EAS Outreach - Teaching Children Science
EAS Student Emily Saad took an opportunity to teach young scientists about basic experiments and science safety. "We titrated ferrous sulfate (FeSO4) with potassium permanganate (KMnO4), which is dark purple. As KMnO4 (aq) is added to FeSO4 (aq), Fe is oxidized from the +2 to the +3 oxidation state, and Mn is reduced from the +7 to the +2 oxidation state, which results in a colorless solution. The overall reaction is MnO4- + 5Fe2+ + 8H+ ⇌ 5Fe3+ + Mn2+ + 4H2O. Once the Fe2+ has all been converted to Fe3+, Mn7+ is no longer reduced, and the slightest excess of MnO4- causes the solution to turn from colorless to pink. Using the amount of KMnO4 added up to the color change point, we were able to determine how much FeSO4 was present. The solutions in the picture are much darker than pale pink because we then continued adding KMnO4 to show that in extreme excess, the dark purple color of KMnO4 will persist because no further reaction can happen."