lecture 243/14/06. balancing redox reactions h 2 c 2 o 4 (aq) + mno 4 - mn 2+ + co 2 (g) oxalic...
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Lecture 24 3/14/06
Balancing Redox reactions
H2C2O4 (aq) + MnO4- Mn2+ + CO2 (g)
oxalic acid permanganate
1. Break into half-reactions2. Balance the atoms3. Combine the half-reactions4. Check for mass and charge balance
Redox example: respiration/combustion
Balance redox reaction for glucose (C6H12O6) respiration (same as combustion reaction)
How do the oxidation numbers of carbon and oxygen change?
What is being oxidized? What is being reduced?
What is the oxidizing agent? The reducing agent?
Acid Mine Drainage
FeS2 (pyrite)
www.state.sd.us/denr/DES/mining/P000106.jpg
http://www.nelpi.org/tarcreek/slides/5s.html
Redox under basic conditions:
Balance the following redox reaction in a basic solution
CrO42- + SO3
2- Cr(OH)3 + SO42-
Displacement reactions
Some metals react with acids to produce salts and H2 gas
Balance the following displacement reaction:
Zn (s) + HBr (aq) ZnBr2 (aq) + H2 (g)
Apparatus with oxidation and reduction Apparatus with oxidation and reduction reactions in different compartmentsreactions in different compartments redox reaction occurs by transferring electrons redox reaction occurs by transferring electrons
through an external connectorthrough an external connector
voltaic or galvanic cell product favored reactionproduct favored reaction produces electric current produces electric current
electrolytic cell reactant favored reactionreactant favored reaction external electric current used to drive reactionexternal electric current used to drive reaction
Electrochemical cells
Voltaic (Galvanic) Cells
Redox reaction must favor products
Electrodes Anode: where oxidation occurs Cathode: where reduction occurs
Salt bridge Need salt bridge or porous barrier in order to
maintain charge balance in each compartment
External circuit Wire to allow electrons to flow between electrodes