Transcript Slide 1
Balancing Redox Reactions I2 (s) + Al (s) AlI3 MnO4- + C2O42- Mn2+ + CO2 MnO4- + C2O42- Mn2+ + 2 CO2 2 O2 HELP 4 H2O 4 OH- MnO4- + C2O42- Mn2+ + CO2 1. Break it into two half-reactions MnO4- Mn2+ C2O42- CO2 2. Balance redox active species MnO4- Mn2+ 3. Balance oxygen using H2O MnO4- Mn2+ + 4 H2O +7 +2 MnO4- Mn2+ 4. Balance hydrogen using H+ 8 H+ + MnO4- Mn2+ + 4 H2O 5. Balance charge using e5 e- + 8 H+ + MnO4- Mn2+ + 4 H2O This is a balanced half-reaction electrons are a ________ reactant MnO4- is _______ gaining electrons MnO4- is being _______ reduced Where do the e- come from? C2O42- CO2 2. Balance redox active species C2O42- 2 CO2 3. Balance oxygen using H2O C2O42- 2 CO2 4. Balance hydrogen using H+ C2O42- 2 CO2 5. Balance charge using eC2O42- 2 CO2 + 2e- +3 +4 C2O42- 2 CO2 + 2eThis is a balanced half-reaction electrons are a ________ product C2O42- is _______ losing electrons C2O42- is being _______ oxidized Now combine the two half-reactions 2 ( 5 e- + 8 H+ + MnO4- Mn2+ + 4 H2O ) 5 ( C2O42- 2 CO2 + 2e- ) 16H+ + 2MnO4- + 5C2O42- 2Mn2+ + 8H2O + 10CO2 stoichiometry additional product, H2O additional reactant, acid Ag+ (aq) + C6H12O6 (aq) Ag (s) + C6H12O7 (aq) Ag+ Ag (s) C6H12O6 C6H12O7 Ag+ + C6H12O6 Ag (s) + C6H12O7 balance mass Ag+ + e- Ag (s) balance oxygen H2O balance hydrogen H+ balance charge e- H2O + C6H12O6 balance mass balance oxygen H2O balance hydrogen H+ balance charge e- C6H12O7 + 2 H+ + 2 e- H2O + C6H12O6 C6H12O7 + 2 H+ + 2 e- 2 ( Ag+ + e- Ag (s) ) H2O + C6H12O6+ 2Ag+ C6H12O7+ 2 H+ + 2Ag (s) Ag+ reduced Ag+ oxidizing agent C6H12O6 oxidized C6H12O6 reducing agent C C H2O + C6H12O6 C6H12O7 + 2 H+ + 2 e- 2 ( Ag+ + e- Ag (s) ) H2O + C6H12O6+ 2Ag+ C6H12O7 +2 H+ + 2Ag (s) 2 OH2 OH2 H2O This reaction takes place in a basic solution OH1 + 2OH +H2O+C6H12O6+2Ag C6H12O7 +2Ag (s)+2 H2O 2OH- + C6H12O6 +2Ag+ C6H12O7 +2Ag (s) + H2O CN-(aq) + MnO4- (aq) CNO- (aq) + MnO2 (s) separate half-reactions CN- CNO- MnO4- MnO2 balance mass CN- CNO- MnO4- MnO2 balance oxygen CN- CNO- MnO4- MnO2 CN- CNO- MnO4- MnO2 balance hydrogen CN- CNObalance charge MnO4- MnO2 make the solutions basic add OH-