ABSTRACT:
In this lab, 0.010 M purple-colored potassium permanganate solution was standardized by redox titration with iron (II) ammonium sulfate hexahydrate (FAS). The average mass of the three flasks of FAS was 0.483 grams. Once the concentration of the standard solution of KMnO4 (aq) was determined, it was used to determine the concentration of Fe2+ in iron pills. On average, there was 0.01813 L of solution used. With this information and the balanced net-ionic equation 10Fe(NH4)2(SO4)2*6H2O+2KMnO4+H2SO4 --> 5Fe2(SO4)3+(NH4)2SO4+K2SO4+2MnSO4+H2O, the average percentage by mass composition of Fe2+ in iron pill samples was 16.99%. (103)
INTRODUCTION:
The scientific concept of this lab was to titrate potassium permanganate with iron (II) ammonium sulfate hexahydrate in order to oxidize the Fe2+ to Fe3+. Then the concentration of the standard solution of KMnO4 (aq) will be used to determine the concentration of Fe2+ in iron pills. The purpose of the lab is to first standardize a stock KMnO4 (aq), and then determine the percentage Fe2+ in iron pills. The expected outcome of this lab was for the percentage of Fe2+ in the iron pills to be 17%. This is what was on the bottle of iron pills, and the point of the lab was to use titration to retrieve as much if the iron as possible.
MATERIALS AND METHODS: The procedure for the standardization of KMnO4 (aq) was to first fill a clean 50 mL buret with 0.0100 M KMnO4 (aq). Three clean Erlenmeyer flasks needed to be labeled, and a piece of FAS needed to be weighed to 0.5g on a piece of weighing paper. Flask 1 was tarred and tapped into the FAS. The mass was then recorded. This was then repeated with flask 2 and 3. 10 mL of water and 5 mL of 3M H2SO4 was added to the three flasks. 50 mL of water was put in a beaker and 1 drop of permanganate solution was added. The color intensity of the mixture matched the standard and remained for 5 seconds or more. The initial volume was recorded to 0.01 mL.