1
Henri LeChatelier
French
1884
if a system at equilibrium is disturbed,
reaction shifts to oppose disturbance
(+)
(–)
heat +
+ heat
R P
LeChatelier’s Principle
ΔH + :
ΔH – : A + B C + D + heat
heat + E + F G + H
T
P N2O4(g) 2 NO2(g)
R P
gas moles
heat as P or R
1.
3.
2.
N2(g) + 3 H2(g) 2 NH3(g)
H2(g) + I2(g) 2 HI(g)
no shift from s or ℓ
P(g) vs R(g)
K changes:
Co(H2O)62+ + 4 Cl– CoCl4
2– + 6 H2O
K2Cr2O7 + K2O 2 K2CrO4
Pgas
a. To increase the yield of H2, should the pressure be high or low?
P side (H2) more moles gas (2:1); low P favors more moles
H2 increase
b. To increase the yield of H2, should the temperature be high or low?
T reaction goes in direction to consume heat () (heat as R)
H2 increase
c. What will adding carbon do to the yield of H2?
carbon is a solid no change;
d. What effect will adding Ni metal have on the yield of H2, knowing
that Ni reacts with CO to give Ni(CO)4(ℓ)?
[CO] reaction shifts to make more ()
DHo = +131.3 kJ
C(s) + H2O(g) CO(g) + H2(g) heat +
; H2 increase
2
Chapter 16
Acids and Bases
Base Base
Acid Acid
+ NH3(g)
substance that [OH–] in water
, react with acids
ancient acid:
base: litmus blue , bitter , slippery
, react with bases litmus red , sour , corrosive
Arrhenius acid:
base:
H2O(ℓ) H+(aq) + OH–(aq) connected by:
substance that [H+] (protons) in water
salts
CH3O
N
H
HO
N
quinine
acid:
HCl(g) Cl– + NH4+
+ – +
Brønsted - Lowry
+ –
proton donor (to base)
proton acceptor (acid) base:
Johannes Thomas
Svante
1923
1884
X– M+
Acid – Base Definitions
MX salt
+
–
Gilbert N. acid:
base:
e– pair acceptor (from a base)
e– pair donor (to an acid) 1923
Lewis • • H N H
H
+
– F B F
F
• •
• •
• •
• • • •
• •
• • • •
• •
3
+
Arrhenius:
HCl(aq) H+(aq) + Cl–(aq)
NaOH(aq) OH–(aq) + Na+(aq)
HCl(aq) H3O+(aq) + H2O(ℓ) + Cl–(aq)
acid hydronium ion
NH3(aq) ?
+ –
Brønsted – Lowry:
HCl, NaOH, NH3
base
base – OH–(aq) H2O(ℓ) + H2O(ℓ) + OH–(aq)
acid
NH3(aq) NH4+(aq) + H2O(ℓ) + OH–(aq)
base
+ – acid
+
–
+
hydroxide ion
HA A– + B HB+
H+ transferred both ways:
acid base
base + acid
base acid
acid + base forms
+
General Brønsted-Lowry Acid-Base Reaction
conjugate
base
conjugate
acid
– base
+ acid
conjugate acid-base pairs
+ – +
4
+
HA(aq) + H3O+(aq) + H2O(ℓ) A–(aq)
acid base
B(aq) HB+(aq) + H2O(ℓ) + OH–(aq)
acid base basic
Aqueous Solutions of Pure Acids and Bases
acidic
– +
+
– +
HA(aq) A–(aq) + H+(aq)
not
B-L definition and reality
amphiprotic (acid and base)
K Kw
H2O(ℓ) + H3O+(aq) + H2O(ℓ) OH–(aq)
H2O H2O [OH–] [H3O+]
initial
Δ
equil
0 0
+x +x
– –
– –
– – x x
x = 1.0 x 10–7 M [H3O+] = [OH–]
= x2 = [H3O+][OH–]
pure water
pure water
Autoprotolysis of Water
autoprotolysis constant
(25 oC)
B + H2O HB+ + OH–
HA + H2O A– + H3O+
–
+
+
=
= 1.0 x 10–14
HA(aq) + H3O+(aq) + H2O(ℓ) A–(aq)
B(aq) HB+(aq) + H2O(ℓ) + OH–(aq)
5
pure water
neutral
[H3O+] > [OH–] [OH–]
acidic
[H3O+] < [OH–] [H3O
+]
basic
[H3O+] = 1.0 x 10–6 M
[OH–] = 1.0 x 10–8 M
acidic
Arrhenius/Brønsted-Lowry Connection
acid
base
(1.0 x 10–6)[OH–] = 1.0 x 10–14
< 1.0 x 10–6 M [H3O
+] = [OH–]
= 1.0 x 10–14 Kw = [H3O+][OH–]
B + H2O HB+ + OH–
HA + H2O A– + H3O+
true for any aqueous solution
= 1.0 x 10–14 Kw = [H3O+][OH–]
= 14.00
= 1.0 x 10–14
= 1.0 x 10–14
6.00
7.00
8.00
1.0 x 10–8
1.0 x 10–7
1.0 x 10–6
1.0 x 10–6
1.0 x 10–7
1.0 x 10–8
0.00 1.0 x 10–14
1.00
2.00
3.00
1.0 x 10–13
1.0 x 10–12
1.0 x 10–11
1.0 x 10–0
1.0 x 10–1
1.0 x 10–2
1.0 x 10–3
4.00 1.0 x 10–10 1.0 x 10–4
5.00 1.0 x 10–9 1.0 x 10–5
9.00 1.0 x 10–5 1.0 x 10–9
10.00 1.0 x 10–4 1.0 x 10–10
11.00
12.00
13.00
14.00
1.0 x 10–3
1.0 x 10–2
1.0 x 10–1
1.0 x 10–0
1.0 x 10–11
1.0 x 10–12
1.0 x 10–13
1.0 x 10–14
pH = 7.00
pH < 7.00
pH > 7.00
neutral
acidic
basic
x
= 1.0 x 10–14
x
x
[H3O+] pH [OH–]
pH
[H3O+] = 2.2 x 10–9 M
pH = 8.65 basic
pH = 5.35
[H3O+] = 10–5.35 = 4.5 x 10–6 M
Søren Sørensen
Danish
(1868-1939)
pH = –log[H3O+]
[H3O+] = 10–pH –log H+
+ pOH = pH pKw
–log(1.0 x 10–8) = 8.00
–log(1.0 x 10–7) = 7.00
–log(1.0 x 10–6) = 6.00
6
pH 0 1 2 3 4 5 6 7 8 9 10 11 12
alizarian yellow R
thymolphthalein
phenolphthalein
thymol blue (base)
phenol red
bromothymol blue
chlorophenol red
bromocresol green
methyl orange
bromophenol blue
thymol blue (acid)
methyl violet
pH can be measured with indicators
Measuring pH
Universal indicator
thin glass membrane
solution of known pH
Ag/AgCl reference
Pt conductor
voltage pH difference
and pH electrodes/meter
H+ H+
H+
H+
H+
H+
H+ H+
H+
H+ H+ H+
H+ H+ H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+ H+
H+
H+
H+
H+ H+
H+
H+
H+
H+
H+
H+ H+ H+
H+ H+
H+
H+
H+
H+
H+
H+ H+
H+
NH3 + H2O NH4+ + OH– N2H4 + H2O N2H5+ + OH– C5H5N + H2O C5H5NH+ + OH–
NH4+ + H2O NH3 + H3O
+ H3PO3 + H2O H2PO3– + H3O
+ HC2H3O2 + H2O C2H3O2– + H3O
+ HCl + H2O Cl– + H3O+ H2SO4 + H2O HSO4
– + H3O+ HC7H5O2 + H2O C7H5O2
– + H3O+
HCl hydrochloric acid H2SO4 sulfuric acid
H3PO3 phosphorous acid HC2H3O2 acetic acid
NH4+ ammonium ion HC7H5O2 benzoic acid
(CH3)3N trimethylamine CH3O– methoxide ion
≥ one H+, often first
neutral or + (and H)
≥ one lone-pair e– (Lewis)
neutral or –, often N or O
acid (HA):
base (B):
NH3 ammonia CO32– carbonate ion
C5H5N pyridine N2H4 hydrazine
Recognizing Acids and Bases
HA + H2O A– + H3O+
(CH3)3N + H2O (CH3)3NH+ + OH– CO32– + H2O HCO3
– + OH– CH3O– + H2O CH3OH + OH– B + H2O HB+ + OH–
7
Cl– chloride
NO2– nitrite
C2H3O2– acetate
hydro_ic
–ous
–ic
–ide
–ite
–ate
acid: CB:
C5H5N pyridine
N2H4 hydrazine
CH3NH2 methylamine CH3NH3+ methylammonium
C5H5NH+ pyridinium
HN2H4+ hydrazinium
CA:
HCl hydrochloric acid
HNO2 nitrous acid
HC2H3O2 acetic acid
base–ium
NH3 ammonia NH4+ ammonium
Recognizing CB and CA From Name
Kb
Ka
pH acid/base reaction [H3O+] K
Acid-Base Equilibrium and pH
HA + H2O A– + H3O+
B + H2O HB+ + OH–
>> 1
<< 1
strong
weak
SA SB
WB WA
K [H3O
+][A–]
[HA] =
[OH–][HB+]
[B] = K
([OH–])
8
complete ionization:
7 common SA: HCl, HBr, HI hydrohalic acids (not HF)
: one H+ strong H2SO4 sulfuric
HNO3 nitric
HClO3, HClO4 chloric, perchloric
Ka = [H3O
+][X–]
[HX] = large
HX + H2O H3O+ + X–
stoichiometry
SA
6 common SA:
0 WA
not SA WA HC2H3O2 acetic HNO2 nitrous HF hydrofluoric
stronger weaker
Ka = [H3O
+][A–]
[HA] = 10–2 to 10–12
Ka = [H3O
+][B]
[HB+] HB+ + H2O B + H3O
+ CA of WB:
H3C CH C
OH O
OH lactic HO C CH2
O
C CH2 C
O
OH
CH2
OH
C O
OH
citric
2 Na+(aq) + O2–(aq) Na2O(aq) 2 Na+(aq) + O2–(aq)
OH– + OH– O2– + H2O 2 OH–
Na2O(aq)
O2– + H2O
NaOH(aq) Na+(aq) + OH–(aq)
2 – –
+
SB
OH–
O2– 2 types SB: ionic
stoichiometry
WB
H H
H
R’ R
R’’
CH3NH2 methylamine
(CH3)2NH dimethylamine
(CH3)3N trimethylamine
NH3
amines
NH2(CH2)4NH2 putracine
N
Kb = [OH–][HB+]
[B] = 10–2 to 10–12
Kb = [OH–][HA]
[A–] HA + OH– A– + H2O CB of WA:
Anthony Ulinski
Na+ (Mn+) not A/B
pyridine C
C N
C
C C
H
H
H H
H
9
6 SA: HCl HBr HI HClO3 HClO4 HNO3
Strong Acids
Weak Acids
if acid, but not SA WA:
Strong Bases
2 SB: ionic OH– ionic O2– (= 2 OH–)
Weak Bases
CA of WB (-ium)
CB of WA (-ide, -ite, -ate)
H-something
-NH2, -NH, -N- if base, but not OH–/O2– WB:
2. write acid-base reaction: CA of SB? pH = OH–
only SB “CA”
H2O 7.00 ?
, SB , WA , WB CB of SA , CB of WA , CA of WB
1. X in one of 7 categories:
pH of X(aq):
SA
3. Ka (WA, CA of WB) or Kb (WB, CB of WA)
pH Calculations
WB WA
,
A H3O+ or B OH–
10
6. (CH2OH)3CNH2
tris(hydroxymethyl)aminomethane
3. NaC7H5O2
sodium benzoate
1. HCl
2. HC8H7O3
mandelic acid
4. NaOH
CaO
7. NH3OH+Cl–
hydroxylammonium chloride
pH Calculations, 0.10 M Solutions of:
5. NaCl
HCl + H2O H3O+ + Cl–
1 HCl 1 H3O+
[H3O+] = [HCl]i = 0.10 M
SA acidic
0.10 M HCl
pH = –log(0.10) = 1.00
11
1. HCl
2. HC8H7O3
mandelic acid
7. NH3OH+Cl–
hydroxylammonium chloride
SA pH = 01.00
3. NaC7H5O2
sodium benzoate
4. NaOH
CaO
6. (CH2OH)3CNH2
tris(hydroxymethyl)aminomethane
5. NaCl
pH Calculations, 0.10 M Solutions of:
Dissociation Constants for Acids at 25 oC.
Name Formula Ka
Acetic HC2H3O2 1.8 x 10–5
Arsenous H3AsO3 5.1 x 10–10
Benzoic HC7H5O2 6.5 x 10–5
Butanoic HC4H7O2 1.5 x 10–5
Chloroacetic HC2H2O2Cl 1.4 x 10–3
Chlorous HClO2 1.1 x 10–2
Cyanic HCNO 3.5 x 10–4
Dichloroacetic HC2HO2Cl2 5.0 x 10–2
Formic HCHO2 1.8 x 10–4
Hydroazoic HN3 1.9 x 10–5
Hydrocyanic HCN 6.2 x 10–10
Hydrofluoric HF 6.8 x 10–4
Hypobromous HBrO 2.3 x 10–9
Hypochlorous HClO 3.0 x 10–8
Hypoiodous HIO 2.3 x 10–11
Iodic HIO3 1.7 x 10–1
Lactic HC3H5O3 1.4 x 10–4
Nitrous HNO2 4.5 x 10–4
Phenol HC6H5O 1.3 x 10–10
Propionic HC3H5O2 1.3 x 10–5
Pyruvic HC3H3O3 2.8 x 10–3
Thiocyanic HSCN 1.3 x 10–1
Dissociation Constants for Bases at 25 oC.
Name Formula Kb
Ammonia NH3 1.8 x 10–5
Aniline C6H5NH2 4.3 x 10–10
Dimethylamine (CH3)2NH 5.4 x 10–4
Ethylamine C2H5NH2 6.4 x 10–4
Hydrazine NH2NH2 1.3 x 10–6
Hydroxylamine NH2OH 1.1 x 10–8
Methylamine CH3NH2 4.4 x 10–4
Pyridine C5H5N 1.7 x 10–9
Trimethylamine (CH3)3N 6.4 x 10–5
Tris (HOCH2)3CNH2 1.2 x 10–6
0.10 M HC8H7O3
x = [H3O+]
x2 + (1.4 x 10–4)x – (1.4 x 10–5) = 0
Ka = (x)(x)
(0.10 – x) =
[H3O+][C8H7O3
–]
[HC8H7O3]
pH = –log(3.7 x 10–3) = 2.43
x = 3.7 x 10–3 M, –7.6 x 10–3 M
(assumption good)
; x = 3.7 x 10–3 M assume x << 0.10: x2
0.10 – x
x2
0.10 ≈ = 1.4 x 10–4
HC8H7O3 + H2O H3O+ + C8H7O3
–
WA acidic
Mandelic HC8H7O3 1.4 x 10–4
–
–
–
H2O
x x 0.10 – x equil
+x +x –x D
0 ~0 0.10 initial
[C8H7O3–] [H3O
+] [HC8H7O3]
= 1.4 x 10–4
12
1. HCl
2. HC8H7O3
mandelic acid
7. NH3OH+Cl–
hydroxylammonium chloride
SA pH = 01.00
WA pH = 02.43
3. NaC7H5O2
sodium benzoate
4. NaOH
CaO
6. (CH2OH)3CNH2
tris(hydroxymethyl)aminomethane
5. NaCl
pH Calculations, 0.10 M Solutions of:
HC7H5O2
Dissociation Constants for Acids at 25 oC.
Name Formula Ka
Acetic HC2H3O2 1.8 x 10–5
Arsenous H3AsO3 5.1 x 10–10
Butanoic HC4H7O2 1.5 x 10–5
Chloroacetic HC2H2O2Cl 1.4 x 10–3
Chlorous HClO2 1.1 x 10–2
Cyanic HCNO 3.5 x 10–4
Dichloroacetic HC2HO2Cl2 5.0 x 10–2
Formic HCHO2 1.8 x 10–4
Hydroazoic HN3 1.9 x 10–5
Dissociation Constants for Bases at 25 oC.
Name Formula Kb
Ammonia NH3 1.8 x 10–5
Aniline C6H5NH2 4.3 x 10–10
Dimethylamine (CH3)2NH 5.4 x 10–4
Ethylamine C2H5NH2 6.4 x 10–4
Hydrazine NH2NH2 1.3 x 10–6
Hydroxylamine NH2OH 1.1 x 10–8
Methylamine CH3NH2 4.4 x 10–4
Pyridine C5H5N 1.7 x 10–9
Trimethylamine (CH3)3N 6.4 x 10–5
Tris (HOCH2)3CNH2 1.2 x 10–6
0.10 M NaC7H5O2
Na+(aq) + C7H5O2–(aq)
+ OH– + H2O HC7H5O2
NaC7H5O2(aq)
basic CB of WA
CB/CA not in table + H3O+ + H2O C7H5O2
–
Kb = ?
Ka = 6.5 x 10–5
[H3O+][C7H5O2
–]
[HC7H5O2]
[OH–][HC7H5O2]
[C7H5O2–]
x = [H3O+][OH–] = Kw
KaKb = 1.0 x 10–14
C A/B pair
here, A stronger than CB: inverse relationship
= 1.5 x 10–10 Kb C7H5O2–
1.0 x 10–14
6.5 x 10–5 =
Kw
Ka HC7H5O2 =
0.10 M NaC7H5O2
C7H5O2–
Benzoic HC7H5O2 6.5 x 10–5
+
13
–
–
–
H2O
x x 0.10 – x equil
+x +x –x D
0 ~0 0.10 initial
[HC7H5O2] [OH–] [C7H5O2–]
x = [OH–]
C7H5O2– + H2O OH– + HC7H5O2
x = 3.9 x 10–6 M = [OH–]
pH = 14.00 – 5.41 = 8.59
; pOH = 5.41
assume x small: x2
0.10 – x
x2
0.10 ≈ = 1.5 x 10–10
Kb (x)(x)
(0.10 – x) =
[OH–][HC7H5O2]
[C7H5O2–]
=
0.10 M NaC7H5O2
= 1.5 x 10–10
= 1.5 x 10–10
1. HCl
2. HC8H7O3
mandelic acid
7. NH3OH+Cl–
hydroxylammonium chloride
SA pH = 01.00
WA pH = 02.43
CB of WA pH = 08.59 3. NaC7H5O2
sodium benzoate
4. NaOH
CaO
6. (CH2OH)3CNH2
tris(hydroxymethyl)aminomethane
5. NaCl
pH Calculations, 0.10 M Solutions of:
14
[OH– ] = [NaOH]i = 0.10 M
pOH = 1.00 ; pH = 13.00
SB basic
NaOH Na+ + OH–
O2– + H2O 2 OH–
CaO Ca2+ + O2–
[OH– ] = 2 x [CaO]i = 0.20 M
pOH = 0.70 ; pH = 13.30
0.10 M NaOH; 0.10 M CaO
1. HCl
6. (CH2OH)3CNH2
tris(hydroxymethyl)aminomethane
7. NH3OH+Cl–
hydroxylammonium chloride
SA pH = 01.00
SB pH = 13.30
SB pH = 13.00
2. HC8H7O3
mandelic acid
WA pH = 02.43
5. NaCl
CB of WA pH = 08.59 3. NaC7H5O2
sodium benzoate
4. NaOH
CaO
pH Calculations, 0.10 M Solutions of:
15
Cl– + H2O HCl + OH–
KaKb = Kw
Ka large , Kb very small ; not basic
NaCl Na+ + Cl–
pH = 7.00
(pure water)
0.10 M NaCl
as Na+ and K+ salts
6 CB of SA: Cl–, Br–, I–, ClO3–, ClO4
–, NO3–
CB of SA (HCl)
1. HCl
6. (CH2OH)3CNH2
tris(hydroxymethyl)aminomethane
7. NH3OH+Cl–
hydroxylammonium chloride
SA pH = 01.00
2. HC8H7O3
mandelic acid
WA pH = 02.43
5. NaCl
CB of WA pH = 08.59 3. NaC7H5O2
sodium benzoate
4. NaOH
CaO SB pH = 13.30
SB pH = 13.00
CB of SA pH = 07.00
pH Calculations, 0.10 M Solutions of:
16
Dissociation Constants for Acids at 25 oC.
Name Formula Ka
Acetic HC2H3O2 1.8 x 10–5
Arsenous H3AsO3 5.1 x 10–10
Benzoic HC7H5O2 6.5 x 10–5
Butanoic HC4H7O2 1.5 x 10–5
Chloroacetic HC2H2O2Cl 1.4 x 10–3
Chlorous HClO2 1.1 x 10–2
Cyanic HCNO 3.5 x 10–4
Dichloroacetic HC2HO2Cl2 5.0 x 10–2
Formic HCHO2 1.8 x 10–4
Hydroazoic HN3 1.9 x 10–5
Dissociation Constants for Bases at 25 oC.
Name Formula Kb
Ammonia NH3 1.8 x 10–5
Aniline C6H5NH2 4.3 x 10–10
Dimethylamine (CH3)2NH 5.4 x 10–4
Ethylamine C2H5NH2 6.4 x 10–4
Hydrazine NH2NH2 1.3 x 10–6
Hydroxylamine NH2OH 1.1 x 10–8
Methylamine CH3NH2 4.4 x 10–4
Pyridine C5H5N 1.7 x 10–9
Trimethylamine (CH3)3N 6.4 x 10–5
(CH2OH)3CNH2 + H2O OH– + (CH2OH)3CNH3+
WB basic
0.10 M (CH2OH)3CNH2
–
–
–
x x 0.10 – x
+x +x –x
0 ~0 0.10
x = [OH–]
; pOH = 3.46; pH = 10.54 x = 3.5 x 10–4 M = [OH–]
Kb (x)(x)
(0.10 – x) =
[OH–][RNH3+]
[RNH2] =
x2
0.10 ≈
H2O
equil
D
initial
[RNH3+] [OH–] [RNH2]
Tris (HOCH2)3CNH2 1.2 x 10–6
= 1.2 x 10–6
R
=
(tris(hydroxymethyl)aminomethane)
1. HCl
6. (CH2OH)3CNH2
tris(hydroxymethyl)aminomethane
7. NH3OH+Cl–
hydroxylammonium chloride
SA pH = 01.00
CB of SA pH = 07.00
WB pH = 10.54
2. HC8H7O3
mandelic acid
WA pH = 02.43
5. NaCl
SB pH = 13.30
SB pH = 13.00
CB of WA pH = 08.59 3. NaC7H5O2
sodium benzoate
4. NaOH
CaO
• • H N OH
H
+
H
H N OH
H
pH Calculations, 0.10 M Solutions of:
17
Dissociation Constants for Acids at 25 oC.
Name Formula Ka
Acetic HC2H3O2 1.8 x 10–5
Arsenous H3AsO3 5.1 x 10–10
Benzoic HC7H5O2 6.5 x 10–5
Butanoic HC4H7O2 1.5 x 10–5
Chloroacetic HC2H2O2Cl 1.4 x 10–3
Chlorous HClO2 1.1 x 10–2
Cyanic HCNO 3.5 x 10–4
Dichloroacetic HC2HO2Cl2 5.0 x 10–2
Formic HCHO2 1.8 x 10–4
Hydroazoic HN3 1.9 x 10–5
Dissociation Constants for Bases at 25 oC.
Name Formula Kb
Ammonia NH3 1.8 x 10–5
Aniline C6H5NH2 4.3 x 10–10
Dimethylamine (CH3)2NH 5.4 x 10–4
Ethylamine C2H5NH2 6.4 x 10–4
Hydrazine NH2NH2 1.3 x 10–6
Methylamine CH3NH2 4.4 x 10–4
Pyridine C5H5N 1.7 x 10–9
Trimethylamine (CH3)3N 6.4 x 10–5
Tris (HOCH2)3CNH2 1.2 x 10–6
0.10 M NH3OH+Cl–
NH3OH+Cl– NH3OH+ + Cl–
Kw
Kb NH2OH Ka =
CB of SA not basic CA of WB
+ H2O H3O+ + NH2OH
–
–
–
x x 0.10 – x
+x +x –x
0 ~0 0.10
x = [H3O+]
; pH = 3.52 x = 3.0 x 10–4 M = [H3O+]
x2
0.10 ≈
(x)(x)
(0.10 – x) = Ka =
[H3O+][NH2OH]
[NH3OH+]
= 9.1 x 10–7 1.0 x 10–14
1.1 x 10–8 =
H2O
equil
D
initial
[NH2OH] [H3O+] [NH3OH+]
Hydroxylamine NH2OH 1.1 x 10–8
= 9.1 x 10–7
NH3OH+
WB pH = 10.54
1. HCl
7. NH3OH+Cl–
hydroxylammonium chloride
SA pH = 01.00
CA of WB pH = 03.52
CB of SA pH = 07.00
2. HC8H7O3
mandelic acid
WA pH = 02.43
SB pH = 13.30
SB pH = 13.00
CB of WA pH = 08.59 3. NaC7H5O2
sodium benzoate
4. NaOH
CaO
6. (CH2OH)3CNH2
tris(hydroxymethyl)aminomethane
5. NaCl
pH Calculations, 0.10 M Solutions of:
18
Dissociation Constants for Acids at 25 oC.
Name Formula Ka (or Ka1) Ka2 Ka3
Acetic HC2H3O2 1.8 x 10–5
Arsenic H3AsO4 5.8 x 10–3 1.1 x 10–7 3.2 x 10–12
Arsenous H3AsO3 5.1 x 10–10
Benzoic HC7H5O2 6.5 x 10–5
Boric H3BO3 5.8 x 10–10 1.8 x 10–13 1.6 x 10–14
Butanoic HC4H7O2 1.5 x 10–5
Carbonic H2CO3 4.3 x 10–7 5.6 x 10–11
Chloroacetic HC2H2O2Cl 1.4 x 10–3
Chlorous HClO2 1.1 x 10–2
Citric H3C6H5O7 7.4 x 10–4 1.7 x 10–5 4.0 x 10–7
Cyanic HCNO 3.5 x 10–4
Ka1 > Ka2 H2A + H2O HA– + H3O+ Ka1
HA– + H2O A2– + H3O+ Ka2
H+ donated stepwise: H2A, diprotic acid
Polyprotic Acids
Kb1 > Kb2
HA– + H2O H2A + OH– Kb2
A2– + H2O HA– + OH– Kb1
Ka1Kb2 = Kw
Ka2Kb1 = Kw
A2–
HA–
H2C6H6O6 + H2O H3O+ + HC6H6O6
–
; Ka2 = 1.6 x 10–12 Ka1 = 8.0 x 10–5
; pH = 2.55 ; x = 2.8 x 10–3 M H3O+ Ka1 = 8.0 x 10–5
x2
0.10 ≈
0.10 M H2C6H6O6, ascorbic acid
+ H2O HCO3– + OH–
H2CO3, carbonic acid: ; Ka2 = 5.6 x 10–11 Ka1 = 4.3 x 10–7
; pH = 8.63 ; pOH = 5.37 x = 4.3 x 10–6 M = [OH–]
= 1.8 x 10–4 ; Kb1 = 1.0 x 10–14
5.6 x 10–11 Ka2Kb1 = Kw
x2
0.10 ≈
0.10 M Na2CO3, sodium carbonate
Na2CO3 2 Na+ + CO32–
Ascorbic H2C6H6O6 8.0 x 10–5 1.6 x 10–12