The acid sulfite pulping process uses sulfurous acid (H2SO3) to attack the lignin that holds the wood fibers together. The fibers are then released and processed into paper products, and a hot solution containing acetic acid, sulfurous acid, and some larger organic molecules is generated as a waste. This waste solution is partially evaporated and then condensed, with the smaller molecules being transferred into the evaporator condensate and the larger ones remaining behind in an organic-rich solution that can be burned to recover its energy content. The condensate can be treated in an anaerobic biological treatment process, but only if the pH is maintained near neutrality (pH 7). When the process is operating successfully, the microorganisms mediate the following reactions (CH4 is methane)

CH3COOH + H2O CH4 + H2CO3 4 H2SO3 + 3 CH3COOH 4 H2S + 6 H2CO3

(Note: neglect the possible formation of the species S2O52-, which can form from the combination of two HSO3- ions and release of a water molecule.) Also note that the solution is likely very acidic and the solution will be dominated by one acid from above. (a) Find the pH of a solution of 5000 mg/L HAc and 300 mg/L H2SO3-S. (b) What would the solution pH be if all the HAc and all the H2SO3 were destroyed according to the above reactions, and if all the H2CO3 that was generated remained in solution? CH4 undergoes no acid/base reactions. (In reality, much of the H2CO3 dehydrates to CO2, which then forms bubbles along with the CH4 and exits the solution.)