Strong acid and bases - Weak acid and bases - Dissociation constants and pK's
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Table I.1: Strong acids in aqueous
solutions
|
Compound
|
ka
|
pka
|
Acetic
acid (CH3COOH)
|
1.76
x 10-5
|
4.75
|
Adipic
acid (CH2)4(COOH)2
|
3.71
x 10-5 Step 1
3.87
x 10-5 Step 2
|
4.43
4.41
|
Benzoic
acid (C6H5COOH)
|
6.46
x 10-5
|
4.19
|
Carbonic
acid (H2CO3)
|
4.3
x 10-7
5.61
x 10-11
|
6.37
10.25
|
Chloroacetic
acid (ClCH2CO2H)
|
1.4
x 10-3
|
2.85
|
Chromic
acid (H2CrO4)
|
1.8
x 10-1
3.2
x 10-7
|
0.74
6.49
|
Formic
acid (HCOOH)
|
1.77
x 10-4 (20 ○C)
|
3.75
|
Hydrocyanic
acid (HCN)
|
4.93
x 10-10
|
9.31
|
Hydrofluoric
acid (HF)
|
3.53
x 10-4
|
3.45
|
Hypobromous
acid (HBrO)
|
2.06
x 10-9
|
8.69
|
Hypochlorous
acid (HClO)
|
2.95
x 10-8
|
7.53
|
Hypoiodous
acid (HIO)
|
2.3
x 10-11
|
10.64
|
Iodic
acid (HIO3)
|
1.69
x 10-1
|
0.77
|
Maleic
acid
|
1.42
x 10-2
8.57
x 10-7
|
1.83
6.07
|
Nitrous
acid (HNO2)
|
4.6
x 10-4 (12,5 ○C)
|
3.37
|
Oxalic
acid (H2C2O4)
|
5.90
x 10-2
6.40
x 10-5
|
1.23
4.19
|
Periodic
acid
|
2.3
x 10-2
|
1.64
|
Phenol
(C6H5OH)
|
1.28
x 10-10
|
9.89
|
o-Phosphoric
acid (H3PO4)
|
7.52
x 10-3
6.23
x 10-8
|
2.12
7.21
|
Strong
bases in aqueous solutions
|
|
Group
1A metal hydroxides
|
LiOH,
NaOH, KOH, RbOH, CsOH
|
Group 2A metal hydroxides
|
Ca(OH)2,
Sr(OH)2, Ba(OH)2
|
Compound
|
kb
|
pkb
|
Acetamide
(CH3CONH2)
|
2.5
x 10-13
|
12.60
|
Acetanilide
(CH3CONHPh)
|
4.1
x 10-14
|
13.39
|
Ammonium
hydroxide (NH4OH)
|
1.79
x 10-5
|
4.75
|
Diethylamine
(C2H5NHC2H5)
|
9.6
x 10-4
|
3.02
|
n-Diethylamine
|
3.65
x 10-8
|
7.44
|
Glycine
|
2.26
x 10-12
|
11.65
|
Methylamine
|
4.38
x 10-4
|
3.36
|
What ranges of ka values characterize strong and weak acids? What are the corresponding degree of dissociation α values?
Type
of acid
|
ka
|
pka
|
Degree of dissociation (α) of acid (%)
|
Very
strong acid
|
> 0.1
|
< 1
|
90-100%
|
Moderately
strong acid
|
10-3 – 0.1
|
1-3
|
30-90%
|
Weak
acid
|
10-5 – 10-3
|
3-5
|
30-5%
|
Very
weak acid
|
10-15 – 10-5
|
5-15
|
5-1%
|
Extremely
weak acid
|
< 10-15
|
> 15
|
< 1%
|
Why proton transfers occur in acid-base reactions?
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Fig. I.1: Formation
of products - H3O+
transfer – is highly favored in the ionization of HCl in water due to the lower
energy attained. The ΔG
for the reaction is -40 kJ/mol.
|
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Fig. I.2: Proton solvated – attached to water
molecules
|
Relevant Posts - Relevant Videos
Ionic equilibrium - A general expression of the pH of a strong acid
Chemical Equilibrium Calculations in Analytical Chemistry
pH of a strong acid – Examples
Strong Acids & Bases: pH Calculations involving mixtures of strong acids and bases
References
- J-L. Burgot “Ionic Equilibria in Analytical Chemistry”,Springer Science & Business Media, 2012
- J.N. Butler “Ionic Equilibrium – Solubility and pH calculations”, Wiley – Interscience, 1998
- Clayden,Greeves, Waren and Wothers “Organic Chemistry”, Oxford, 2012
- D. Harvey,“Modern Analytical Chemistry”, McGraw-Hill Companies Inc., 2000
- Toratane Munegumi, World J. of Chem. Education, 1.1, 12 (2013)
Key Terms
strong acid, strong base, pH calculation, [H+] concentration, pH, Kw, calculate the pH of a strong acid, calculate the pH of a strong base, strong acids and bases,pH of a strong acid, pH of a strong base,pH of a weak acid, pH of a weak base, ionic equilibrium, conjugate base, conjugate acid, dissociation constant, degree of dissociation,hydroxyl ion, hydronium ion
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