1)Sulfurous acid 3 Instability: H,SO,=H,0+S0, Acidity:K1=13×102,K2=6.2×108 3 Oxidizing/reducing properties EA0:SO420158H2O30449s EB:SO42-0.936S032059S Reducing properties 厶 In acidic medium I2+SO +H,0=SO4+2r+2Ht 5S032-+2MnO4+6H*=2Mn2*+5S042-+3H20 2H2SO3+ O2=2H2SO4 AIn ba asic meaium SO32+12+2OH=SO4 +21+H2O Oxidizing properties H2SO3+2H2S=3S↓+3H2O 2) Sulfites 6 Solubility: Acid salts and some normal salts(K+, Nat, NH4) will be readily soluble, others will be insoluble CaSO3+ SO2+H2o= Ca(HSO3) 3 Thermal stability 4Na2SO3 A> 3 Na2SO4+ Na2S 3 Reducing properties 秀 Identification of 2Na2SO3+O2→2Na2SO SO32+2H=H2SO3→SO2↑H2O The test paper of fuchsine: red- colorless 2. Sulfuric acid and sulfates 第17页 2006-02-22第 17 页 2006-02-22 17 1) Sulfurous acid ○ 1 Instability: H2SO3 = H2O + SO2 ○ 2 Acidity: K1 θ =1.3×10-2, K2 θ =6.2×10-8 ○ 3 Oxidizing/reducing properties EA θ : SO4 2- 0.158 H2SO3 0.449 S EB θ : SO4 2- -0.936 SO3 2- -0.59 S Reducing properties: △1 In acidic medium: I2 + SO3 2- + H2O = SO4 2- + 2I- + 2H+ 5SO3 2-+2MnO4 - +6H+ =2Mn2++5SO4 2-+ 3H2O 2H2SO3 + O2 = 2H2SO4 △2 In basic medium: SO3 2- + I2 + 2OH- = SO4 2- +2I- + H2O Oxidizing properties: H2SO3 + 2H2S = 3S↓ + 3H2O 2) Sulfites ○ 1 Solubility: Acid salts and some normal salts (K+ , Na+ , NH4 + ) will be readily soluble, others will be insoluble CaSO3 + SO2 + H2O = Ca(HSO3)2 ○ 2 Thermal stability 4Na2SO3 →Δ 3 Na2SO4 + Na2S ○ 3 Reducing properties 2Na2SO3 + O2 → 2Na2SO4 ○ 4 Identification of SO3 2- SO3 2- + 2H+ = H2SO3→ SO2 ↑+ H2O The test paper of fuchsine: red → colorless 2. Sulfuric acid and sulfates