The water in a sewer is at pH 8.20, has an ALK of 2.50 meq/L, and contains 2.25 mmol/L TOTCO3. All the alkalinity is con

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The water in a sewer is at pH 8.20, has an ALK of 2.50 meq/L,
and contains 2.25 mmol/L TOTCO3. All the
alkalinity is contributed by species in the carbonate and sulfide
acid/base groups. (a) What would the partial pressures of
CO2 and H2S be in a gas phase that has
equilibrated with the solution?
(b) What is TOTH in the solution, if H+ ,
HCO-3 and HS− are chosen as
components?
(c) As the water enters a sewage treatment plant, it is dosed
with HOCl, converting all the sulfide species to sulfate. The
reactions of H2S and HS− with HOCl are
H2S + 4 HOCl --->
SO42- + 4Cl- + 6
H+
HS- + 4 HOCl --->
SO42- + 4Cl- + 5
H+
If the HOCl dose is just enough to react with all the
TOTS(II), what will TOTH be before any
re-equilibration with the gas phase occurs? Use the same components
as in part (b), along with Cl− and
SO42− .