CHEM/GEOL 140 Final Exam (Due next Tues, May, 5th, 12 pm) CHEM/GEOL 3140 1. Balance the following redox reaction (8 points): CH4 + UO2CO3o ( UO2 + HCO3- FeS2 + NO3- ( SO42- + Fe(OH)3 + NO2- 2. You...

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CHEM/GEOL 140 Final Exam (Due next Tues, May, 5th, 12 pm) CHEM/GEOL 3140 1. Balance the following redox reaction (8 points): CH4 + UO2CO3o ( UO2 + HCO3- FeS2 + NO3- ( SO42- + Fe(OH)3 + NO2- 2. You made a 10-4 M NaOH solution in distilled water. You measured and recorded the pH of the solution and then went on for a long trip (assuming the solution was open air but no evaporation occurred while you were gone). You measured the pH again upon your return but got a different reading. (1) What were the pH readings before and after the trip? (15 points) (2) What had happened while you were away? (2 points) 3. A water contains 10-3 M NO3-, and equal amount of HCO3- and CH4 (aq). Assuming NO3- is in equilibrium with atmospheric N2 (0.8 atm), what is the Eh of this water? Using data in Appendix B if needed (15 points). 4. An acid mine drainage water containing 10-5 mol/L Fe2+ is neutralized to pH 6. Measured final Eh value of the water is 0.2 V and assumed to be constant (ref. to the stability diagram of Fe2+-Fe3+-Fe(OH)2-Fe(OH)3-H2O system). a. Derive the relation showing how ferrous iron concentration responds to pH increase in the neutralization process. (5 points) b. Please determine the final concentration of the ferrous iron? (10 points) 5. The concentration of Mg2+ in seawater is 10-1.87 M, at what pH would seawater, amorphous SiO2(a) (K = 2x10-3), and sepiolite [Mg4Si6O15(OH)2(6H2O] all be in equilibrium? Use the thermodynamic data in the textbook. (15 points) 6. A fluid (water) inclusion found in a calcite crystal has a δD value of -175‰. The measured δ18O value of the calcite is +10‰. Estimate the temperature (oC) when the calcite was formed. Assume the water was of meteoric origin and isotopic equilibrium was established between the enclosed water and the calcite crystal. Use the following paleothermometer: 103ln calcite water a = 2.78x106/T2 – 2.89 (Hint: find the fractionation factor of O between water and calcite using the known δD and δ18O values) (15 points). 7. Construct the topologic diagram for the stability field of analcite NaAlSi2O6(H2O in water at 25 oC. Assuming transformation occurs between analcite, kaolinite, gibbsite, and beidelite [Na0.33(Al2.33Si3.67)O10(OH)2]. Show your work (15 points). _1302595501.unknown