A plant manufacturing nails and screws uses a large pool (volume = 10,000 L) to collect and treat its residual waste water before discharging it in a nearby stream. The manufacturing process makes use of a strong acid (HCl) and a weaker one (phosphoric acid, H3PO4; pKa1 = 2.148, pKa2 = 7.20, pKa3 = 12.15), before discharging them in the pool for treatment (neutralization). Once the pool is filled to its maximum capacity, a technician measures the chlorine and phosphorus concentrations in the waste water to be 0.5 M and 1.0 M, respectively. Assume (i) that chlorine and phosphorus come only from HCl and phosphoric acid, respectively, and (ii) that no H+ was consumed (or neutralized) in the manufacturing process.
(a) Knowing that the technician has to bring the pH of the waste water back to a minimum of 7.2 before discharging it in the stream, what is the minimum amount (in kg) of NaOH(s) (40 g/mol) that he has to add to the pool before discharging the waste water in the stream?