Oxidation RulesNeutral Compound = 0 (NO -) | Ion= ion charge (w/ -) | +1 w/ non-metals (Hydrogen) | Oxygen usually -2, -1 in peroxide (H2O2) | -1 w/ metals (H) | Group 1A: always +1 | Halogens: usually -1, positive w/ oxygen | Group 2A: always +2 | F always -1 | Monatomic Ions: made with one atom, same as their charges | EXAMPLE: |
| | Redox EquationsReduction: gain of electrons | Oxidation: loss of electrons | e-: electron | OIL: oxidation is loss (of electrons) | RIG: reduction is gain (of electrons) | OIL as half reaction: Na > Na(+) + e- | RIG as half reaction: Cl + e- > Cl- | for oxidation: e- on right | for reduction: e- is on left | If OX # ^ it is OIL | EXAMPLE: | If OX # goes down it is RIG |
BatteriesDefinition: a series of voltaic cells that produces a voltage that is the sum of the voltages of the individual cells | Types | Dry Cell Battery: Typical AA, AAA, C, & D | Lead Storage: 12 V (6 cells that each provide 2V) | Anode: Zinc, Cathode: graphite, all immersed in KOH | Anode: Lead, Cathode: PbO2, all immersed in sulfiric acid | Advantage: cheap and small | must be recycled! | Disadvantage: not recharagable | to keep electrodes from touching, wood or glass fiber spacers are used | Recharagable Batteris: includes lithium ion, nickel-cadmium, and nickel metal hydride batteries | Voltage may vary as the H2SO4 is used, even after recharging | Built in or separate charger | Advantage: large voltage, can be recharged | Advantage: rechargable | Disadvantage: heavy, expensive, takes up a lot of space | Disadvantage: cost | Fuel Cells: 2H2(g) + O2 (g) > 2H2O(I) | | | Hydrogen is oxidized, electrons used to create electricity | | | Used in spacecraft, too $$ for general use | | | Adv: no recharge, only emission is water | | | Dis: cost |
| | Calcuating Cell PotentialFind correct half reactions on green sheet | Down reduction potential, oxidation more likely (more positive voltage) | Write down half reactions on paper along with voltage | higher voltage is e red, flip other half reaction to make oxidation and change sign given on green sheet (write it backwards) | Add the half reactions and voltages together (e- should cancel) |
| | Writing Half ReactionsAssign oxidation numbers | Ex: Zn + Cu2+ > Zn2+ + Cu | Put the atoms with changing oxidation numbers in a separate reaction | Balance all atoms | Balance charge by adding e- to more positive side |
Voltaic CellCathode: site of reduction (gaining e-) | Neutral atoms make solid metal | Anode: sire of oxidation (losing e-) | Metal ions can usually dissolve in water | Definition: devices that use a chemical reaction to create electricity | Cell Notation/Diagram: two half reactions combined | | | Ex: Zn(s)|Zn2+(aq)||Cu2+(aq)|Cu(s) |
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