Experiment 10 & 11

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 Experiment #10 & #11

The Synthesis of Cobalt Oxalate Hydrate
The Synthesis of a Nitrite Complex
 
February 5, 2012
 
Chemistry 1211L - 146 - Spring 2012
 

Procedure
The Synthesis of Cobalt Oxalate Hydrate
Place 100 ml of distilled water in a 250-ml (or 400-ml) beaker. Add 1.26g of oxalic acid dihydrate (H2C2O4.2H2O) and 1 ml of concentrated ammonia. Stir the mixture until the solid has dissolved completely. Dissolve 2.34 g of cobalt chloride hexahydrate (CoCl2.6H2O) in 100 ml of water in an Erlenmeyer flask. While stirring the oxalic acid solution constantly, add the cobalt chloride solution drop by drop. Let the mixture cool in an ice bath. A precipitate will form slowly. After the precipitate has had a chance to settle, collect it by gravity filtration. Wash the collected solid sparingly with cold water. Allow the water to drain from the collected solid. Then transfer the filter paper and precipitate to a paper towel so that excess moisture can be absorbed. Before you leave the lab, place your precipitate (still in its filter paper cone) in a beaker and leave it in your desk to air dry for at least three days. After your precipitate has dried thoroughly, weigh it on the analytical balance.

The Synthesis of a Nitrite Complex
Obtain an assignment of transition metal and non-transition metal from your instructor. Weigh out 0.005 mole of the designated non-transition metal chloride and 0.005 mole of the designated transition metal chloride. (Remember to consider the numbers of waters of hydration in calculating the desired masses of the assigned salts.) Dissolve the two in a minimum volume (about 5 ml total) of distilled water, with low heat only if needed to dissolve the salts. Weigh out 0.05 mole of KNO2, dissolve it in 5 ml of water, and then slowly add this solution, while stirring, to the solution of metal chlorides. Cool the mixture in an ice bath. Allow the solid to settle, then decant the supernatant liquid into a filter funnel, leaving most of the solid in the original beaker where it can be washed more efficiently. Add a 3-ml portion of cold water containing a small amount of KNO2 to the solid, stir well, and pour the mixture onto the filter to collect the product. When the water has all drained out of the filter, pour 5 ml of acetone over the solid to help dry it. Pour a second 5-ml portion of acetone over the solid after the first has drained through the filter. Complete the drying of your compound by drawing a gently stream of air through the filter using an aspirator. If no aspirator is available, open the filter paper and spread out the solid to dry in the air. The product is dry when it is powdery and has no odor of acetone. The procedure used for those syntheses is identical to that described in: Block/McKelvy/Denniston/Silverstein (2008). Laboratory Experiments for Chem 1211L & 1212L Cengage Learning p.55 & p.64 (the Synthesis of Cobalt Oxalate Hydrate & the Synthesis of a Nitrite Complex) Data

The Synthesis of Cobalt Oxalate Hydrate
Mass of CoCl2.6H2O: 1.17 g
Mass of H2C2O4.2H2O: 0.63 g
Volume of NH3: 0.5 ml
Mass of product (CoC2O4.2H2O): 0.500 g

The Synthesis of a Nitrite Complex
Mass of NiCl2.6H2O: 0.59 g (0.0025 mol)
Mass of SrCl2.6H2O: 0.67 g (0.0025 mol)
Mass of KNO2: 2.13 g (0.025 mol)
Mass of product (K2SrNi(NO2)6): 0.500 g

Calculations
The Synthesis of Cobalt Oxalate Hydrate
Equation:
CoCl2.6H2O + H2C2O4.2H2O + 6 NH3 -> CoC2O4.2H2O + 6 NH4OH + 2 HCl Find limiting reagent:
# mol CoCl2.6H2O = 1.17g CoCl2.6H2O x 1 mol CoCl2.6H2O 237.9 g CoCl2.6H2O=0.00492 (mol)
# mol H2C2O4.2H2O = 0.630 g H2C2O4.2H2O x 1 mol H2C2O4.2H2O 126 g H2C2O4.2H2O =0.005 (mol) Assume CoCl2.6H2O is limiting reagent
1 mol CoCl2.6H2O -> 1 mol CoC2O4.2H2O
# mol CoC2O4.2H2O formed = # mol CoCl2.6H2O = 0.00492 (mol) Assume H2C2O4.2H2O is limiting reagent
1 mol H2C2O4.2H2O -> 1 mol CoC2O4.2H2O
# mol CoC2O4.2H2O formed = # mol H2C2O4.2H2O = 0.005 (mol)
So...
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