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