CHEM 1E03 Lecture Notes - Lecture 20: Bromine Monochloride, Phenolphthalein, Redox Indicator

• School: McMaster University
• Department: Chemistry
• Course: CHEM 1E03
• Professor: Randall Dumont; Linda Davis

Document Summary

Example basic: mno4- + i- mno2 + i2. Oxidation numbers in order: +7, -2, -1, +4, -2, 0. Addition of h+: leave alone add 2 water molecules so each side 4o. 4h+ + mno4- + 3e- mno2 + 2h20. Equalizing h+ with oh-: leave alone leave alone. 4oh- + 4h+ + mno4- + 3e- mno2 + 2h20+ 4oh- 4h2o + mno4- + 3e- mno2 + 2h20+ 4oh- 2h2o + mno4- + 3e- mno2 + 4oh- Therefore by cancellation: 6i- + 4h2o + 2mno4 3i2 + 2mno2 + 8oh- Example acidic: h2o2 + al h2o + al3+ Oxidation numbers in order: +1, -1, 0, +1, -2, -3. [2h2o + mno4- + 3e- mno2 + 4oh-] * 2. [4h2o + 2mno4- + 6e- 2mno2 + 8oh-] H2o2 + 2e- 2 h2o (no h involved in this reaction leave alone leave alone (both sides have the same #h) Therefore by cancellation: 2al + 3h2o2 2 al3+ + 6h2o.