Balance an oxidation-reduction equation in a basic medium from the ones covered in the lecture notes currently available
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- Balance An Oxidation Reduction Equation In A Basic Medium From The Ones Covered In The Lecture Notes Currently Available 1 (30.65 KiB) Viewed 10 times
- Balance An Oxidation Reduction Equation In A Basic Medium From The Ones Covered In The Lecture Notes Currently Available 2 (102.52 KiB) Viewed 10 times
4.10 Balancing Oxidation-Reduction Equations I. Acidic Medium MnO4 + Fe+2 → Fe+3 + Mn+2 1. Write separate equations for the oxidation and reduction half reactions MnO→ Mn+2 reduction half-reaction Fe+2 → Fe+3 oxidation half-reaction 2. For each half reaction a. Balance all elements except hydrogen and oxygen. b. Balance oxygen using H,0. c. Balance hydrogen using H+. d. Balance the charge using electrons. 5e + 8H+ + MnO4 → Mn+2 + 4H2O Fe+2 → Fe+3 + le 3. Equalize the electron transfer in the two half reactions. 5Fe+2 → 5Fe+3 + 5e- 4. Add the half reactions 5e* + 8H+ + MnO, + 5Fe+2 → Mn+2 + 4H20 + 5Fe+3 + 5e* 5. Check that elements and charges are balanced 5Fe, 8H, 1Mn, 40 = 5Fe, 8H, 40, 1Mn +8 -1 +10 +2 +15 =
II. Basic Medium 1. Use the half-reaction method as specified for acidic solution. Ag + CN: + 02 → Ag(CN)2 4Ag + 8CN- + O2 + 4H+ + 4e + 4Ag(CN)2 + 4e + 2H20 4Ag + 8CN: + O2 + 4H+ + 4Ag(CN)2 + 2H20 2. Add OH- to both sides of balanced equation to eliminate H+ ions. 40H+ + 4Ag + 8CN- + O2 + 4H+ + 4Ag(CN), + 2H20 + 40H- 4Ag + 8CN- + O2 + 4H20 + 4Ag(CN)2 + 2H,0 + 40H- 3. Eliminate as many H,0 molecules as possible. 4Ag + 8CN- + O2 + 2H20 + 4Ag(CN)2 + 40H 4. Check that elements and charges are balanced. 4Ag, 8CN, 40, 4H = 4Ag, 8CN, 40, 4H 0-8 = -4-4