The zinc-air battery shows much promise for electric cars because it is lightweight and rechargeable: The net transformation is Zn(s)11 2O2(g) SZnO(s). (a) Write the half-reactions at the zinc-air electrodes and calculate the standard emf of the battery at 25C. (b) Calculate the emf under actual operating conditions when the partial pressure of oxygen is 0.21 atm. (c) What is the energy density (measured as the energy in kilojoules that can be obtained from 1 kg of the metal) of the zinc electrode? (d) If a current of 2.1 3 105 A is to be drawn from a zinc-air battery system, what volume of air (in liters) would need to be supplied to the battery every second? Assume that the temperature is 25C and the partial pressure of oxygen is 0.21 atm.
Week 2: • Activity along mid-ocean ridges: o Deep ocean environments exist where ridges of tectonic plates exist § Newly made rock continuously being regenerated from magma underneath, solidified immediately by cold water § Geologic, seismic environments § “Chimneys” of rock form and release heat, smoke, toxic materials, etc. o Abundant oasis of life along black smokers: huge temperature gradient § How does life survive within such a temperature gradient • The sea floor: summary o Earth exists as layers with differe nt densities and temperatures: § Core, mantle, crust (continental vs. oceanic) o Distribution of land masses and water masses has not always been what it is today § Theory of continental drift versus mechanism of plate tectonics § Lithospheric plates, ridges, trenches, subduction zones, o Sea floor: § Continental margins (active vs. passive) § Continental shelf, slope, rise and abyssal plain § Lithogenous sediments, biogenous sediments, abyssal clay Unit 2: Chemical and Physical features of seawater and the world oceans • Learning objectives: o Basic