Acids, Bases, and pH Acids, Bases, and pH Acids, Bases, and pH Acids, Bases, and pH.
9 - 1Chemistry for Allied Health: Chapter 10 Acids and Bases Acids & Bases Ionization of Water pH...
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9 - 1Chemistry for Allied Health: Chapter 10
Acids and BasesAcids and Bases
Acids & BasesAcids & Bases
Ionization of WaterIonization of Water
pHpH
Acid-Base ReactionsAcid-Base Reactions
Salt SolutionsSalt Solutions
BuffersBuffers
DilutionsDilutions
TitrationsTitrations
9 - 2Chemistry for Allied Health: Chapter 10
Remember ElectrolytesRemember Electrolytes
Na+
NaCl
Na+ Cl-
Cl-
C6H12O6
C6H12O6
C6H12O6
IonicIonic CovalentCovalent
9 - 3Chemistry for Allied Health: Chapter 10
AcidsAcids
H+
HC2H3O2
H+C2H3O2
1-
C2H3O21- H+
H-Cl
H+Cl-
Cl-
WeakWeak StrongStrong
Lots of IonsOnly a few Ions
9 - 4Chemistry for Allied Health: Chapter 10
AcidsAcids
AcidAcid = gives hydrogen ions in water
H+
H-Cl
H+Cl-
Cl-
HCl
H+ + Cl-
hydrogen ionhydrogen ion
9 - 5Chemistry for Allied Health: Chapter 10
AcidsAcids
H-Cl + H-O-H
+ Cl-
hydronium ionhydronium ion
HO
H
H+
HO
H
H+
Cl-
H-ClH-Cl
AcidAcid = gives hydrogen ions in water
9 - 6Chemistry for Allied Health: Chapter 10
CommonCommon AcidsAcidsBattery Acid Stomach Acid
Coca Cola Carbonated Water
Vinegar Citrus fruitsVitamin CGrapesAspirin
H2SO4
HCl
H3PO4
H2CO3
HC2H3O2
H3C6O7H8
HC6O6H7 H2C4O6H4 H2C9O4H8
Sulfuric AcidHydrochloric Acid
Phosphoric Acid
Carbonic AcidAcetic AcidCitric Acid Ascorbic Acid Tartaric AcidAcetyl Salicylic Acid
9 - 7Chemistry for Allied Health: Chapter 10
H2SO4
HCl
H3PO4
H2CO3
HC2H3O2
H3C6O7H8
HC6O6H7 H2C4O6H4 H2C9O4H8
CommonCommon AcidsAcidsBattery Acid Stomach Acid
Coca Cola Carbonated Water
Vinegar Citrus fruitsVitamin CGrapesAspirin
StrongStrong•100% ionization100% ionization•Strong electrolyteStrong electrolyte
WeakWeak•Partial ionizationPartial ionization•Weak electrolyteWeak electrolyte
•Taste sourTaste sour
9 - 8Chemistry for Allied Health: Chapter 10
AcidsAcidsH-Cl + H-O-H + Cl-
HO
H
H+
HO
H
H+
Cl-
H-ClH-Cl
H+
HC2H3O2
C2H3O21-
HC2H3O2
H-C2H3O2 + H-O-HH
OH
H+ + C2H3O2
-
9 - 9Chemistry for Allied Health: Chapter 10
BaseBase = gives hydroxide ions in water.(Arrhenius definition)
= takes hydrogen ions in water.(Bronsted-Lowry definition)
BasesBases
NaOH
Na+ + OH-OH-
OH-
Na+
Na+
NaOH
9 - 10Chemistry for Allied Health: Chapter 10
Common BasesCommon BasesLye, Drano Potash
Cleaners
Milk of MagnesiaBaking soda Tums /Rolaids Limestone, shellsSoaps Detergents
NaOH KOH
NH3 or NH4OH
Mg(OH)2
NaHCO3
CaCO3
NaC16O2H31 NaC12O4H25S
Sodium HydroxidePotassium Hydroxide
Ammonia
Magnesium HydroxideSodium BicarbonateCalcium Carbonate
Sodium Palmitate Sodium Lauryl
Sulfate
9 - 11Chemistry for Allied Health: Chapter 10
Common BasesCommon BasesLye, Drano Potash
Cleaners
Milk of MagnesiaBaking soda Tums /Rolaids Limestone, shellsSoaps Detergents
NaOH KOH
NH3 or NH4OH
Mg(OH)2
NaHCO3
CaCO3
NaC16O2H31 NaC12O4H25S
StrongStrong•100% ionization100% ionization•Strong electrolyteStrong electrolyte
WeakWeak•Partial ionizationPartial ionization•Weak electrolyteWeak electrolyte
•Taste bitterTaste bitter•Feel SlipperyFeel Slippery
9 - 12Chemistry for Allied Health: Chapter 10
HClO4
H2SO4
HIHBrHCl
HNO3
Perchloric AcidSulfuric AcidHydroIodic AcidHydrobromic AcidHydrochloric AcidNitric Acid
Strong AcidsStrong Acids
LiOHOHNaOH KOH Ca(OHOH)2
Lithium HydroxideSodium HydroxidePotassium HydroxideCalcium Hydroxide
Strong BasesStrong Bases
9 - 13Chemistry for Allied Health: Chapter 10
HNO3 + H2O H3O+ + NO3
-
Water is AmphotericWater is Amphoteric
AcidAciddonates a proton
BaseBasetakes
a proton
NHNH33 + H2O NH4+ + OH-
NHNH33
AcidAciddonates a proton
BaseBasetakes
a proton
HHNONO33
AcidAciddonates a proton
BaseBasetakes
a proton
AcidAcid BaseBase
9 - 14Chemistry for Allied Health: Chapter 10
NH3 + H2O NH4+ + OH- NH3 + H2O NH4+ + OH-
9 - 15Chemistry for Allied Health: Chapter 10
HH22COCO33 + H + H22O HO H33OO++ + + HCOHCO33--
Conjugate Acid - Base PairsConjugate Acid - Base Pairs
conjugate pairconjugate pair
AcidAcid BaseBase AcidAcid BaseBaseconjugate pairconjugate pair
9 - 16Chemistry for Allied Health: Chapter 10
HH22OO
Conjugate Acid - Base PairsConjugate Acid - Base Pairs
Acid - Acid - BaseBaseHH22COCO33 HHCOCO33
1-1- COCO332-2-
HH33OO++ HOHO1-1-
HH33POPO44HH22POPO44
1-1- POPO443-3-HHPOPO44
2-2-
Acid - Acid - BaseBaseAcid - Acid - BaseBase
Acid - Acid - BaseBaseAcid - Acid - BaseBaseAcid - Acid - BaseBaseAcid - Acid - BaseBase
Acid - Acid - BaseBaseAcid - Acid - BaseBaseAcid - Acid - BaseBaseAcid - Acid - BaseBase Acid - Acid - BaseBase Acid - Acid - BaseBase
9 - 17Chemistry for Allied Health: Chapter 10
HH22COCO33 + H + H22O HO H33OO++ + + HCOHCO33--
AcidAcid BaseBase AcidAcid BaseBase
Dissociation ConstantsDissociation Constants
KKeq = = [ [ HH33OO++ ] [ ] [HCOHCO33--]
[[HH22COCO33 ] [] [HH22O]O]
[[HH22O]O][[HH22O]O]
KKaa== [ [ HH33OO++ ] [ ] [HCOHCO33
--] [[HH22COCO33 ]]
Acid Dissociation ConstantAcid Dissociation Constant
9 - 18Chemistry for Allied Health: Chapter 10
HH22COCO33 + H + H22O HO H33OO++ + + HCOHCO33--
ACIDACID BASEBASE conj acidconj acid conj baseconj base
Dissociation ConstantsDissociation Constants
KKaKKa == [ [ HH33OO++ ] [ ] [HCOHCO33
--] [[HH22COCO33 ]]
ACID Dissociation ConstantACID Dissociation ConstantACID Dissociation ConstantACID Dissociation Constant
Small KSmall Ka a (<1) Weak Acid (<1) Weak Acid [ reactant]>[product][ reactant]>[product]Small KSmall Ka a (<1) Weak Acid (<1) Weak Acid [ reactant]>[product][ reactant]>[product]
= 4.5 x 10= 4.5 x 10-7-7= 4.5 x 10= 4.5 x 10-7-7
Large KLarge Ka a (>1) Strong Acid (>1) Strong Acid [product]>[reactant][product]>[reactant]Large KLarge Ka a (>1) Strong Acid (>1) Strong Acid [product]>[reactant][product]>[reactant]
9 - 19Chemistry for Allied Health: Chapter 10
HH22O O + H + H22O O HOHO-- + + HH33OO++
Ionization of WaterIonization of Water
conjugate pairconjugate pair
ACIDACID BASEBASE conj acidconj acidconj baseconj base
conjugate pairconjugate pair
9 - 20Chemistry for Allied Health: Chapter 10
HH22O O + H + H22O O HOHO-- + + HH33OO++
Ion product constant of WaterIon product constant of Water
ACIDACID BASEBASE conj acidconj acidconj baseconj base
0.000,000,1M0.000,000,1M= 1 x 10= 1 x 10-7-7MM
0.000,000,1M0.000,000,1M= 1 x 10= 1 x 10-7-7MM
Neutral: if [HNeutral: if [H33OO++] = [OH] = [OH--] ]
Acidic: if [HAcidic: if [H33OO++] > [OH] > [OH--] ]
Basic: if [HBasic: if [H33OO++] < [OH] < [OH--] ]
9 - 21Chemistry for Allied Health: Chapter 10
HH22O O + H + H22O O HOHO-- + + HH33OO++
Ion product constant of WaterIon product constant of Water
ACIDACID BASEBASE conj acidconj acidconj baseconj base
0.000,000,1M0.000,000,1M= 1 x 10= 1 x 10-7-7MM
0.000,000,1M0.000,000,1M= 1 x 10= 1 x 10-7-7MM
KKww = [H = [H33OO++] [OH] [OH--] = ] = 1 x 101 x 10-14-14KKww = [H = [H33OO++] [OH] [OH--] = ] = 1 x 101 x 10-14-14
[H[H33OO++] [OH] [OH--] = ] = (1 x 10(1 x 10-7-7))(1 x 10(1 x 10-7-7)) = =1 x 101 x 10-14-14[H[H33OO++] [OH] [OH--] = ] = (1 x 10(1 x 10-7-7))(1 x 10(1 x 10-7-7)) = =1 x 101 x 10-14-14
9 - 22Chemistry for Allied Health: Chapter 10
pH pH pH pH
= 1 x 10 -pH pH = pH = - log [H+]
HCl
HC2H3O2
H2O
NaOH
0.000,000,1 M = 1 x 10 -7 M
[H+]
0.000,1 M = 1 x 10 -4 M
0.000,000,000,001 M = 1 x 10 -12 M
100 M = 1 x 10 2 M
77
44
1212
-2-2
990.000,000,001 M 0.000,000,001 M
= 1 x 10 = 1 x 10 -9-9 M MNHNH33
NeutralNeutral
AcidicAcidic
BasicBasic
9 - 23Chemistry for Allied Health: Chapter 10
pHpH pHpH = 1 x 10 -pH pH = pH = - log [H+]
HCl
HC2H3O2
H2O
NaOH
0.000,000,1 M = 1 x 10 -7 M
[H+]
0.000,1 M = 1 x 10 -4 M
0.000,000,000,001 M = 1 x 10 -12 M
100 M = 1 x 10 2 M
77
44
1212
-2-2
990.000,000,001 M 0.000,000,001 M
= 1 x 10 = 1 x 10 -9-9 M MNHNH33
NeutralNeutral
AcidicAcidic
BasicBasic
Citric AcidCitric Acid 0.000,76 M 0.000,76 M = 7.6 x 10 = 7.6 x 10 -4-4 M M
9 - 24Chemistry for Allied Health: Chapter 10
pH pH pH pH
= 1 x 10 -pH pH = pH = - log [H+]pH = pH = - log [H+]
HC2H3O2
[H+]
0.000,1 M = 1 x 10 -4 M 44
3 - 43 - 43 - 43 - 4
Citric AcidCitric Acid
0.001 M = 1 x 10 -3 M
0.000,76 M 0.000,76 M = 7.6 x 10 = 7.6 x 10 -4-4 M M
33
pH = pH = - log (7.6 x 10 -4)pH = pH = - log (7.6 x 10 -4)
= 3.1= 3.1= 3.1= 3.1
9 - 25Chemistry for Allied Health: Chapter 10
pH pH pH pH
[H[H++]] = 1 x 10 = 1 x 10 -pH-pH[H[H++]] = 1 x 10 = 1 x 10 -pH-pH pH = pH = - log [H+]pH = pH = - log [H+]
0.000,000,04 M = 4.0 x 10 4.0 x 10 -8-8 M M
9.39.3
8.58.58.58.5Baking Baking SodaSoda
= 1 x 10 -8.5 M= 3.2 x 10 3.2 x 10 -9-9 M M
pH = pH = - log (4.0 x 10 -8)pH = pH = - log (4.0 x 10 -8)
= 7.4= 7.4= 7.4= 7.4
CleanerCleaner = 1 x 10 -9.4 M= 5.0 x 10 5.0 x 10 -10-10 M M
BloodBlood
9 - 26Chemistry for Allied Health: Chapter 10
pH of somepH of somecommon materialscommon materials
Substance pH
1 M HCl1 M HCl 0.0
Lemon juiceLemon juice 2.3
CoffeeCoffee 5.0
Pure WaterPure Water 7.0
BloodBlood 7.35-7.45
MilkMilk of Magnesia 10.5
1M NaOH1M NaOH 14.0
9 - 28Chemistry for Allied Health: Chapter 10
pH meter:pH meter:
pH paperpH paper::
LitmusLitmus paperpaper::
Pigments:Pigments:Anthocyanins:Anthocyanins:
red cabbagered cabbage, , cranberriescranberries, , rosesroses……Phenolphthalein:Phenolphthalein:Turmeric:Turmeric:
9 - 29Chemistry for Allied Health: Chapter 10
Indicator examplesIndicator examplesAcid-base indicators undergo a color change
at a known pH.
bromthymol blue
phenolphthalein methyl red
9 - 30Chemistry for Allied Health: Chapter 10
AcidAcid--BaseBase Reactions Reactions
HClHCl + + NaOHNaOH
OHOH--
ClCl--
NaNa++
HH++
NaNaClCl + + HHOHOH
AcidAcid BaseBase SaltSalt WaterWater
Neutralization:Neutralization:Strong AcidStrong Acid
++Strong BaseStrong Base
9 - 31Chemistry for Allied Health: Chapter 10
AcidAcid--BaseBase Reactions Reactions
HH22SOSO44 + + KOHKOH
OHOH--
SOSO44-2-2
KK++
HH++
KK22SOSO44 + + HHOHOHAcidAcid BaseBase SaltSalt WaterWater
2222
9 - 32Chemistry for Allied Health: Chapter 10
AcidAcid--BaseBase Reactions Reactions
HCHC22HH33OO22 + + NaHCONaHCO33
HCOHCO331-1-
CC22HH33OO221-1-
NaNa++
HH++
NaNaCC22HH33OO22 + + HH22COCO33
AcidAcid BaseBase
SaltSalt
HH22OO + + COCO2(g)2(g)
9 - 33Chemistry for Allied Health: Chapter 10
AcidAcid--BaseBase Reactions Reactions
Acid Rain on MarbleAcid Rain on Marble
Cream of Tartar & Baking SodaCream of Tartar & Baking Soda
Lemon on FishLemon on Fish
9 - 34Chemistry for Allied Health: Chapter 10
BuffersBuffers
HCHC22HH33OO22 NaCNaC22HH33OO22
9 - 35Chemistry for Allied Health: Chapter 10
Bronsted-Lowry theoryBronsted-Lowry theory
AcidAcid = a Proton donor donates a proton, H+, to solvent
Example: HClHCl
HCl + H2O H3O+ + Cl-
hydronium ion
9 - 36Chemistry for Allied Health: Chapter 10
Example: HNO3
HNO3 + H2O HH33OO++ + NO3-
HNO3 is the acid: it donates the proton.
Bronsted-Lowry theoryBronsted-Lowry theory
9 - 37Chemistry for Allied Health: Chapter 10
Base Base == a proton acceptor accepts a Proton, H+, from solvent
NHNH33 + H2O NH4+ + OH-
Accepted H+
Bronsted-Lowry theoryBronsted-Lowry theory
NH3 is the Base: it takes the proton.
9 - 38Chemistry for Allied Health: Chapter 10
Hydroxide ions Hydroxide ions (OH-) form when water donates the proton.
NH3 + H2O NH4+ + OH-
Bronsted-Lowry theoryBronsted-Lowry theory
9 - 39Chemistry for Allied Health: Chapter 10
In reverse rxn:
gives the HH++ back to HCOHCO33--
In forward rxn:H2CO3 gives the HH++ to H-O-HH-O-H..
HH22COCO33 + + HH22O O HH33OO++ + + HCOHCO33--
ACID ACID 11 BASE BASE 22 ACID ACID 22 BASE BASE 11
Conjugate Acid - Base PairsConjugate Acid - Base Pairs
HH-O-H +
9 - 43Chemistry for Allied Health: Chapter 10
Polyprotic AcidsPolyprotic Acids
Polyprotic acidsPolyprotic acids = Acids that donate >1 H+:
H2SO4, H2CO3, and H3PO4.
9 - 44Chemistry for Allied Health: Chapter 10
HHPOPO442-2- + H + H22O POO PO44
3-3- + + HH33OO++
HH22POPO44-- + H + H22O O HHPOPO44
2-2- + + HH33OO++
H+’s donate 1 at a time. Example: Phosphoric acid
HH33POPO44 + H + H22O O HH22POPO44-- + + HH33OO++
9 - 48Chemistry for Allied Health: Chapter 10
THE COMMON THE COMMON -IC-IC ACIDS ACIDS
H2SO4 SULFURIC ACID
HNO3 NITRIC ACID
H2CO3 CARBONIC ACID
H3PO4 PHOSPHORIC ACID
HClO3 CHLORIC ACID
9 - 50Chemistry for Allied Health: Chapter 10
EXAMPLE:
HH22SOSO44 (S= +6) Sulfuric acid
HH22SOSO33 (S= +4) Sulfurous acid
HH22SOSO22 (S= +2) hyposulfurous acid
9 - 52Chemistry for Allied Health: Chapter 10
The highest of these four acids is prefixed with a per- (from hyper meaning above).
HClOHClO44 perperchlorchloricic acid acid
HClOHClO33 chloricchloric acid acid
HClOHClO22 chlorouschlorous acid acidHClOHClO hypohypochlorchlorous ous acidacid
9 - 57Chemistry for Allied Health: Chapter 10
Acid SaltsAcid Salts
When an acid has more than one H+ to donate (polyprotic acids), it may form anions with hydrogens still attached.Acid Anions
H2SO4 HSO4- SO4
2-
H2CO3 HCO3- CO3
2-
H3PO4 H2PO4- HPO4
2- PO43-
The anions are still capable of donating these protons, and the salts they form are called acid salts.
9 - 58Chemistry for Allied Health: Chapter 10
These anions are named by indicating the indicating the # of hydrogens left.# of hydrogens left.
HH22PO4- dihydrogendihydrogen phosphate ion
HHPO42- monohydrogenmonohydrogen phosphate
ionHHSO4
- hydrogenhydrogen sulfate
HHSO3- hydrogenhydrogen sulfite
HHCO3- hydrogenhydrogen carbonate
9 - 59Chemistry for Allied Health: Chapter 10
The prefix bi- bi- indicates 1 hydrogen is left from a dihydrogen acid.
HCO3- bicarbonatebicarbonate
HSO3- bisulfitebisulfite
9 - 60Chemistry for Allied Health: Chapter 10
WATERWATER
Water is important for many reasons:
Universal solventUniversal solvent Biological solventBiological solvent Small sizeSmall size Density of water is greater than iceDensity of water is greater than ice Very polarVery polar Hydrogen BondingHydrogen Bonding
9 - 61Chemistry for Allied Health: Chapter 10
Amphoteric SubstancesAmphoteric Substances
Water is amphotericamphoteric : Can act as an acidacid or a or a basebase,
HC2H3O2(aq) + HH22OO(l) HH33OO++ + CC22HH33OO22--((aq)
acid base acid base
HH22OO(l) + NHNH33(aq) NHNH44++
((aq) + OHOH--((aq)
acid base acid baseHERE WATER ACTS AS BOTH AN ACID AND A BASE
9 - 62Chemistry for Allied Health: Chapter 10
The Self-ionization of WaterThe Self-ionization of Water
H2O + H2O H3O+ + OH-
Acid BaseBase
9 - 63Chemistry for Allied Health: Chapter 10
At 25oC, this ionization involves only 1 out of every 550,000,000550,000,000 H2O molecules.
HH22OO(l)(l) + H + H22OO(l)(l) HH33OO++((aq)aq) + + OHOH--
((aqaq) (10-7M) (10-7M)
In 1L H2O, the number of H3O+ and OH- ions formed is 1 x 10-7 moles each.
[ H[ H33OO+ + ]] = 1 x 101 x 10-7 -7 moles/litermoles/liter[ OH[ OH- - ]] = 1 x 10 x 10-7-7 moles/liter moles/liter
9 - 64Chemistry for Allied Health: Chapter 10
In all aqueous solutions, the ion production product for H2O must always be equal to 1.0 x 10equal to 1.0 x 10-14-14
Kw = [ H[ H33OO+ + ]] [ OH[ OH- - ]]
Kw = 1.0 x 101.0 x 10-14-14 at 25 at 25ooCC
Note:Note: [H[H22O]O] is constant and is already included in Kw. (see pg. 260 in text)
9 - 65Chemistry for Allied Health: Chapter 10
If some acid is added to HIf some acid is added to H22OO, causing the [H+] to increase to 0.001 M (1 x 10-3 M), the the [OH[OH--] will decrease to keep Kw = 1 x 10] will decrease to keep Kw = 1 x 10-14-14..
Solving for the new OH- concentration:[H+] x [OH-] = 1 x 101 x 10-14-14
(1 x 10-3) x [OH-] = 1 x 10-14
9 - 66Chemistry for Allied Health: Chapter 10
[OH-][OH-] = = 1 x 101 x 10-11-11 or 0.00000000001M
[OH-][OH-] = 1 x 10-14
1 x 10-3
9 - 67Chemistry for Allied Health: Chapter 10
ProblemProblem: What is the [OH[OH--]] in a solution where [H[H++] is 0.035 M] is 0.035 M ?
Solution:1. Express [H+] in scientific notation.
[H[H++] = 3.5 x 10] = 3.5 x 10-2-2
2. Find [OH-] from Kw.[OH-] = Kw
[H+]
9 - 68Chemistry for Allied Health: Chapter 10
[OH[OH--]] = 1 x 101 x 10-14-14
3.5 x 103.5 x 10-2-2
Answer: [OH[OH--]] = = 2.86 x 102.86 x 10-13-13
9 - 69Chemistry for Allied Health: Chapter 10
pH and pOHpH and pOH
We need to measure and use acids and bases over a very large concentration range.
pH and pOH are systems to keep track of these very large ranges.
pH = -log[HpH = -log[H33OO++]]pOH = -log[OHpOH = -log[OH--]]
pHpH + pOHpOH = 1414
9 - 78Chemistry for Allied Health: Chapter 10
WEDNESDAYWEDNESDAYJANUARY 26, 2000JANUARY 26, 2000
http://terra.chemek.cc.or.us/faculty/mcnm/winter/webpage.htm
9 - 79Chemistry for Allied Health: Chapter 10
The pH ScaleThe pH Scale
Using scientific notation to express [H+] or [OH-] (ex. 3.1 x 103.1 x 10-6-6, 1.0 x 101.0 x 10-7-7, etc.), although simpler than decimal notation, can be cumbersome.
The pH method simplifiespH method simplifies expression of [H+].
9 - 80Chemistry for Allied Health: Chapter 10
pH = -log [HpH = -log [H++] or [H[H++] = 1 x 10] = 1 x 10-pH-pH
pH is the negative of the power which the number 10 must be raise to express the [H+].
9 - 81Chemistry for Allied Health: Chapter 10
Most naturally occurring acids have [H+] much less than 1M.
Orange juiceOrange juice, for example, has [H+] = 2.0 x 10-4 or 0.00020.0002.
Log 2.0 x 10-4 = -3.7
(i.e. 10-3.7 = 2.0 x 10- 4)
9 - 82Chemistry for Allied Health: Chapter 10
Although expressing the concentration in the form of an exponent simplifies it somewhat, the fact that it is almost always a negative number can be a problem.
This is why pHpH is defined as the negativenegative of this exponentexponent. It simply gives us a positivepositive number to work with.
9 - 83Chemistry for Allied Health: Chapter 10
Logarithms are exponents!! Logarithms are exponents!! Log 100 refers to the exponent that the number 10 must be raised to in order to obtain the number 100.
Log 100 = 2 (i.e. 10 2 = 100)Every number has a logarithm.Log 50 = 1.69 (i.e. 10 1.69 = 50)Log 0.0045 = -2.347 (i.e. 10-2.347 = 0.0045)
9 - 84Chemistry for Allied Health: Chapter 10
9 - 85Chemistry for Allied Health: Chapter 10
9 - 86Chemistry for Allied Health: Chapter 10
pOH examplespOH examples
Determine the following: pOH = -log[OH-]
or 14 - pH1. pOH of 1.7x10-4 M NaOH pOH = 3.8 pH = 10.2
2. pOH of 5.2x10-12 M H+
pH = 11.2 pOH = 2.8
3. [OH-] , if the pH is 4.5 pOH = 9.5 [OH-] = 3.2x10-10 M
9 - 87Chemistry for Allied Health: Chapter 10
pH scalepH scale
A log based scale used to keep track of the large change important to acids and bases.
14 7 0
10-14 M 10-7 M 1 MVery Neutral VeryBasic Acidic
When you add an acid, the pH gets smaller.
When you add a base, the pH gets larger.
9 - 88Chemistry for Allied Health: Chapter 10
pH of somepH of somecommon materialscommon materials
Substance pH
1 M HCl1 M HCl 0.0
Lemon juiceLemon juice 2.3
CoffeeCoffee 5.0
Pure WaterPure Water 7.0
BloodBlood 7.35-7.45
MilkMilk of Magnesia 10.5
1M NaOH1M NaOH 14.0
9 - 89Chemistry for Allied Health: Chapter 10
HCl + NaOH NaCl + H2O
NeutralizationNeutralization
The reaction of an acid with a base to produce a salt and water.
We do this when we use antacids.
Neutralization can be used to Determine the amount of acid or base in a sample.
titrationstitrations
9 - 90Chemistry for Allied Health: Chapter 10
Analytical methods based on measurment of volumemeasurment of volume.
• If the concentration of an acid is concentration of an acid is knownknown, the concentration of the base concentration of the base can be found.can be found.
• If we know the concentration of the base, then we can determine the amount of acid.
• All that is needed is some calibrated calibrated glasswareglassware and either an indicatorindicator or pH pH meter.meter.
TITRATIONSTITRATIONS
9 - 91Chemistry for Allied Health: Chapter 10
BuretBuret - volumetric glasware used for titrations.
It allows you to add a known amount of your titrant to the solution you are testing.
If a pH meter is used, the equivalence point can be measured.
An indicator will give you the endpoint.
9 - 92Chemistry for Allied Health: Chapter 10
Indicator examplesIndicator examples
Acid-base indicators are weak acids that undergo a color change at a known pH.
bromthymol blue
phenolphthalein methyl red
9 - 93Chemistry for Allied Health: Chapter 10
HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq)
All of these reactions occur in solution where the acid and base are separated into their ions.
Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) H2O(l) + Na+(aq) + Cl-(aq)
The salt is usually in the form of its dissolved ions.
9 - 94Chemistry for Allied Health: Chapter 10
It is the formation of H2O that actually allows the reaction to proceed.
HH++((aq) + OHOH--((aq) HHOHOH(l)(l)
This is the “net ionic”“net ionic” equation for almost all acid/base neutralizationacid/base neutralization reactions.
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H2CO3 + 2NaOH Na2CO3 + 2H20
HCL + NaOH NaCl + H20
Salts Salts are formed from neutralization neutralization reactionsreactions.
Acid Base Salt Water
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Salts are named after the metalmetal and the acid acid anionanion.
Na2CO3 sodium carbonate
NaClO sodium hypochloriteKH2PO4 potassium dihydrogen phosphate
NaHCO3 sodium bicarbonate
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Common laboratoryCommon laboratoryacids and basesacids and bases
Molarity
AcidsAcids Formula (undiluted)nitric HNO3 16
hydrochloric HCl 12sulfuric H2SO4 18acetic HC2H3O2 18
BasesBasesammonium hydroxide NH4OH 15sodium hydroxide NaOH solid
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Properties of acidsProperties of acids
• Sour taste.
• Produce H3O+ when dissolved in water.
• Undergo double replacement reactions with solid oxides, hydroxides, carbonates and bicarbonates.
HCl + NaOH NaCl + H2O
2 HCl + CaCO3 CaCl2 + CO2 + H2O
HCl + NaHCO3 NaCl + CO2 + H2O
2 HCl + CuO CuCl2 + H2O
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Properties of acidsProperties of acids
Another property is the ability to react with metals, producing hydrogen gas.
Zn + 2 HCl ZnCl2 + HH22(g)(g)
Some metals react better with acids than others. We can show the reactivity using an
activity seriesactivity series
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Activity series of metalsActivity series of metals
potassiumsodium
potassiumsodium
calciumcalcium
magnesiumaluminum
zincchromium
magnesiumaluminum
zincchromium
ironnickel
tinlead
ironnickel
tinlead
coppersilver
platinumgold
coppersilver
platinumgold
incr
easi
ng
rea
ctiv
ity
Reacts violently with cold water
Reacts slowly with cold water
Reacts very slowly with steambut quite reactive in acid
Reacts moderately with highlevels of acid
Unreactive in acid
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Activity series of metals -Activity series of metals -various metals in HClvarious metals in HCl
Iron Zinc Magnesium
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Properties of basesProperties of bases
• Solutions have a slippery or soapy feel.• Will react with acids to produce a salt.
Neutralization reactionNeutralization reaction
NaOH + HCl NaCl + H2O
Neutralization of fatty acids in the skin produce soap. This is why bases feel slippery.
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Acid and Base StrengthAcid and Base Strength
Strong acidsStrong acids dissociate completely in water HCl, HBr, HI, HClOHCl, HBr, HI, HClO33, HNO, HNO33, , HClOHClO44, H, H22SOSO44..
Weak acids Weak acids partially dissociate in water. most acids are weak.
Strong basesStrong bases dissociate completely in water NaOH, LiOH, KOH
strong bases are metal hydroxides.
Weak basesWeak bases partially dissociate in water.
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DissociationDissociation
Strong acids and basesStrong acids and bases• considered to dissociate completely.
HCl(aq) + H2O(l) H3O+ (aq) + Cl-
(aq)
NaOH(aq) + H2O(l) Na+(aq) + OH-
(aq)
Weak acids and basesWeak acids and bases• do not dissociate completely.
HC2H3O2 (aq) + H2O(l) H3O+(aq) +C2H3O2
-(aq)
NH3 (aq) + H2O(l) NH4+ (aq)+ OH-
(aq)
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Acid dissociation constant, KAcid dissociation constant, Kaa
The strength of a weak acid can be expressed as an equilibrium.
HA (aq) + H2O(l) H3O+(aq) + A-
(aq)
The strength of a weak acid is related to its equilibrium constant, Ka.
Ka = [A-][H3O+] [HA]
We omit water.It’s alreadyincluded in
the constant.
We omit water.It’s alreadyincluded in
the constant.
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Dissociation of bases,Dissociation of bases,KKbb
The strength of a weak base can also be expressed as an equilibrium.
B (aq) + H2O(l) BHBH++((aq) +OHOH-
(aq)
The strength of a weak base is related to its equilibrium constant, Kb.
Kb = [OH[OH--][BH][BH++]] [B]
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KKaa and K and Kbb values values
For weak acids and bases
Ka and Kb always have values that are smaller than one.
• Acids with a larger Ka are stronger than ones with a smaller Ka.
• Bases with a larger Kb are stronger than ones with a smaller Kb.
Most acids and bases are considered weak.
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The strengthstrength of an acid is predicated on its ability to dissociate and release Hability to dissociate and release H++,, not on the number of H+ it has available.
Example:Example: Hydrochloric acid (HCl) with only one hydrogen per molecule is a very strong acid whereas Boric acid (H3BO3) with 3X the number of hydrogen’s per molecule is a very weak acid.
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*Acids are a lot like peopleAcids are a lot like people: it’s not what you’ve got but what you do with it that really counts.
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Some Representative Acids
NAME FORMULA CLASSI-FICATION
H30+ FROM 1,000,000
MOLECULES
IN 0.01M
Sulfuric H2SO4 Strong 1,220,000
Nitric HNO3 Strong 920,000
Hydrochloric HCl Strong 920,000
Phosphoric H3PO4 Moderate 270,000
Lactic Acid CH3CHOHCO2H Weak 87,000
Acetic Acid CH3COOH Weak 13,000
Boric Acid H3BO3 Weak Less Than 1
Hydrocyanic Acid
HCN Weak Less Than 1
Less Than 1
Less Than 1
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*No matter how dilute a strong acid may be, it is still a strong acid.
0.001 M HNO3 is a strong acid solution even though dilute.
18 M H2CO3 is a weak acid solution even though concentrated.
DON’T CONFUSE CONCENTRATION WITH DON’T CONFUSE CONCENTRATION WITH STRENGTH !!STRENGTH !!
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HYDROLYSIS REACTIONSHYDROLYSIS REACTIONS
The conjugate base of a weak acid is one that has a strong attraction for H+. If a conjugate base of a weak acid is put into H2O, it will try to reform the weak acid by taking a H+ from H2O.
COCO332-2- + H2O HCO3
- + OHOH--
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HYDROLYSIS REACTIONSHYDROLYSIS REACTIONS
The conjugate base of a weak acid is one that has a strong attraction for H+. If a conjugate base of a weak acid is put into H2O, it will try to reform the weak acid by taking a H+ from H2O.
COCO332-2- + H2O HCO3
- + OHOH--
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HYDROLYSIS REACTIONSHYDROLYSIS REACTIONS
The conjugate base of a weak acid is one that has a strong attraction for H+. If a conjugate base of a weak acid is put into H2O, it will try to reform the weak acid by taking a H+ from H2O.
COCO332-2- + H2O HCO3
- + OHOH--
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HYDROLYSIS REACTIONSHYDROLYSIS REACTIONS
The conjugate base of a weak acid is one that has a strong attraction for H+. If a conjugate base of a weak acid is put into H2O, it will try to reform the weak acid by taking a H+ from H2O.
COCO332-2- + H2O HCO3
- + OHOH--
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HYDROLYSIS REACTIONSHYDROLYSIS REACTIONS
The conjugate base of a weak acid is one that has a strong attraction for H+. If a conjugate base of a weak acid is put into H2O, it will try to reform the weak acid by taking a H+ from H2O.
COCO332-2- + H2O HCO3
- + OHOH--
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HYDROLYSIS REACTIONSHYDROLYSIS REACTIONS
The conjugate base of a weak acid is one that has a strong attraction for H+. If a conjugate base of a weak acid is put into H2O, it will try to reform the weak acid by taking a H+ from H2O.
COCO332-2- + H2O HCO3
- + OHOH--
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HYDROLYSIS REACTIONSHYDROLYSIS REACTIONS
The conjugate base of a weak acid is one that has a strong attraction for H+. If a conjugate base of a weak acid is put into H2O, it will try to reform the weak acid by taking a H+ from H2O.
COCO332-2- + H2O HCO3
- + OHOH--
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This is why washing soda (Na2CO3) is added to water. The conjugate base reforms the weak acid molecule producing OH- ions and making the water alkaline. Clothes get cleaner in alkaline water.
COCO332-2- + H + H22O HCOO HCO33
-- + + OHOH--
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BuffersBuffers
BUFFERS: Control of pH
Our bodies are acid factories.• STOMACH: produces Hydrochloric acid. • MUSCLES: produce Lactic Acid.• STARCHES and SUGARS: Metabolize to
pyruvic acid• CO2 from RESPIRATION: produces
Carbonic acid in the blood
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• Our bodies must eliminate or neutralize these acids, because excess acidity in the wrong place will kill us.
• A buffer solution is one in which the pH remains relatively constant even if an acid or base is added.
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Chemically, a buffer solution contains a weak acid and one of its’ salts (conjugate base) or a weak base and one of its’ salts (conjugate acid).
HHAA(aq)(aq) + H + H22OO(l)(l) H H33OO++(aq)(aq) + + AA--
((aq)aq)
Add OH- Add H+
shift to right shift to left
Based on LeChatelier’s Principle.
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Ex. H2CO3 + H20 HCO3- + H30+
H2PO4- + H20 HPO4
-2 + H30
NH3 + H20 NH4+ + OH-
H2CO3 / HCO3-
Acid Conjugate base (salt)
H2PO4- / HPO4
-2
Acid Conjugate base (salt)
NH3 / NH4+
Base Conjugate acid (salt)
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How does a buffer work?How does a buffer work?
The salt portion (conjugate baseconjugate base) of the pair combines with H+ to form the acid molecule.
H+ + HCO3- H2CO3
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If the acidity starts to drop too much, the acid portion of the buffer pair dissociates to provide H+.
H2CO3 HH++ + HCO3-
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Example: Physiological salinePhysiological saline is equivalent to a 0.15 M NaCl solution and its pH is 7.0.
Blood plasmaBlood plasma would be like this solution but it has a buffer of HCOHCO33
--/H/H22COCO33 in a 20:1 ratio that pushes the pH to 7.4.
If 1 ml of 10.0 M HCl was added to 1 liter of the unbuffered saline, the pH value of 7.0 would immediately drop to a pH = 2.0. (An increase in acidity of 100,000.)
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In the blood, the H+ is absorbed by HCO3-.
ex. H+ + HCO3- H2CO3
This prevents the pH from drastically changing.
If we had added 1 ml of 10 M HCl to our buffered blood, the pH would go from 7.4 to 7.2.
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This small increase in our blood of the H2CO3 is still a problem. A pH of 7.2 is far too low and would create a condition called acidosis.
But our body is capable of removing this H2C03 from the blood through hyperventilation (increased breathing rate).
HOW????
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1. H2CO3 is formed in the blood
((HCOHCO33-- + H + H++ HH22COCO33))
2. It is carried to the lungs where it will decompose to form CO2.
((HH22COCO33 HH220 + CO0 + CO22))
3. Rapid breathing expels the CO2.
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When the pH of our blood goes up (alkalosis), the other partner in the buffer pair goes to work.
OH- + H2CO3 H20 + HCO3-
Now we are losing H2CO3 and getting too much HCO3
- in the blood. To return the HCO3
-/H2CO3 to normal, our body goes into action.
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1. CO2 is kept in body by slower and shallower breathing (hypoventilation).(Breathing into a paper bag helps.)(Breathing into a paper bag helps.)
2. This allows more H2CO3 to form (CO2 + H20 H2CO3).
3. Kidneys remove excess HCO3- and
release more H+ to blood.
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DiabetesDiabetes MellitusMellitusTransport of glucose (blood sugar) across cell membranes is interrupted.
Sugar thus remains in blood (hyperglycemiahyperglycemia).
Most body tissues must switch over to fat metabolism. (Low carbohydrate diets also Low carbohydrate diets also cause this to happen.)cause this to happen.)
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Acetyl Coenzyme AAcetyl Coenzyme A is formed at excessive rate.
This overloads the Krebs Cycle and body tries to dispose of it by conversion to ketones.ketones. (Often observed as release of acetoneacetone via the breath.)
These ketone bodies are acidic.AcidosisAcidosis soon follows. (pH drops)
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Acidic bloodAcidic blood cannot transport oxygen very well.
Breathing becomes labored and painful.
DiabeticDiabetic comacoma can follow.
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StarvationStarvation:: Body's glycogen stores are depleted rapidly and the body calls on its fat reservesfat reserves. Fat is taken first from around the kidneys and the heart. Then it is removed from other parts of the body, eventually even the bone marrowbone marrow is depleted.
By the same mechanism discussed above, starvationstarvation also leads to ketosis ketosis which rapidly develops into acidosis.acidosis.