Engineers in south africa are hired to determine whether a river that passes through a pyrochroite (mn(oh)2) deposit meets the standards for drinking water (drinking water standard for mn = 50 ppb). the river is in contact with solid mn(oh)2 (pksp = 14.3) and has a ph of 8.0. determine the concentration of mn2+ in the river in mg/l. also, determine the ph at which the concentration of mn2+ would meet the drinking water standard. (answers: [mn2+] = 275.2 mg/l; ph=9.87).