Dr. Hjorth-Gustin

Chemistry 201 Lab

November 8th, 2010

Synthesis and Analysis of Iron(III) Oxalate Complex Discussion

This experiment initially involved the synthesis of an iron (III) oxalate complex with the general formula Kw[Fex(C2O4)y] zH2O. The variables x, y, and z were determined

through the duration of the entire experiment. Part 1 involves the synthesis of an iron (III) oxalate complex. The iron is first presented in its Fe2+ form, so it must first be oxidized to

Fe3+ before the oxalate ion will readily bind to it. Hydrogen peroxide is the oxidant of choice: 2Fe2+ (aq) + H2O2 (l) + 2H+ (aq) ---> 2Fe3+ (aq) + 2H2O (l), in acidic solution.

The oxalate ion is then free to coordinate to the Fe3+ ion, forming a complex of Fe(C2O4). The oxalate ion is the conjugate base of the weak oxalic acid, H2C2O4.

In the synthesis of the iron (III) oxalate complex, 0.8668g of the final lime-green crystals were obtained. The average percent of C2O4 was 59.00% and the theoretical yield

was 53.74%. With this, the percent error came out to 9.79%. The percentage of Fe(III) in the green crystal obtained was 14.5%. Theoretically, it should have been around 10%.

This lack of accuracy was quite difficult to recognize considering the calculations were approved by the professor but may have been due to incorrectly preparing the buffer.

Apart from the usual human-mediated errors in the measuring and distribution of chemicals and in the readings of instrumental information, additional sources of error may have

been caused by dirty and/or improperly calibrated glassware, failure to completely encase the crystals in foil (crystals are light-sensitive), improper cleaning of the crucible (which

would lead to inaccurate filtration), contaminated or already-catalyzed H2O2 (which would result in the hindered oxidation of Fe2+ to Fe3+), and