH--] is going to be small ] is going to be small because of equilibrium.because of equilibrium.

1010-14-14 = [H = [H++][OH][OH--]] If [HA]< 10If [HA]< 10-7-7 water water contributes Hcontributes H++

Practice Practice #49#49

A solution is prepared by A solution is prepared by mixing 50.0 mL of 0.050 M HCl mixing 50.0 mL of 0.050 M HCl and 1500.0 mL of 0.10 M HNOand 1500.0 mL of 0.10 M HNO33. . Water is added until the Water is added until the final volume is 1.00 L. final volume is 1.00 L. Calculate [HCalculate [H++], [OH], [OH--] and the ] and the pH for this solution. pH for this solution.

Practice Practice #50 (WA)#50 (WA)

A solution is prepared by A solution is prepared by mixing 90.0 mL of 5.00 M HCl mixing 90.0 mL of 5.00 M HCl and 30.0 mL of 8.00 M HNOand 30.0 mL of 8.00 M HNO33. . Water is added until the Water is added until the final volume is 1.00 L. final volume is 1.00 L. Calculate [HCalculate [H++], [OH], [OH--] and the ] and the pH for this solution. pH for this solution.

14.5 Weak Acids14.5 Weak Acids Ka will be small.Ka will be small. List major species in solution.List major species in solution. Choose species that can produce HChoose species that can produce H++ and write reactions.and write reactions.

Based on K values, decide on Based on K values, decide on dominant equilibrium.dominant equilibrium.

Write equilibrium expression for Write equilibrium expression for dominant equilibrium.dominant equilibrium.

List initial concentrations in List initial concentrations in dominant equilibrium.dominant equilibrium.

Weak AcidsWeak Acids Define change at equilibrium (as Define change at equilibrium (as ““xx”).”).

Write equilibrium concentrations Write equilibrium concentrations in terms of in terms of xx..

Substitute equilibrium Substitute equilibrium concentrations into equilibrium concentrations into equilibrium expression.expression.

Solve for Solve for xx the “easy way.” the “easy way.”

Verify assumptions using 5% rule.Verify assumptions using 5% rule.

Calculate [HCalculate [H++] and pH.] and pH.

PracticePractice Calculate the pH of 0.100 M Calculate the pH of 0.100 M hypochlorous acid, HOCl, hypochlorous acid, HOCl,

with a Ka = 3.5 x10with a Ka = 3.5 x10-8-8 Ex.14.8Ex.14.8

Calculate the pH of 2.0 M Calculate the pH of 2.0 M

acetic acid, HCacetic acid, HC22HH33OO22,, with a with a

Ka = 1.8 x10Ka = 1.8 x10-5-5.. What is the What is the pOH, [OHpOH, [OH--], and [H], and [H++]?]?

How about a quadratic? How about a quadratic? #57#57

Calculate the pH of 0.020 M Calculate the pH of 0.020 M HF solution, with a Ka = 7.2 HF solution, with a Ka = 7.2

x10x10-4-4.. What is the pOH, [OHWhat is the pOH, [OH--], ], and [Hand [H++]?]?

A mixture of Weak AcidsA mixture of Weak Acids The process is the same.The process is the same. Determine the major species.Determine the major species. The stronger will predominate.The stronger will predominate. Bigger Ka if concentrations are Bigger Ka if concentrations are comparablecomparable

Calculate the pH of a mixture Calculate the pH of a mixture 1.00 M HCN (Ka = 6.2 x 101.00 M HCN (Ka = 6.2 x 10-10-10) and ) and 5.00 M HNO5.00 M HNO22 (Ka = 4.0 x 10 (Ka = 4.0 x 10-4-4). ).

What is the concentration of the What is the concentration of the CNCN-- ion in this solution at ion in this solution at equilibrium. equilibrium. EX. 14.9EX. 14.9

Percent dissociationPercent dissociation = = amount dissociated amount dissociated x 100 x 100 initial concentration initial concentration

For a weak acid percent dissociation For a weak acid percent dissociation increases as acid becomes more increases as acid becomes more dilute.dilute.

Calculate the % dissociation of Calculate the % dissociation of 1.00 M 1.00 M and .00100 M Acetic acidand .00100 M Acetic acid (Ka = (Ka = 1.8 x 101.8 x 10-5-5

As [HA]As [HA]00 decreases [H decreases [H++] decreases ] decreases

but % dissociation increases.but % dissociation increases. Le ChatelierLe Chatelier

Calculating KaCalculating Ka What is the KWhat is the Kaa of lactic acid of lactic acid (HC(HC33HH55OO33) that is 3.7 % ) that is 3.7 % dissociated as 0.100 M solution? dissociated as 0.100 M solution? Ex. 14.11Ex. 14.11

A 0.15 M solution of a weak A 0.15 M solution of a weak acid, is 3.0% dissociated. acid, is 3.0% dissociated. Calculate KCalculate Kaa #65#65

The pH of a 1.00 x 10The pH of a 1.00 x 10-2-2 M M solution of cyanic acid (HOCN) solution of cyanic acid (HOCN) is 2.77 at 25°C. Calculate Kis 2.77 at 25°C. Calculate Kaa for HOCN from this result. for HOCN from this result. #67#67

Calculating KaCalculating KaWAWA In a 0.100 M solution of HF, In a 0.100 M solution of HF, the percent dissociation is the percent dissociation is 8.1%. Calculate the K8.1%. Calculate the Kaa #66#66

A 0.050M solution of A 0.050M solution of trichloroacetic acid (CCltrichloroacetic acid (CCl33COCO22H) H) is the same pH as 0.040M HClOis the same pH as 0.040M HClO44 solution. Caculate the Ksolution. Caculate the Kaa for for trichloroacetic acid. trichloroacetic acid. #68#68

14.6 Bases14.6 Bases The OHThe OH-- is a strong base. is a strong base. Hydroxides of the alkali metals Hydroxides of the alkali metals are strong bases because they are strong bases because they dissociate completely when dissociate completely when dissolved.dissolved.

The hydroxides of alkaline earths The hydroxides of alkaline earths Ca(OH)Ca(OH)22 etc. are strong dibasic etc. are strong dibasic

bases, but they don’t dissolve bases, but they don’t dissolve well in water.well in water.

Used as antacids because [OHUsed as antacids because [OH-- ] ] can’t build up.can’t build up.

Bases without OHBases without OH--

Bases are proton acceptors.Bases are proton acceptors.

NHNH33 + H + H22O O NHNH44++ + OH + OH--

It is the lone pair on nitrogen It is the lone pair on nitrogen that accepts the proton.that accepts the proton.

Many weak bases contain NMany weak bases contain N BB(aq) (aq) + H+ H22O(l)O(l) BH BH++(aq) (aq) + OH+ OH- -

(aq)(aq)

KKbb = [ = [BHBH++][][OHOH- - ]]

[ [BB] ]

Strength of BasesStrength of Bases Hydroxides are strong.Hydroxides are strong. Calculate the pH of a 5.0 x 10Calculate the pH of a 5.0 x 10-2 -2 M NaOH M NaOH solution solution Ex. 14.12Ex. 14.12

Calculate the pH, [OH] and pOH of a 4.0 Calculate the pH, [OH] and pOH of a 4.0 x 10x 10-4 -4 M Ca(OH)M Ca(OH)22 solution. solution. #78a#78a

Calculate the concentration of of an Calculate the concentration of of an aqueous Sr(OH)aqueous Sr(OH)22 solution that has a pH solution that has a pH of 10.5 of 10.5 #82#82

Others are weakOthers are weak.. Smaller Smaller KKbb - weaker - weaker base.base.

Which is the stronger base:Which is the stronger base: NHNH33 or Cl or Cl--

NHNH33 or C or C55HH55NN

Practice: weak basePractice: weak base Calculate the pH of 15.0 M Calculate the pH of 15.0 M ammonia NHammonia NH33 with a K with a Kbb = 1.8 = 1.8

x10x10-5-5 Ex. 14.13Ex. 14.13

Calculate the pH of 1.0 M Calculate the pH of 1.0 M methylamine with a Kmethylamine with a Kb b == 4.38 4.38

x10x10-4 -4 Ex. 14.14Ex. 14.14

Calculate the [OHCalculate the [OH--], [H], [H++], and ], and pH of 0.20 M pyridine with a pH of 0.20 M pyridine with a KKb b == 1.7x101.7x10-9 -9

#86b#86b

14.7 Polyprotic acids14.7 Polyprotic acids Always dissociate stepwise.Always dissociate stepwise. The first HThe first H++ comes off much comes off much easier than the second.easier than the second.

Ka for the first step is much Ka for the first step is much bigger than Ka for the bigger than Ka for the second.second.

Denoted KaDenoted Ka11, Ka, Ka22, Ka, Ka33

Polyprotic acidPolyprotic acid HH22COCO33 HH++ + HCO + HCO33

--

KaKa11= 4.3 x 10= 4.3 x 10-7-7

HCOHCO33-- HH++ + CO + CO33

-2-2

KaKa22= 5.6 x 10= 5.6 x 10-11-11

Base in first step is acid in Base in first step is acid in second.second.

In calculations we can In calculations we can normally ignore the second normally ignore the second dissociation.dissociation.

Calculate the ConcentrationCalculate the Concentration Calculate the pH of a 5.00 M Calculate the pH of a 5.00 M

Phosphoric acid, HPhosphoric acid, H33POPO44,,

solution and the equilibrium solution and the equilibrium concentrations of each concentrations of each species. species. Ex. 14.15Ex. 14.15

KaKa11 = 7.5 x 10 = 7.5 x 10-3-3

KaKa22 = 6.2 x 10 = 6.2 x 10-8-8

KaKa33 = 4.8 x 10 = 4.8 x 10-10-10

Sulfuric acid is specialSulfuric acid is special In the first step, it is a strong In the first step, it is a strong acid.acid.

In the second step, KaIn the second step, Ka22 = 1.2 x 10 = 1.2 x 10-2-2

For solutions more dilute than 1.0 For solutions more dilute than 1.0 M, the dissociation of HSOM, the dissociation of HSO44

-- is is important. Solving requires the important. Solving requires the quadratic equation.quadratic equation.

Calculate the pH in a 1.0 M Calculate the pH in a 1.0 M solution of Hsolution of H22SOSO4 4 Ex. 14.16Ex. 14.16

Calculate the pH in a 1.0 x 10Calculate the pH in a 1.0 x 10-2-2 M M solution of Hsolution of H22SOSO4 4 Ex. 14.17Ex. 14.17

14.8 Salts as acids and bases14.8 Salts as acids and bases Salts are ionic compounds.Salts are ionic compounds. Salts of the cation of strong Salts of the cation of strong bases and the anion of strong bases and the anion of strong acids are neutral.acids are neutral.

For example NaCl, KNOFor example NaCl, KNO33

There is no equilibrium for There is no equilibrium for strong acids and bases.strong acids and bases.

We ignore the reverse We ignore the reverse reaction.reaction.

Basic SaltsBasic Salts If the anion of a salt is the If the anion of a salt is the conjugate base of a weak acid, a conjugate base of a weak acid, a basic solution will be generated.basic solution will be generated.

In an aqueous solution of NaFIn an aqueous solution of NaF The major species are NaThe major species are Na++, F, F--, and H, and H22OO

FF- - + H+ H22O O HF + OHHF + OH--

KKbb =[HF][OH=[HF][OH--]]

[F [F- - ]]

but Ka = [Hbut Ka = [H++][F][F--]] = 7.2 x 10= 7.2 x 10-4 -4

[HF] [HF]

Basic SaltsBasic Salts KKaa x K x Kb b = [HF][OH= [HF][OH--]] x [Hx [H++]]

[F[F--]] [F[F- - ] ] [HF][HF]

Basic SaltsBasic Salts KKaa x K x Kb b = [HF][OH= [HF][OH--]] x [Hx [H++]]

[F[F--]] [F[F- - ] ] [HF][HF]

Basic SaltsBasic Salts KKaa x K x Kb b = [HF][OH= [HF][OH--]] x [Hx [H++]]

[F[F--]] [F[F- - ] ] [HF][HF]

Basic SaltsBasic Salts KKaa x K x Kb b = [HF][OH= [HF][OH--]] x [Hx [H++]]

[F[F--]] [F[F- - ] ] [HF][HF]

KKaa x K x Kb b =[OH=[OH--] [H] [H++]]

Basic SaltsBasic Salts KKaa x K x Kb b = [HF][OH= [HF][OH--]] x [Hx [H++]]

[F[F--]] [F[F- - ] ] [HF][HF]

KKaa x K x Kb b =[OH=[OH--] [H] [H++]]

KKaa x K x Kb b = K= KWW Calculate the pH of a 0.30 M Calculate the pH of a 0.30 M NaF solution. The KNaF solution. The Kaa for HF for HF is 7.2 x 10is 7.2 x 10-4 -4

Ex. 14.18Ex. 14.18

KKaa tells us K tells us Kbb The anion of a weak acid is a weak The anion of a weak acid is a weak base.base.

Calculate the pH of a solution of Calculate the pH of a solution of 1.00 M NaCN. Ka of HCN is 6.2 x 101.00 M NaCN. Ka of HCN is 6.2 x 10-10-10

The CNThe CN-- ion competes with OH ion competes with OH-- for the H for the H++

Which is the stronger acid NHWhich is the stronger acid NH44++ or or

CHCH33NHNH33++? (NH? (NH3 3 :: KKbb= 1.8x10= 1.8x10-5-5

CHCH33NHNH22 :K :Kbb=4.4x10=4.4x10-4-4) ) #102#102

Arrange the following solutions in Arrange the following solutions in order of most acidic to most basic. order of most acidic to most basic. KOH, KCl, KCN, NHKOH, KCl, KCN, NH44Cl, HCl Cl, HCl #99#99

Acidic saltsAcidic salts A salt with the cation of a weak A salt with the cation of a weak base and the anion of a strong base and the anion of a strong acid will be acidic.acid will be acidic.

The same development as bases The same development as bases leads to Kleads to Kaa x K x Kb b = K= KWW

Calculate the pH of a solution Calculate the pH of a solution of 0.10 M NHof 0.10 M NH44Cl (the KCl (the Kbb of NH of NH33 1.8 x 101.8 x 10-5-5). ). Ex. 14.19Ex. 14.19

Other acidic salts are those of Other acidic salts are those of highly charged metal ions.(Alhighly charged metal ions.(Al3+3+))

More on this later.More on this later.

Salts with Acidic and Basic ionsSalts with Acidic and Basic ions KKaa > K > Kb b acidicacidic KKaa < K < Kb b basicbasic KKaa = K = Kb b neutralneutral Predict whether an aqueous Predict whether an aqueous solution of each of the following solution of each of the following salts will be acidic, basic or salts will be acidic, basic or neutral. neutral. EX.14.21EX.14.21

NHNH44CC22HH33OO22

NHNH44CNCN AlAl22(SO(SO44))33

#105 in Text.#105 in Text.

14.9 Structure and Acid-Base 14.9 Structure and Acid-Base PropertiesProperties

Any molecule with an H in it is a Any molecule with an H in it is a potential acid.potential acid.

The stronger the X-H bond the less The stronger the X-H bond the less acidic (compare bond dissociation acidic (compare bond dissociation energies).energies).

The more polar the X-H bond the The more polar the X-H bond the stronger the acid (use stronger the acid (use electronegativities).electronegativities).

The more polar H-O-X bond - stronger The more polar H-O-X bond - stronger acid.acid.

Strength of oxyacidsStrength of oxyacids The more oxygen hooked to the The more oxygen hooked to the central atom, the more acidic central atom, the more acidic the hydrogen.the hydrogen.

HClOHClO44 > HClO > HClO33 > HClO > HClO22 > HClO > HClO

Remember that the H is attached Remember that the H is attached to an oxygen atom.to an oxygen atom.

The oxygen’s are The oxygen’s are electronegativeelectronegative

Pull electrons away from Pull electrons away from hydrogenhydrogen

Strength of oxyacidsStrength of oxyacids

Electron Density

Cl

O H

Strength of oxyacidsStrength of oxyacids

Electron Density

Cl

O HO

Strength of oxyacidsStrength of oxyacids

Cl

O H

O

O

Electron Density

Strength of oxyacidsStrength of oxyacids

Cl

O H

O

O

O

Electron Density

Hydrated metalsHydrated metals Highly charged Highly charged metal ions metal ions pull the pull the electrons of electrons of surrounding surrounding water water molecules molecules toward them.toward them.

Make it easier Make it easier for Hfor H++ to come to come off.off.

Al+3 OH

H

14.10 Acid-Base Properties of 14.10 Acid-Base Properties of OxidesOxides

Non-metal oxides dissolved in Non-metal oxides dissolved in water can make acids.water can make acids.

SOSO33 (g) + H (g) + H22O(l) O(l)

HH22SOSO44(aq)(aq)

Ionic oxides dissolve in water Ionic oxides dissolve in water to produce bases.to produce bases.

CaO(s) + HCaO(s) + H22O(l) O(l)

Ca(OH)Ca(OH)22(aq)(aq)

Lewis Acids and BasesLewis Acids and Bases Most general definition:Most general definition: Acids are electron pair acceptors.Acids are electron pair acceptors. Bases are electron pair donors.Bases are electron pair donors.

B FF

F

:NH

H

H

Lewis Acids and BasesLewis Acids and Bases Boron triflouride wants more Boron triflouride wants more electrons.electrons.

B FF

F

:NH

H

H

Lewis Acids and BasesLewis Acids and Bases Boron triflouride wants more Boron triflouride wants more electrons.electrons.

BFBF33 is Lewis acid NH is Lewis acid NH33 is a is a

Lewis base. Lewis base.

BF

F

F

N

H

H

H

Lewis Acids and BasesLewis Acids and Bases

Al+3 ( )HHO

Al( )6

H

HO

+ 6

+3

Comparing the AcidsComparing the Acids ModelModel Acid AcidBaseBase

ArrheniusArrhenius HH++ producer producer OHOH-- Producer Producer B-LowryB-Lowry HH++ donor donor H H+ + AcceptorAcceptor LewisLewis ee-- pair acceptor pair acceptor ee-- pair pair donordonor