100 Most Common Acids & Bases

100 Most Common Acids & Bases with Strength

🔹Strong Acids (Completely Ionized in Water)

(Extremely low pKa, < –1)

1. HCl – Hydrochloric acid (strong)

2. HBr – Hydrobromic acid (strong)

3. HI – Hydroiodic acid (strong)

4. HNO₃ – Nitric acid (strong)

5. HClO₄ – Perchloric acid (very strong)

6. HClO₃ – Chloric acid (strong)

7. H₂SO₄ – Sulfuric acid (first proton strong, pKa ≈ –3)

8. HBrO₄ – Perbromic acid (strong)

9. HIO₄ – Periodic acid (strong)

10. H₂SeO₄ – Selenic acid (strong)

🔹Moderately Strong Acids

(pKa ≈ 0 to +3, partially ionized)

11. H₃PO₄ – Phosphoric acid (pKa₁ ≈ 2.1, weak for further protons)

12. H₂SO₃ – Sulfurous acid (pKa₁ ≈ 1.9, weak)

13. HF – Hydrofluoric acid (weak compared to HCl, pKa ≈ 3.2)

14. HNO₂ – Nitrous acid (pKa ≈ 3.3)

15. HCN – Hydrocyanic acid (weak, pKa ≈ 9.2 but important)

16. HClO₂ – Chlorous acid (pKa ≈ 1.9)

17. HClO – Hypochlorous acid (pKa ≈ 7.5, weak oxidizing acid)

18. H₂CO₃ – Carbonic acid (pKa₁ ≈ 6.3, weak)

19. H₂C₂O₄ – Oxalic acid (pKa₁ ≈ 1.3, strong weak acid)

20. H₂CrO₄ – Chromic acid (moderate)

🔹 Weak Organic Acids (Carboxylic & Phenolic, pKa 3–6)

21. HCOOH – Formic acid (pKa ≈ 3.7)

22. CH₃COOH – Acetic acid (pKa ≈ 4.7)

23. C₂H₅COOH – Propionic acid (pKa ≈ 4.9)

24. C₆H₅COOH – Benzoic acid (pKa ≈ 4.2)

25. Lactic acid (C₃H₆O₃, pKa ≈ 3.8)

26. Tartaric acid (C₄H₆O₆, diprotic, pKa₁ ≈ 3.0)

27. Citric acid (C₆H₈O₇, triprotic, pKa₁ ≈ 3.1)

28. Succinic acid (C₄H₆O₄, diprotic, pKa₁ ≈ 4.2)

29. Maleic acid (cis-C₄H₄O₄, pKa₁ ≈ 1.9)

30. Fumaric acid (trans-C₄H₄O₄, pKa₁ ≈ 3.0)

🔹Phenols & Weak Aromatic Acids

(pKa ≈ 9–10, weaker than carboxylic acids)

31. C₆H₅OH – Phenol (pKa ≈ 10)

32. o-Nitrophenol (pKa ≈ 7.2, stronger due to –NO₂)

33. p-Nitrophenol (pKa ≈ 7.1)

34. Cresol (CH₃–C₆H₄–OH, pKa ≈ 10.2)

35. Resorcinol (pKa ≈ 9.3)

36. Hydroquinone (pKa ≈ 10.0)

37. Picric acid (2,4,6-trinitrophenol, pKa ≈ 0.4, strong organic acid)

38. Salicylic acid (o-HO–C₆H₄–COOH, pKa ≈ 2.9)

39. Ascorbic acid (Vitamin C, pKa ≈ 4.2, 11.6)

40. Uric acid (pKa ≈ 5.4, weak diprotic)

🔹 Bases – Strong (Completely Ionized in Water)

(Low pKb, very basic)

41. NaOH – Sodium hydroxide (strong base)

42. KOH – Potassium hydroxide (strong)

43. LiOH – Lithium hydroxide (strong)

44. RbOH – Rubidium hydroxide (strong)

45. CsOH – Cesium hydroxide (strong)

46. Ca(OH)₂ – Calcium hydroxide (strong but less soluble)

47. Sr(OH)₂ – Strontium hydroxide (strong)

48. Ba(OH)₂ – Barium hydroxide (strong)

49. Mg(OH)₂ – Magnesium hydroxide (sparingly soluble)

50. TlOH – Thallium hydroxide (strong)

🔹Weak Inorganic Bases

(Partially ionized, pKb \~ 4–10)

51. NH₃ – Ammonia (weak base, pKb ≈ 4.7)

52. NH₄OH – Ammonium hydroxide (weak)

53. CaCO₃ – Calcium carbonate (acts as base, weak)

54. Na₂CO₃ – Sodium carbonate (moderately strong base)

55. NaHCO₃ – Sodium bicarbonate (weak amphoteric base)

56. Al(OH)₃ – Aluminium hydroxide (weak base, amphoteric)

57. Zn(OH)₂ – Zinc hydroxide (amphoteric)

58. Pb(OH)₂ – Lead hydroxide (weak base)

59. Fe(OH)₂ – Iron(II) hydroxide (weak)

60. Fe(OH)₃ – Iron(III) hydroxide (weak)

🔹Organic Amines (Weak to Moderate Bases)

(pKb ≈ 3–5 for aliphatic, 8–10 for aromatic)

61. CH₃NH₂ – Methylamine (weak base, pKb ≈ 3.4)

62. C₂H₅NH₂ – Ethylamine (weak base)

63. (CH₃)₂NH – Dimethylamine (pKb ≈ 3.3, stronger)

64. (CH₃)₃N – Trimethylamine (pKb ≈ 4.2)

65. C₆H₅NH₂ – Aniline (aromatic, weak base, pKb ≈ 9.4)

66. o-Toluidine (pKb ≈ 9.3)

67. p-Toluidine (pKb ≈ 9.2)

68. Pyridine (C₅H₅N, pKb ≈ 8.8, weak base)

69. Quinoline (heterocyclic base, pKb ≈ 9.2)

70. Imidazole (moderate base, pKa ≈ 7.0 for conjugate acid)

🔹 Biological / Biochemically Relevant Bases

71. Adenine (weak base, pKb ≈ 4)

72. Guanine (weak base, nucleobase)

73. Cytosine (moderate base)

74. Thymine (weak base)

75. Uracil (weak base)

76. Histidine (imidazole group, amphoteric, pKa ≈ 6.0)

77. Lysine (–NH₂ group, strongly basic, pKa ≈ 10.5)

78. Arginine (guanidino group, strong base, pKa ≈ 12.5)

79. Tyrosine (phenolic group, weak acid/base balance)

80. Cysteine (thiol group, weak acid/base)

🔹Amphoteric Compounds (Act as Acid & Base Both)

81. H₂O – Water (neutral, amphoteric)

82. NH₃ – Ammonia (weak base, conjugate acid NH₄⁺ weak acid)

83. HCO₃⁻ – Bicarbonate ion

84. HSO₄⁻ – Bisulfate ion

85. H₂PO₄⁻ – Dihydrogen phosphate

86. HPO₄²⁻ – Hydrogen phosphate

87. ZnO – Zinc oxide (amphoteric)

88. Al₂O₃ – Aluminium oxide (amphoteric)

89. PbO – Lead(II) oxide (amphoteric)

90. Cr(OH)₃ – Chromium(III) hydroxide (amphoteric)

🔹Other Important Acids

91. H₂S – Hydrosulfuric acid (weak, pKa ≈ 7.0)

92. H₂Se – Hydroselenic acid (stronger, pKa ≈ 3.9)

93. H₂Te – Hydrotelluric acid (stronger, pKa ≈ 2.6)

94. HClO₄ derivatives (very strong oxidizing acids)

95. HBrO₃ – Bromic acid (moderate strong)

96. HIO₃ – Iodic acid (moderate strong)

97. H₂MnO₄ – Manganic acid (weak)

98. HMnO₄ – Permanganic acid (strong oxidizing)

99. HReO₄ – Perrhenic acid (very strong)

100. H₂SiF₆ – Fluorosilicic acid (strong acid in Industry)

🔥 Interesting Facts About Acids & Bases

🧪 Acids

1. Strongest Simple Acid in Water Perchloric acid (HClO₄) is often considered the strongest acid in aqueous solutions.

2. HF is weaker than HCl– Hydrofluoric acid (HF) is weaker than HCl, HBr, HI, because of very strong H–F bond (harder to break).

3. “Superacids”– Acids stronger than 100% sulfuric acid. Example: Fluoroantimonic acid (HSbF₆), over a billion times stronger than H₂SO₄.

4. Natural Acid in Fruits – Citric acid (lemons, oranges), malic acid (apples), tartaric acid (grapes), ascorbic acid (Vitamin C).

5. Acid in Ants – Formic acid (HCOOH) is present in ant stings.

6. Stomach Acid– Human stomach contains HCl with pH ~1.5–3.5.

7. Acid Rain – Caused by H₂SO₄ and HNO₃ formed from SO₂ and NOx in the atmosphere.

8. Picric Acid (2,4,6-trinitrophenol) – One of the strongest organic acids, also used in explosives.

9. Carbonic Acid (H₂CO₃) – Weak acid but very important, it maintains blood pH balance.

10. Vinegar– Dilute solution of acetic acid (CH₃COOH, \~5–8%).

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🧪 Bases

11. Strongest Base in Water– Cesium hydroxide (CsOH) and other alkali hydroxides are very strong.

12. Superbases– Bases stronger than OH⁻, like lithium diisopropylamide (LDA) or sodium hydride (NaH).

13. Ammonia – A weak base but industrially very important (fertilizers, cleaning).

14. Baking Soda – Sodium bicarbonate (NaHCO₃) is a weak base used in baking and medicine (antacid).

15. Milk of Magnesia– Magnesium hydroxide suspension, used to neutralize stomach acid.

16. Soap is Basic– Soap solutions are basic because of sodium salts of fatty acids.

17. Strongest Known Base– The ortho-diethynylbenzene dianion (very strong, exists only in special conditions).

18. Egg Whites– Slightly basic (pH ~8).

19. Blood – Slightly basic with pH ~7.35–7.45.

20. Amphoteric Nature– Some hydroxides/oxides like Al(OH)₃, ZnO act both as acid and base.

⚖️ General Acid–Base Facts

21. pH Scale – Runs from 0 (strongly acidic) to 14 (strongly basic), with 7 as neutral.

22. Negative pH – Extremely strong acids can have pH < 0(e.g., concentrated HCl).

23. pH of Concentrated NaOH – Can reach up to ~15 (very basic).

24. Acid–Base Indicators – Litmus turns red in acid, blue in base.

25. Universal Indicator– Shows a range of colors for different pH values.

26. Self-Ionization of Water – At 25°C, [H⁺] = [OH⁻] = 10⁻⁷ M, giving neutral pH = 7.

27. Bronsted vs. Lewis Acids/Bases – Bronsted defines by proton transfer, Lewis by electron pair transfer.

28. Conjugate Rule – Strong acids have very weak conjugate bases (e.g., Cl⁻), and strong bases have very weak conjugate acids (e.g., Na⁺).

29. Acid–Base in Space – On Venus, the atmosphere has H₂SO₄ clouds – acid rain, but it evaporates before hitting the surface.

30. pKa & Strength – Lower pKa = stronger acid; lower pKb = stronger base.