concentration cell - cell based on emf generated from difference in concentration

• uses same substance
• will operate until concentration equal
• use Nernst equation to figure out
• emf of voltaic cell decreases as it discharges

battery - portable, self-contained electrochemical power source w/ 1 or more voltaic cells

• use multiple voltaic cells >> greater voltage
• primary cells - can’t be recharged
• secondary cells - can be recharged from external power source
• lead-acid battery - 2V battery w/ lead dioxide as cathode and lead anode
  • 6 strung together in 12-V automotive battery
  • can be recharged
• alkaline battery - most common primary battery
  • manganese oxide and graphite mixed in cathode, zinc anode
  • emf of 1.55
• nickel-cadmium (nicad) battery - most common rechargeable battery
  • environmental hazard, increases weight of batteries
• nickel-metal-hydride (NiMH) battery - uses alloy for anode
• litium-ion (Li-ion) battery - has higher energy density than nickel-based batteries
• fuel cells - uses conventional fuels, not batteries (not self-contained)
  • most promising system uses hydrogen/oxygen, forms water as only product

corrosion - metal converted to unwanted compound due to environment

• rusting - forms Fe2O3 * xH2O from iron/oxygen
  • rust usually deposits at cathode (largest supply of oxygen)
• paint/metal coatings added to protect against corrosion
• galvanized iron - zinc layer added on to iron
  • zinc gets corroded before iron
  • sacrificial anode - oxidized first to protect another cathode

electrolysis - nonspontaneous redox reactions started by outside energy source

• electrolytic cell made of 2 electrodes in molten salt or solution
• electrolysis of molten salts needs high temperatures
• inert electrodes - serve as surface where oxidation/reduction occur
• active electrodes - participate in oxidation/reduction process
• electroplating - uses electrolysis to deposit thin metallic layer on another metal