Partner: Debnil Chowdhury
TA’s: Russell Dondero & Sylvester Mosley
February 9, 2000
The purpose of this lab was to determine the percent cobalt and oxalate by mass, and with that information, the empirical formula for cobalt oxalate hydrate, using the general formula Coa(C2O4)b.cH2O.
The powdered cobalt oxalate hydrate was weighed to about 0.3 g and placed in a pre-weighed crucible. The crucible and the cobalt oxalate were then heated until the cobalt oxalate decomposed into a stable, black solid, or Co3O4. Once the crucible was sufficiently cooled, the crucible and the new substance were weighed. With this weight, the mass percent of cobalt could be determined. This step was then repeated.
Coa(C2O4)b.cH2O + heat ( Co3O4 A 300 ml 0.5 M sulfuric acid solution was created by adding 25 ml of 6 M sulfuric acid to 275 ml of distilled water. A buret was then cleaned and filled with the KmnO4 solution. Next, 10 to 15 ml of 0.1 M sodium oxalate solution was added to 100 ml sulfuric acid and placed in an Erlenmeyer flask for titration. The solution was then heated to around 60 degrees Celsius. The solution was then titrated until a faint pink/purple color remains for about thirty seconds. The Molarity of the KMnO4 can then be determined. This step was repeated. About 0.3 g of cobalt oxalate hydrate was then weighed (to the nearest 0.1 mg) and placed in an Erlenmeyer flask with 100 ml of 0.5 M sulfuric acid. This solution was then heated to about 60 degrees Celsius. This solution was also titrated with the KMnO4 until a specific color change occurs. With this information, the mass percent of oxalate can be determined. This was repeated.
5C2O42- + 2MnO41- + 16H+ ( 10CO2 + 2Mn2+ + 8H2O
Data and Calculations
|Determination of Cobalt