Lab Report for Qualitative Analysis of Group I Cations PDF

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Lab Report for Qualitative Analysis of Group I Cations...

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Lab Report for Qualitative Analysis of Group I Cations Experiment #8 Chem 102-C502 October 29, 2020

Oyinda Adeyemo Lab Instructor: Professor Daria Rice Date: October 12, 2020

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Purpose To become familiar with the chemical properties of the following dissolved cations: Ag+, Pb2+, Hg2+ Chemical Index Name of chemicals Silver (+1) cation Lead Mercury (1+) ion Hydrochloride acid Potassium Iodide Ammonia Nitric Acid

Molecular Formula Ag+ Pb+ Hg+ HCl KI NH3 HNO3

Molecular Weight 107.868 g/mol 207.2 g/mol 200.59 g/mol 36.46 g/mol 166.0028 g/mol 17.031 g/mol 63.01 g/mol

Equipment Centrifuge tubes, centrifuge, waste beaker, test tubes, litmus paper Procedure I – G1-1 Precipitation of Group I Cations 

Measure out 10 drops of each of the three-test solution into a small centrifuge tube

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Add 10 drops of 6M HCl, stir and centrifuge

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Test for completeness of precipitation by adding 1 drop of 6M HCl to the supernatant

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If supernatant turns cloudy, add two more drops of 6M HCl, stir and centrifuge

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Repeat this process until no more precipitate forms

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Decant the supernatant into a test tube and discard

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Wash the precipitate by adding 5 drops of cold distilled water and stir

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Centrifuge and decant the supernatants

Procedure II – G1-2 Separation and Identification of Pb2+

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Add 15 drops of hot water to the precipitate and place the test tube in a hot water bath

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Stir Stan and heat solution for a minute

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Centrifuge and decant the supernatant into a clean test tube

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Repeat this procedure two more times and combine the supernatants into the same test tube

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Save the precipitate for procedure G1-3

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Add 3 drops of 1M of KI to into the test tube

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A yellow or orange precipitate should be formed confirming that Pb2+ is present in the PbCl2 solution

Procedure III – G1-3 Separation and Identification Ag+ & Hg2+ 

At 10 drops of 6M NH3 to the precipitate from G1-2

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Formation of a dark grey ppt indicates the presence of mercury

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Centrifuge and decant the clear supernatant into a clean test tube

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Add 20 drops of 6M HNO3 to decant

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Stir the solution and test for its acidity

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Continue to add a HNO3 dropwise until the solution is acidic and white cloudiness indicates the presence of Ag+

Testing the Unknown Measure 30 drops of the unknown solution Repeat steps G1-1 through G1-3 Identify the cations present in the known based on observation

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Data:

Conclusion

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The cations present in the unknown solution were Pb2+ and Hg2+. Ag+ wasn’t present in the experiment even after procedures were repeated. During the test to find Ag+, when HNO3 was added dropwise, the solution had 2 layers, the upper layer was clear while the lower layer had dark grey precipitate in it. This indicates that Hg2+ was still present in the solution. The known solutions had three Pb2+, Hg2+, Ag+ cations present in the solution. The purpose of the experiment was performed and understood. One error noticed during the experiment was during the decantation of the liquid to test for the Ag+. When the liquid was transferred, the mercury was all around the centrifuge tube which might have allowed part of the mercury to transfer into the tube. Sources of error noticed during this experiment will be avoided during future experiments. One equipment used during the experiment was the centrifuge. A centrifuge is a device that us used in the separation of fluids. In hospitals, a centrifuge can be used to separate red blood cells, plasmas and platelets. A daily life application of a centrifuge is a washing machine. After the clothes have been washed, the machine spins for a few minutes in order to separate the water from the clothes...