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# pH of Common Acids and Bases

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# pH of Common Acids and Bases

Calculated pH values of common acids and bases for 1, 10, and 100 mmol/L (valid for standard conditions at 25, 1 atm; acidity constants are taken from

here

):

 • acids: sorted by pH or formula • bases: sorted by pH or formula • organics: organic acids and salts
 • other reactions:   Free software  ( Example )     Demo: Online pH-Calculator

pH of Acids – Sorted by pH

Acid Name 1 mM 10 mM 100 mM
H2SeO4 selenic acid 2.74 1.83 0.97
H2SO4 sulfuric acid 2.75 1.87 1.01
HI hydroiodic acid 3.01 2.04 1.08
HBr hydrobromic acid 3.01 2.04 1.08
HCl hydrochloric acid 3.01 2.04 1.08
HNO3 nitric acid 3.01 2.04 1.08
H3PO4 orthophosphoric acid 3.06 2.26 1.63
H3AsO4 arsenic acid 3.08 2.31 1.70
H2SeO3 selenous acid 3.15 2.47 1.90
H2CrO4 chromic acid 3.03 2.33 2.06
H3Citrate citric acid, C6H8O7 3.24 2.62 2.08
HF hydrofluoric acid 3.27 2.65 2.12
HNO2 nitrous acid 3.28 2.67 2.13
HCyanate isocyanic acid, HOCN 3.35 2.76 2.23
HFormate formic acid, CH2O2 (methanoic acid) 3.47 2.91 2.38
H2Se hydrogen selenide 3.49 2.93 2.41
H2MoO4 molybdic acid 3.46 2.94 2.43
HLactate lactic acid, C3H6O3 (milk acid) 3.51 2.96 2.44
HAcetate acetic acid, C2H4O2 (ethanoic acid) 3.91 3.39 2.88
H2CO3 carbonic acid 4.68 4.18 3.68
H2S hydrogen sulfide 4.97 4.47 3.97
H3AsO3 arsenious acid 6.07 5.58 5.09
HCyanide hydrocyanic acid, HCN 6.11 5.62 5.12
H3BO3 boric acid 6.12 5.62 5.12
H4SiO4 silicic acid 6.40 5.91 5.42
H4SiO4 silicic acid (with SiO2(a) precipitation) 6.40 6.26 6.26

pH of Acids – Sorted by Formula

Acid Name 1 mM 10 mM 100 mM
H2CO3 carbonic acid 4.68 4.18 3.68
H2CrO4 chromic acid 3.03 2.33 2.06
H2MoO4 molybdic acid 3.46 2.94 2.43
H2S hydrogen sulfide 4.97 4.47 3.97
H2Se hydrogen selenide 3.49 2.93 2.41
H2SeO3 selenous acid 3.15 2.47 1.90
H2SeO4 selenic acid 2.74 1.83 0.97
H2SO4 sulfuric acid 2.75 1.87 1.01
H3AsO3 arsenious acid 6.07 5.58 5.09
H3AsO4 arsenic acid 3.08 2.31 1.70
H3BO3 boric acid 6.12 5.62 5.12
H3Citrate citric acid, C6H8O7 3.24 2.62 2.08
H3PO4 orthophosphoric acid 3.06 2.26 1.63
H4SiO4 silicic acid 6.40 5.91 5.42
H4SiO4 silicic acid (with SiO2(a) precipitation) 6.40 6.26 6.26
HAcetate acetic acid, C2H4O2 (ethanoic acid) 3.91 3.39 2.88
HBr hydrobromic acid 3.01 2.04 1.08
HCl hydrochloric acid 3.01 2.04 1.08
HCyanate isocyanic acid, HOCN 3.35 2.76 2.23
HCyanide hydrocyanic acid, HCN 6.11 5.62 5.12
HF hydrofluoric acid 3.27 2.65 2.12
HFormate formic acid, CH2O2 (methanoic acid) 3.47 2.91 2.38
HI hydroiodic acid 3.01 2.04 1.08
HLactate lactic acid, C3H6O3 (milk acid) 3.51 2.96 2.44
HNO2 nitrous acid 3.28 2.67 2.13
HNO3 nitric acid 3.01 2.04 1.08

pH of Bases – Sorted by pH

The limited solubility of hydroxides is taken into account (as indicated by footnotes in the last column).

Base Name 1 mM 10 mM 100 mM
Ba(OH)2 barium hydroxide 11.27 12.22 13.08

1

Sr(OH)2 strontium hydroxide 11.27 12.22 13.09
NaOH sodium hydroxide 10.98 11.95 12.88
KOH potassium hydroxide (caustic potash) 10.98 11.95 12.88
Na2SiO3 sodium metasilicate 11.00 11.91 12.62
Ca(OH)2 calcium hydroxide (lime, CaO:H2O) 11.27 12.20 12.46

2

Na3PO4 trisodium phosphate 10.95 11.71 12.12
K2CO3 potassium carbonate 10.52 11.00 11.36
Na2CO3 sodium carbonate (soda ash) 10.52 10.97 11.26
NH4OH ammonium hydroxide (NH3:H2O) 10.09 10.61 11.12
Mg(OH)2 magnesium hydroxide (MgO:H2O) 10.40 10.40 10.40

3

CaCO3 calcium carbonate (calcite) 9.91 9.91 9.91

4

Fe(OH)2 iron(II) hydroxide (ferrous hydroxide) 9.45 9.45 9.45

5

Cd(OH)2 cadmium hydroxide 9.36 9.36 9.36

6

Na2B4O7 sodium borate (borax) 9.21 9.17 9.05
Co(OH)2 cobalt(II) hydroxide 9.15 9.15 9.15

7

Zn(OH)2 zinc hydroxide 8.88 8.88 8.88

8

Ni(OH)2 nickel(II) hydroxide 8.37 8.37 8.37

9

KAcetate potassium acetate (CH3COOK) 7.87 8.33 8.75
NaAcetate sodium acetate (CH3COONa) 7.87 8.33 8.75
KHCO3 potassium hydrogen carbonate 8.27 8.25 8.13
NaHCO3 sodium hydrogen carbonate 8.27 8.22 8.02
Be(OH)2 beryllium hydroxide 7.90 7.90 7.90

10

Cu(OH)2 copper(II) hydroxide 7.69 7.69 7.69

11

Pb(OH)2 lead(II) hydroxide 7.54 7.54 7.54

12

Cr(OH)3 chromium(III)hydroxide 7.04 7.04 7.04

13

Hg(OH)2 mercury(II) hydroxide 7.03 7.03 7.03

14

pH of Bases – Sorted by Formula

Base Name 1 mM 10 mM 100 mM
Ba(OH)2 barium hydroxide 11.27 12.22 13.08

1

Be(OH)2 beryllium hydroxide 7.90 7.90 7.90

10

Ca(OH)2 calcium hydroxide (lime, CaO:H2O) 11.27 12.20 12.46

2

CaCO3 calcium carbonate (calcite) 9.91 9.91 9.91

4

Cd(OH)2 cadmium hydroxide 9.36 9.36 9.36

6

Co(OH)2 cobalt(II) hydroxide 9.15 9.15 9.15

7

Cr(OH)3 chromium(III) hydroxide 7.04 7.04 7.04

13

Cu(OH)2 copper(II) hydroxide 7.69 7.69 7.69

11

Fe(OH)2 iron(II) hydroxide (ferrous hydroxide) 9.45 9.45 9.45

5

Hg(OH)2 mercury(II) hydroxide 7.03 7.03 7.03

14

K2CO3 potassium carbonate 10.52 11.00 11.36
KAcetate potassium acetate (CH3COOK) 7.87 8.33 8.75
KHCO3 potassium hydrogen carbonate 8.27 8.25 8.13
KOH potassium hydroxide (caustic potash) 10.98 11.95 12.88
Mg(OH)2 magnesium hydroxide (MgO:H2O) 10.40 10.40 10.40

3

Na2B4O7 sodium borate (borax) 9.21 9.17 9.05
Na2CO3 sodium carbonate (soda ash) 10.52 10.97 11.26
Na2SiO3 sodium metasilicate 11.00 11.91 12.62
Na3PO4 trisodium phosphate 10.95 11.71 12.12
NaAcetate sodium acetate (CH3COONa) 7.87 8.33 8.75
NaHCO3 sodium hydrogen carbonate 8.27 8.22 8.02
NaOH sodium hydroxide 10.98 11.95 12.88
NH4OH ammonium hydroxide (NH3:H2O) 10.09 10.61 11.12
Ni(OH)2 nickel(II) hydroxide 8.37 8.37 8.37

9

Pb(OH)2 lead(II) hydroxide 7.54 7.54 7.54

12

Sr(OH)2 strontium hydroxide 11.27 12.22 13.09
Zn(OH)2 zinc hydroxide 8.88 8.88 8.88

8

Remarks & Footnotes

Hydroxides are strong bases but have low solubility which confines the pH to an upper bound. This is achieved by including the corresponding solid phase into the equilibrium calculation.

1. in equilibrium with solid phase Ba(OH)2:8H2O

2

2. in equilibrium with solid phase Portlandite

2

3. in equilibrium with solid phase Brucite

2

4. in equilibrium with solid phase Calcite

2

5. in equilibrium with solid phase Fe(OH)2

2

6. in equilibrium with solid phase Cd(OH)2

2

7. in equilibrium with solid phase Co(OH)2

2

8. in equilibrium with solid phase Zn(OH)2-c

2

9. in equilibrium with solid phase Ni(OH)2

2

10. in equilibrium with solid phase Be(OH)2

2

11. in equilibrium with solid phase Cu(OH)2

2

12. in equilibrium with solid phase Pb(OH)2

2

13. in equilibrium with solid phase Cr(OH)3(a)

2

14. in equilibrium with solid phase Hg(OH)2

2