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
Subject:
Subject X2:
