1. FeCl3(s) is often added as a flocculant to water in treatment plants. Determine the pH and dissolved iron concentration if XXXXXXXXXXM FeCl3 were added to pure water. Assume that ferrihydrite,...

1. FeCl3(s) is often added as a flocculant to water in treatment plants. Determine the pH and dissolved iron concentration if 10-4.0 M FeCl3 were added to pure water. Assume that ferrihydrite, Fe(OH)3(s), is the only solid that forms. The Ks for Fe(OH)3(s) is 10-38.8. To solve this problem, start by considering the charge balance, which will include the hydroxy-complexes, and eliminate those complexes which have concentrations that would be expected to be negligible at the expected final pH. Also, remember that the concentration of the free metal, [Fe3+], is controlled by presence of the solid. 2. A closed solution contains total sulfide (S2-Tot) equal to 10-6.0 M and total carbonate equal to 10-5.0 M. In this solution, two solids could be formed, MnS (Ks = 10-17.13) and MnCO3(s) (Ks = 10-10.58). a. At pH = 9, what are the values of [S2-] and [CO32-]? The pKa values for the carbonate system are 6.33 and 10.33 and for H2S are 6.99 and 12.92. The expressions for α0, α1 and α2 are presented below.

b. For the conditions determined in part a, which solid will dominate?