Cr203+3KS,0,-> Cr2(SO4)3+3 K2SO4 4. Thiosulfuric acid and thiosulfates 1) Thiosulfuric acid: Thermal instability:H2S2O3→SO2↑+S↓+H2O 2) Thiosulfates Na2S2O3. 5H2O: sodium thiosulfate, hypo JPreparation: Na2SO,+S>Na2S203 6 is stable in neutral or basic medium, if we add acid to solution, the following reaction wIll occur 02+2Ht=H2S2O3→SO2↑+S+H2O 3 Reducing properties S2O32+12=S4O2+2I S203+4Cl2+5H20=2S04+8CI+10H SAgCl+2S203=LAg(S2O3)2]+CI AgBr+2S203=Ag(S2O3)]+Br Identification Add acid:S2O32+2H→SO2↑+S↓+H2O Add AgNO3: 2Ag+S2O3-Ag2S2O31 Ag2S2O3+H2o-Ag2SI+H2SO4 White-yellow-orange-brown-black 5. Persulfuric acid and persulfates 1)Persulfuric acid Structure Preparation: electrolyze NH4HSO4 Anode: 2SO4-2e= S2O8 Cathode: 2H+ 2e= H2 2HSOA electroly s,0 -+H 2)Persulfates 第20页 2006-02-22第 20 页 2006-02-22 20 Cr2O3+3K2S2O7 →Δ Cr2(SO4)3+3 K2SO4 4. Thiosulfuric acid and thiosulfates 1) Thiosulfuric acid: Thermal instability: H2S2O3→SO2↑+S↓+H2O 2) Thiosulfates: Na2S2O3·5H2O: sodium thiosulfate, hypo ○ 1Preparation: Na2SO3 + S →Δ Na2S2O3 ○ 2 S2O3 2- is stable in neutral or basic medium, if we add acid to solution, the following reaction will occur: S2O3 2-+ 2H+ =H2S2O3→SO2↑+S↓+H2O ○ 3 Reducing properties S2O3 2- + I2 = S4O6 2- + 2I￾S2O3 2-+4Cl2+5H2O=2SO4 2-+8Cl- +10H+ ○ 4AgCl+2S2O3 2-=[Ag(S2O3)2] 3-+Cl￾AgBr+2S2O3 2-=[Ag(S2O3)2] 3-+Br- ○ 5Identification Add acid: S2O3 2-+ 2H+ →SO2↑+S↓+H2O Add AgNO3: 2Ag+ +S2O3 2-→Ag2S2O3↓ Ag2S2O3+H2O→Ag2S↓+H2SO4 White-yellow-orange-brown-black 5. Persulfuric acid and persulfates 1) Persulfuric acid ○ 1Structure ○ 2Preparation: electrolyze NH4HSO4 Anode: 2SO4 2- - 2e = S2O8 2- Cathode: 2H+ + 2e = H2 2HSO4 - S2O8 2- + H2 2) Persulfates electroly