The microorganisms in a waste treatment pond are exposed to 35 mg/L of easily degradable organic compounds with a typical composition C5H10O5. The standard molar Gibbs energy of formation of these compounds is -2797 kJ/mol. The pond is at pH 7.3, its temperature is 25ºC, and its alkalinity is 2 x 10-3 eq/L. The overall reaction for the organic matter is:
C5H10O5+ 5O2(aq) ? 5H2CO3(aq)
a. Due to oxygen consumption by the above reaction, the dissolved oxygen concentration in the water is only 2 mg/L. What is the maximum amount of energy that an organism could obtain by oxidizing 1 µmol of the organic matter?
b. The operator of the treatment facility has suggested that the treatment efficiency could be improved by bubbling air through the water to encourage biological activity. Would the organisms find the environment in the untreated water more favourable, less favourable, or identical (from an energy standpoint) after equilibration with air? Explain briefly - a calculation wouldn't hurt to make your point.
c. Determine the pH of the system after it has been bubbled with air.