Biomedical Science Health and Society, Malmö University Sergey Shleev Chemistry “Acids, bases,...
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Transcript of Biomedical Science Health and Society, Malmö University Sergey Shleev Chemistry “Acids, bases,...
Biomedical Science
Health and Society, Malmö University
Sergey Shleev
Chemistry
“Acids, bases, pH, pK, pI”
Antoine Lavoisier (1743 - 1794)
Pioneer of analytical chemistryand chemical nomenclature
”One of the first defenition of acids” 1780
Nitrogen (N2) – kväve – (Greek: “no life”)
Hydrogen (H2) – väte – gas which is “water-former“ (Greek)
Oxygen (O2) – syrgas – gas which is "acid-former“(Greek: “becoming sharp”) H2SO4HClO4
SimpleComplex
Nonmetals[S, P]
Metals[K, Na, Ca]Oxides
acidic[SO2, SO3, P2O5,]
basic[K2O, Na2O, CaO]
Acids
Bases[KOH, NaOH, Ca(OH)2]
Salts[KCl,,NaSO4]
oxoacids[HPO3, H4P2O7, H3PO4
H2SO3, H2SO4]nonoxo[HCl, HF,HCN, H2S]
Hydride
Metals[KH, NaH,
CaH2]
Nonmetals[PH3, SiH4]
Inorganic substances
Svante August Arrhenius (1859 - 1927)
”Theory of electrolytic dissociation” – 1887
Nobel Price in Chemistry – 1903
Arrhenius theory that describes aqueous solutions in terms of acids (which dissociate to give hydrogen ions)
and bases (which dissociate to give hydroxyl ions);the product of an acid and a base is a salt and water
This theory is still involved in our modern understanding ofelectrolytes, electrical conductivity of solutions, etc
HA H+ + A- AOH A+ + OH-
HCl NH4OH
White
smoke
HCl + NH3 = NH4Cl
?
HCl + NH4OH = NH4Cl + H2O
??Al(OH)3 or H3AlO3
???[Al(H2O)6]3+
electrical conductivity of melts?
Johannes Nicolaus Brønsted (1879–1947)
Thomas Martin Lowry (1874–1936)
1923- formulation of the protonic definition ofacids and bases, both in solution and in gas phase
BH+ + OH- B + H2O
Gilbert Newton Lewis (1875–1946)
1923 - the electron-pair theory of acid-base reactions
the donation of electron pairs from bases and the acceptance by acids, rather than protons or other bonded substances
The theory spans both aqueous and non-aqueous reactions
Inorganic substances
SimpleComplex
nonmetals[S, P]
metals[K, Na, Ca]Oxides
acidic[SO2, SO3, P2O5,]
basic[K2O, Na2O, CaO]
Basic hydroxides
[KOH, NaOH]
Salts[NaSO4]
Acidic hydroxides
[HPO3, H4P2O7, H3PO4
H2SO3, H2SO4]
Hydride
metals[KH, NaH]
Amphoteric[Al]
Amphoteric[Al2O3]
Amphoteric
hydroxides
[Al(OH)3]
Nonmetals[PH3, SiH4]
Halides
Metalic[KCl, NaF]
Nonmetalic[HCl, HF]
Chelates[K3Fe(CN)6]
HA H+ + A-
HA+H2O H3O+ + A-
Arrhenius
Brønsted-Lowry
BH+ + OH- B + H2O
acid + base conjugate base + conjugate acid
Strong acid
Week acid
Dissociation of an acid can be written in several possible ways:
HA+ <=> A + H+
HA <=> A- + H+
HA- <=> A2- + H+
Note that in some cases the conjugate base (A, A-, or A2-) has a negative charge and in other cases it does not,
but in all cases it has one less positive charge than the acid.
For convenience, we will always write such reactions asHA <=>H+ + A-
The equilibrium constant (Ka) for the dissociation of a weak acid (often called the dissociation constant):
][]][[
HAHA
Ka
Mathematics
“Logarithms, exponents,and quadratic equations”
exponents
xay
xey
.........718.2e
y a xobserved variable constant controlled variable
Euler's number
Arrhenius law(equation)
RT
Ea
eAk
k A Ea
R T
activation energy(T independent constant; (kJ mol-1)
frequency or pre-exponential factor
temperatue(K)
gas constant(8.3155 J K-1 mol-1)
rate constant ofchemical reaction
Logarithms
Natural logarithm ln(x) – the inverse function to exponential (ex)
log(x) – the inverse function to 10x
So…
xey xy ln
xy 10 xy log
pKa «acid dissociation constant»
pKb «base dissociation constant»
][]][[
HAHA
Ka
alogKpKa
][]][[
BOHBH
Kb
KbpKb log
Kw “self-ionization constant of water”
2H2O H3O+ + OH-
143 10]][[ OHOHKw
LmolOHH /10][][ 7
hydronium hydroxide
ba KKKw
pH «power of hydrogen» HapH log
HHCfa
HCpH log
pOH
OHOHCfa
OHapOH log
OHCpOH log
quadratic equations
x
Henderson–Hasselbalch equation
][
][log
HA
ApKpH a
][
][log
B
BHpKpOH b
)()(
pHdnd
BC
))(
][][
(3.2)(
)(2
HKKC
HHK
pHdnd
a
aAw
Buffer capacity
pI «isoelectic point» the pH at which a particular molecule or surface carries no net electrical charge
For glycine, an amino acid with only one amine and one carboxyl group
221 pKpK
pI
6.06 2.35 9.78
Asp ? 1.99 9.90
Lys ? 2.16 9.06
pI pK1 pK2pKs
3.90
10.54(9.6)
(2.8)
The relative concentrations of the three forms of glycineas a function of pH