2 задачи (решение)

2. 50.0 ml of titrating solution containing ferric iron required 13.7 ml of 0.012 M solution of EDTA at pH = 2 and 29.6 ml at pH = 6. Determine the concentration of ferric iron in mg / ml.
3. In the analysis of iron oxide in a solution of unknown composition of its sample of 0,100 all the iron was reduced to ferrous and then titrated with 13.05 ml of 0.0993 N K2Sr2O7 concentration. What analiziruemogo iron oxide formula: FeO, Fe2O3 Fe3O4?