ng d n gi i t p Hóa phân tích - Khoa Cơng Ngh Hóa H c 6.1 - electron Fe2+ + MnO4- + H+ Fe3+ + Mn2+ + H2O C2O42- + MnO4- + H+ Mn2+ + H2O + CO2 H2O2 +MnO4- + H+ Mn2+ + H2O + 5O2 NO2- +MnO4- + H+ Mn2+ + H2O +NO3- Cr2O72- + I- + H+ Fe3+ + II3- + S2O32a Fe2+ + MnO4- + H+ Fe2+ - 1e Cr3+ + I3- + H2O I3- + Fe2+ I- + S4O62 Fe3+ + Mn2+ + H2O Fe3+ MnO4- + 8H+ + 5e x5 Mn2+ + 4H2O x 5Fe2+ + MnO4- + 8H+ b C2O42- + MnO4- + H+ MnO4- + 8H+ + 5e C2O42- -2e 5Fe3+ + Mn2+ + 4H2O Mn2+ + H2O + CO2 Mn2+ + 4H2O x 2 CO2 5C2O42- + 2MnO4- + 16H+ c H2O2 +MnO4- + H+ MnO4- + 8H+ + 5e H2O2 - 2e x5 2Mn2+ + 8H2O + 10CO2 Mn2+ + H2O + 5O2 Mn2+ + 4H2 + ) +) O2 + + Sau 5H2O2 +2MnO4- + 6H+ + 2Mn2+ + 8H2O + 5O2 + x5 x2 ng d n gi i t p Hóa phân tích - Khoa Cơng Ngh Hóa H c d NO2- +MnO4- + H+ Mn2+ + H2O +NO3- MnO4- + 5e NO2- Mn2+ x2 NO3- -2e 2MnO4- + 5NO2- x5 2Mn2+ + 5NO3 + 2MnO4- + 5NO2- + 6H+ 2Mn2+ + 5NO3+ 3H2O e Cr2O72- + I- + H+ Cr3+ + I3- + H2O Cr2O72- + 6e + 14H+ 2I- -2e I2 + I Cr3+ + 7H2O - 3I- - - x3 Cr2O72- + 9I- + 14H+ f Fe3+ + I- Fe3+ 2Cr3+ + 3I3- + 7H2O I3- + Fe2+ 3I- - 2+ I3- + Fe2+ g I3- + S2O323I- 2S2O32- + 2e x1 x2 2Fe3+ + 3I- I- + S4O623 x1 S4O62 x I3- + S2O32- I- + S4O62 6.2 a.CrO2- , H2O/Cr, OHb.SO42-,H+/H2SO3, H2O c.AsO43-,H+/AsO33-,H2O a CrO2- + 3e + 2H2O x1 - ng d n gi i t p Hóa phân tích - Khoa Cơng Ngh Hóa H c b, SO42- + 2e + H2SO3 (thi u 2H+ th a 1oxy) SO42- + 2e + 4H+ H2SO3 + H2O c AsO43-,H+/AsO33-,H2O AsO43- + 2e + 2H+ AsO33- + H2O 6.4 I2/I-)=0,54V AsO 34 + 2I- + 2H+ AsO 34 + 2e + 2H+ 2I- - 2e (H3AsO4/ H3AsO3)= 0,559 V: E0( AsO 33 + I2 + H2O AsO 33 + H2O I2 AsO 34 / AsO 33 E = Eo + lg [H+]2 + ] lg ] hi: [AsO 34 ] = [AsO 33 ] = 1(M) [H+]= 100 (M) Khi pH=8 dktc E0 (H3AsO4/ H3AsO3)= 0,559 V > E0( I2/I-)=0,54V E = Eo + o lg [H+]2 + lg ] ] khi: [AsO 34 ] = [AsO 33 ] = 1(M) [H+]= 10-8 (M) Eo'= Eo y pH = 0,57 0,059 × = 0,098V pH =8 , [AsO 34 ] = [AsO 33 ] = 1(M) o =0.098v < E0( I2/I-)=0,54V Nên I2 AsO 33 Ph n ng s x y theo chi 6.5 Ag+/Ag 0,8 c ng d n gi i t p Hóa phân tích - Khoa Cơng Ngh Hóa H c Ag+/Ag Cl+ + 1e Ag (1) - Ag+ + Cl- AgCl Ag + Cl- 1e (2) Trong du {AgCl / Ag, Cl- } th chu + u ki n c a c p - Ag /Ag có m t Cl => - 6.7 4 - 2+ MnO4- + 5e- + 8H+ không màu Mn2+ + 4H2O MnO4=MMnO4/5 - - MnO4 + 3e + 4H + MnO2 + 2H2O MnO4- + 3e- + 2H2O MnO2 - MnO4- + 1e- MnO4=MMnO4/3 - Trong 6.8 24 MnO4=MMnO4/1 ng d n gi i t p Hóa phân tích - Khoa Cơng Ngh Hóa H c KMnO4 KMnO4 4 4 : KMnO4 + H2O = MnO2 + 4KOH + 3O2 (1) KMnO4 trình (1) 6.9 4 1N 4 - (VN) = (VN)s 6.10 2C2O4.2H2 6.11 2C2O4 2SO4 2SO4 2SO4 2SO4 VNM/10ZPd (Z=2)=326ml ng d n gi i t p Hóa phân tích - Khoa Cơng Ngh Hóa H c 325ml H2SO4 - 1l 6.12 2C2O4 0,05N thêm vào 5ml H2SO4 4 theo Fe NKmnO4 = (NV)H2C2O4 /VKmnO4 =0.0515N 2+ 5Fe2+ + MnO4- + 8H+ TKNMnO4/Fe = NKmnO4 Fe/1000 5Fe3+ + Mn2+ + 4H2O = 2.8896 /1000 = 2.9 mg/l 6.13 2C2O4 2O2 5Fe2+ + MnO4- + 8H+ 5Fe3+ + Mn2+ + 4H2O 5C2O42- + 2MnO4- + 16H+ 2Mn2+ + 8H2O + 10CO2 5H2O2 + 2MnO4- + 6H+ 2Mn2+ + 8H2O + 5O2 6.14 H2SO4 4 0,1000N? 3+ Fe + H2SO4 = FeSO4 + H2 ) 5Fe2+ + MnO4- + 8H+ 5Fe3+ + Mn2+ + 4H2O Fe x (NV)KmnO4 x 100]: mmau = [56 x 10-3 x (24.85 x 0.1) x 100 ]/0.14 =99.4% 6.15 2O3 30 ml KMnO4 0,1N ng d n gi i t p Hóa phân tích - Khoa Cơng Ngh Hóa H c Fe2+ Fe2O3 KMnO4 KmnO4 2O3 x 10-3 x Mfe KmnO4 x 10-3 x Mfe x (MFe2O3/2MFe) KmnO4 x 10-3 x (MFe2O3/2) x(100/a) (a : %Fe2O3 có VKmnO4=20ml mquang = 0.2286g VKmnO4=30ml mquang = 0.3429g 6.16 H2SO4 2C2O4 2C2O4 C2O42- + MnO2+ 4H+ Mn2+ + 2H2O + 2CO2 5C2O42- + 2MnO4- + 16H+ 2Mn2+ + 8H2O + 10CO2 - H2C2O4 NH2C2O4 = 0.036N - 2C2O4 MnO2 x [(NV)H2C2O4 (NV)MnO4] (MMn x10-3/2) x [(NV)H2C2O4 (NV)MnO4] - % Mn = (MMn x10-3/2) x [(NV)H2C2O4 (NV)MnO4]x 100/mmau = 6,875% 6.17 2C2O4 CaC2O4 C2O42- + Ca2+ = CaC2O4 Tách k t t a chu n H2C2O4 5C2O42- + 2MnO4- + 16H+ K thu t chu 2Mn2+ + 8H2O + 10CO2 c: mCa+ = (MCa x10-3/2) x [(NV)H2C2O4 (NV)MnO4] x (250/25) = 0.74g 6.18 2C2O4 ng d n gi i t p Hóa phân tích - Khoa Cơng Ngh Hóa H c I2, I2 6.19 Na2S2O3 KI3 2Cr2O7 25ml? Cách 1: cân m g K2Cr2O7 , V =200ml Vxd =10ml Na 2s2o3 =25 gam K2Cr2O7 có m g K2Cr2O7 : mK2Cr2O7 N ng K2Cr2O7 ng dung d ch K2Cr2O7 (mK2Cr2O7 K2Cr2O7)* nh lu (mK2Cr2O7 (1000/200) ng K2Cr2O7)* (1000/200) * (10) = 25 * 0.1 mK2Cr2O7 Cách 2: Có th công th c mK2Cr2O7 = mDK2Cr2O7 * (NV)Na2S2O3 * (Vdm/Vxd) V i Vdm = 200ml Vxd= 10ml 6.20 thiosunfat 0,1100N? Cl2 + KI = I2 + KCl I2 + Na2S2O3 = 2NaI + Na2S2O3 mCl2 = mDCl2 * ((NV)Na2S2O3 * (1000/25) = 3,139g ... KMnO4 trình (1) 6. 9 4 1N 4 - (VN) = (VN)s 6. 10 2C2O4.2H2 6. 11 2C2O4 2SO4 2SO4 2SO4 2SO4 VNM/10ZPd (Z=2)=326ml ng d n gi i t p Hóa phân tích - Khoa Cơng Ngh Hóa H c 325ml H2SO4 - 1l 6. 12 2C2O4 0,05N... Mn2+ + 4H2O = 2.88 96 /1000 = 2.9 mg/l 6. 13 2C2O4 2O2 5Fe2+ + MnO4- + 8H+ 5Fe3+ + Mn2+ + 4H2O 5C2O42- + 2MnO4- + 16H+ 2Mn2+ + 8H2O + 10CO2 5H2O2 + 2MnO4- + 6H+ 2Mn2+ + 8H2O + 5O2 6. 14 H2SO4 4 0,1000N?... VKmnO4=20ml mquang = 0.2286g VKmnO4=30ml mquang = 0.3429g 6. 16 H2SO4 2C2O4 2C2O4 C2O42- + MnO2+ 4H+ Mn2+ + 2H2O + 2CO2 5C2O42- + 2MnO4- + 16H+ 2Mn2+ + 8H2O + 10CO2 - H2C2O4 NH2C2O4 = 0.036N - 2C2O4 MnO2