Balancing Oxidation-Reduction Reactions in Acidic & Basic Solutions Chapter 4.10 Balancing Oxidation-Reduction Reactions in Acidic & Basic Solutions

Balancing Oxidation-Reduction Equations Half-Reaction Method: Separate the full equation into 2 half-reactions (oxidation and reduction) Balance each half-reaction separately Add them together to get full balanced equation

Balancing in ACIDIC solution 1. Write separate equations for the oxidation and reduction half-reactions 2. For each half-reaction: Balance all elements BUT H and O Balance O using H2O Balance H using H+ Balance charge using electrons (e-) 3. If necessary, multiply one or both half-reactions to ensure equal numbers of electrons transferred in the two half-reactions 4. Add half-reactions together & cancel identical species 5. Check to make sure elements and charges are balanced

MnO4- (aq) + Fe+2(aq) Fe+3(aq) + Mn+2(aq) Balance the following redox reaction in acidic solution: MnO4- (aq) + Fe+2(aq) Fe+3(aq) + Mn+2(aq) 1. Write the separate half-reactions 2. Balance each half-reaction

3. Equalize the electron transfer in the two half-reactions 4. Add the two half-reactions and cancel identical species

Balance the following redox reaction in acidic solution: H+(aq) + Cr2O7-2(aq) + C2H5OH(l) Cr+3(aq) + CO2(g) +H2O(l) 1. Write the separate half-reactions 2. Balance each half-reaction

3. Equalize the electron transfer in the two half-reactions 4. Add the two half-reactions and cancel identical species

Balancing redox reactions in BASIC solution 1. Balance using acidic method 2. Add OH- ions to both sides, equal to #H+ ions 3. Form water on the side of equation that contains both ions 4. Simplify # water molecules 5. Check balancing

Balance in BASIC solution: Ag(s) + CN-(aq) + O2(g) Ag(CN)2-(aq) 1. Write the separate half-reactions 2. Balance each half-reaction

3. Equalize the electron transfer in the two half-reactions 4. Add the two half-reactions and cancel identical species

5. Add OH- ions to both sides of the equation to equal the # of H+ 6. Form water on the side contain both ions (H+ and OH-) & simplify H2O molecules

PRACTICE...PRACTICE...PRACTICE !