Download Chemistry Exam 3: Fuel Cells, Solar Energy, and Water Quality - Prof. Charles Sharpless and more Exams Chemistry in PDF only on Docsity! November 30th, 2007 Chemistry 331 50 minutes Exam 3 KEY N ame __________________________________________ Part A: Short answer, 6 points each. Be brief! 1) Cathode ½ reactions for different fuel cells are shown below. Identify the fuel cell type. ½ O2 + 2e- O2- Solid Oxide Fuel Cell ½ O2 + 2e- + CO2 CO32- Molten Carbonate Fuel Cell ½ O2 + 2e- + H2O 2OH- Alkaline Fuel Cell ½ O2 + 2e- + 2H+ H2O Polymer Electrolyte or Phosphoric Acid FC 2) Match Terms on the Left with Descriptions on the Right. Fusion Heating water by sunlight & circulating to warm a house - + + + + + + + + + + + + + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -+ Heating fluid by sunlight, using fluid to boil water, make steam, and drive a turbine Fission Reaction of two nuclei to form one nucleus Heating by direct sunlight Solar Thermal Power Separation of 235U from 238U neutron capture by Cd Passive Solar Reaction of one nucleus to form two nuclei 3) Shown below is a picture from a lecture slide. What device does the picture depict? A semiconductor n-p junction A What is region “A” called? The charge depletion region What has occurred in region A? h+ from the p-type layer have joined with e- from the n-type layer Briefly state how sunlight can cause this device to generate electricity. Sunlight energy can break apart the e-/h+ pairs to create an electrical current. -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 lo gC 3 4 5 6 7 8 9 10 pH Al3+ AlOH2+ Al(OH)2+ Al(OH)30 Al(OH)4- AlTOT 4) Match the points in the solubility diagram to the correct description. Solid is present Point C Solid could form by increasing pH Point A Solid could form by decreasing pH Point B Solid cannot form by adjusting pH Point D C A B D 5) True or False. When phytoplankton grows, it consumes O2 T F Biochemical O2 demand is usually greater than chemical O2 demand T F In the process of nitrogen fixation, N2 is converted to NH3 or organic N T F Phosphates are more soluble than nitrates, so they wash away faster T F When O2 is depleted, bacteria will turn to sulfate for energy, then nitrate T F 6) When groundwater is contaminated, monitoring wells are used to follow the concentration of the flowing contaminants. In the space given below, sketch two curves illustrating the concentration vs time profile for (a) a contaminant that doesn’t bind to soil, and (b) a contaminant that binds to soil. Using points from these curves, finish the equation that defines the retardation factor. R = __________ 7) What does TSCA stand for? What is significant about this piece of legislation? Toxic Substances Control Act. This legislation directs EPA to assess the public health risk of industrial chemicals. This is a very large job, requiring a lot of environmental fate data, and it has been a major driver in the push for fate estimation tools. Time Concentration (unretained, peak at t0) (retained, peak at tr) tr / t0
