Appendix C

C9 Ka and Kb for Common Acids and Weak Bases Monoprotic Acids

Name perchloric acid hydroiodic acid hydrobromic acid hydrochloric acid nitric acid hydronium ion iron(III) ion citric acid nitrous acid hydrofluoric acid hydrogen cyanate methanoic acid chromium(III) ion methyl orange benzoic acid ethanoic (acetic) acid aluminum ion bromothymol blue hypochlorous acid phenolphthalein hydrocyanic acid ammonium ion boric acid phenol hydrogen peroxide water hydroxide ion

Weak Bases

Formula of Acid HClO4(aq) HI(aq) HBr(aq) HCl(aq) HNO3(aq) H3O+(aq) 3+ Fe(H2O)6 (aq) H3C6H5O7(aq) HNO2(aq) HF(aq) HOCN HCHO2; HCOOH(aq) 3+ Cr(H2O)6 (aq) HMo(aq) HC7H5O2(aq); C6H5COOH(aq) HC2H3O2(aq); CH3COOH(aq) 3+ Al(H2O)6 (aq) HBb(aq) HClO(aq) HPh(aq) HCN(aq) + NH4 (aq) H3BO3(aq) C6H5OH(aq) H2O2(aq) H2O(l) – OH(aq)

Formula of Conjugate Base ClO4–(aq) I–(aq) Br–(aq) Cl–(aq) NO3–(aq) H20(l) Fe(H2O)5(OH)2+ (aq) H2C6H5O7–(aq) NO2–(aq) F–(aq) OCN–(aq) CHO2–(aq) Cr(H2O)5(OH) 2+ (aq) – Mo(aq) – C6H5O2(aq) – C2H3O2(aq) 2+ Al(H2O)5(OH)(aq) – Bb(aq) – ClO(aq) – Ph(aq) – CN(aq) NH3(aq) – H2BO3(aq) – C6H5O(aq) – HO2(aq) – OH(aq) 2– O (aq)

Equilibrium Constant, K a very large very large very large very large very large 1.0 1.5 x 10–3 7.4 x 10–4 7.2 x 10–4 6.6 x 10–4 3.5 x 10–4

Name

Formula

Equilibrium Constant, K b

dimethylamine methylamine ethylamine trimethylamine ammonia hydrazine hydroxylamine pyridine aniline

CH3CH3NH CH3NH2 CH3CH2NH2 CH3CH3CH3N NH3 N2H4 NH2OH C5H5N C5H5NH2

9.6  104 4.4  104 4.3  104 7.4  105 1.8  105 9.6  107 6.6  109 1.5  109 4.1  1010

1.8 x 10–4 1.0 x 10–4 ~10–4 6.3 x 10–5 1.8 x 10–5 9.8 x 10–6 ~10–7 2.9 x 10–8 ~10–10 6.2 x 10–10 5.8 x 10–10 5.8 x 10–10 1.0 x 10–10 2.2 x 10–12 1.0 x 10–14 very small

• Values in this table are taken from Lange’s Handbook of Chemistry, 13th Edition for 25°C.

Polyprotic Acids

Name

Formula of Acid

Formula of Conjugate Base

sulfuric acid oxalic acid sulfurous acid (SO2 + H2O) phosphoric acid carbonic acid (CO2 + H2O) hydrosulfuric acid

H2SO4(aq) H2C2O4(aq); HOOCCOOH(aq) H2SO3(aq) H3PO4(aq) H2CO3(aq) H2S(aq)

– HSO4(aq) – HC2O4 (aq) – HSO3(aq) – H2PO4(aq) – HCO3(aq) – HS(aq)

Ka1

Equilibrium Constant Ka2 Ka3

very large 5.4 x 10–2 1.3 x 10–2 7.1 x 10–3 4.4 x 10–7 1.1 x 10–7

1.0 x 10–2 5.4 x 10–5 6.2 x 10–8 6.3 x 10–8 4.7 x 10–11 1.3 x 10–13

4.2 x 10–13

• Values in this table are taken from Lange’s Handbook of Chemistry, 13th Edition for 25°C.

NEL

Reference 803

C