Limiting Reagents Lab Essay
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Problem: What mass of precipitate will form when 1.69g of CuCl2.2H20 reacts with 1.31g of aluminium?
Aspect 3: Materials:
> 150 mL beaker
> Erlenmeyer Flask
> 100ml Graduated Cylinder
> Electronic Balance
> Stir Rod
> Aluminum Foil
> Distilled Water
> Rinse beakerwith distilled water.
> Mass 1.69g of CuCl2.2H2O.
> Add to beaker and add 50mL of distilled water.
> Mass aluminum. Fold in 1/2 & coil loosely.
> Place in beaker and let sit overnight.
> Pull out Aluminum and rinse into beaker
> Mass filter paper, put name on it
> Put paper in funnel and funnel into the Erlenmeyer flas.
> Pour in mixture. Rinse beaker three times.
> Rinse funnel and paper twice.
> Remove Paper and let dry overnight.
> Mass filter paper
Data Collection and Processing (DCP)
Aspect 1: Recording Raw Data:
Mass of CuCl2.2H2O – 1.93g
Mass of Al – ? (The massing of the aluminum was forgotten)
Experimental mass of precipitate = .69g
Aspect 2: Processing Data
2Al(s) + 3CuCl2.2H2O –> 3Cu(s) + 6H2O(l) + 2AlCl3(aq)
M Al= 26.98 g/mol
m 3CuCl2.2H2o = 1.69 g
M 3CuCl2.2H2o = 152.47 g/mol (Chem 20 Data Booklet)
m Cu = ?
n CuCl2.2H2O = 1.93g / 170.49 g/mol
n CuCl2.2H2O = .011320312 mol
3 mol CuCl2.2H2O = 3 mols Cu
n Cu = .011320312 mol
m Cu = .011320312 mol x 63.55 g/mol
m Cu = .719g
% yield = .69 / .719 = 96%
Experimental mass of Cu(s) precipitate = .69g
Theoretical mass of Cu (s) precipitate = .719g
% yield = 96%
Conclusion and Evaluation (CE)
Aspect 1: Conclusion: The mass of precipitate that forms when 1.93g of CuCl2.2H20 reacts with 1.31g of aluminum is .69 g. The % yield was 96%. The massing of aluminum was forgotten but when another piece was massed and the numbers were worked out, it was shown that there was an excess of aluminum and that the CuCl2.2H2O was the limiting reagent.
Aspect 2: Evaluate: There were .029g of Cu precipitate less than expected. It is likely that some of the copper went into the Erlenmeyer or was stuck on the funnel. Despite thorough rinsing of the filter paper, some of the precipitate got through the filter paper and into the Erlenmeyer.
Aspect 3 Improving Experimental Design: Instead of one piece of filter paper, two pieces should be used. This would lead to less precipitate going into the Erlenmeyer. Also, the water in the Erlenmeyer could be re-filtered.