Qualitative Analysis: Group I

CHM 101/102CHM 101/102

Laboratory ManualLaboratory ManualLaboratory Manual

Qualitative Analysis: Group IQualitative Analysis: Group I

General Chemistry 101/102General Chemistry 101/102Laboratory ManualLaboratory Manual

University of North Carolina at WilmingtonUniversity of North Carolina at Wilmington

CHM 101/102CHM 101/102



• PurposePurpose To study the chemical properties of AgTo study the chemical properties of Ag++, Pb, Pb2+2+, and , and

HgHg222+2+ ions and the compounds they form. ions and the compounds they form.

Use the chemical properties of these ions to Use the chemical properties of these ions to identify their presence in an unknown mixture.identify their presence in an unknown mixture.

• Safety ConsiderationsSafety Considerations

PbPb2+2+ and Hg and Hg222+2+ ions are very toxic. ions are very toxic.

Wash your hands thoroughly after this experiment.Wash your hands thoroughly after this experiment. Place all waste solids and solutions in the Place all waste solids and solutions in the

appropriately labeled containers in the hood.appropriately labeled containers in the hood.

CHM 101/102CHM 101/102



• General ProceduresGeneral Procedures Use clean glassware and deionized water to avoid Use clean glassware and deionized water to avoid

contaminating your sample.contaminating your sample.

Distinguish between Distinguish between clear, cloudy, colored, clear, cloudy, colored, and colorless in your and colorless in your descriptions.descriptions.

cloudy yellowcloudy yellow

clear yellowclear yellow

clear colorlessclear colorless

white solidwhite solid

CHM 101/102CHM 101/102



• General ProceduresGeneral Procedures Exercise caution when Exercise caution when

using the centrifuge. Use using the centrifuge. Use a counterbalance tube.a counterbalance tube.

samplesample counterbalancecounterbalance

CHM 101/102CHM 101/102



Use a water bath to heat all Use a water bath to heat all mixtures.mixtures.

• General ProceduresGeneral Procedures Pay attention to whether you are to keep Pay attention to whether you are to keep

or discard the or discard the precipitateprecipitate and/or and/or supernatantsupernatant..

supernatantsupernatant

precipitateprecipitate

CHM 101/102CHM 101/102


• BackgroundBackground

AgAg++, Pb, Pb2+2+, and Hg, and Hg222+2+ ions all form white precipitates ions all form white precipitates

with Cl with Cl -- at room temperature. at room temperature.


6 M HCl6 M HCl

AgCl, PbClAgCl, PbCl22, Hg, Hg22ClCl22

CHM 101/102CHM 101/102



PbClPbCl22 is insoluble in cold water but soluble in hot is insoluble in cold water but soluble in hot

water. PbClwater. PbCl22 can be separated from AgCl and can be separated from AgCl and

HgHg22ClCl22 by heating the mixture. by heating the mixture.


PbPb2+2+ ions can be ions can be precipitated with Kprecipitated with K22CrOCrO44. .

PbCrOPbCrO44 is insoluble in hot is insoluble in hot

and cold water.and cold water.

PbCrOPbCrO44

CHM 101/102CHM 101/102




When NHWhen NH33(aq)(aq) is added to a mixture is added to a mixture

of AgCl and Hgof AgCl and Hg22ClCl22, the AgCl , the AgCl

dissolves and a gray-black mixture dissolves and a gray-black mixture of Hg and HgNHof Hg and HgNH22Cl is formed.Cl is formed.

AgAg++ ions can be precipitated ions can be precipitated as AgCl by the addition of as AgCl by the addition of HNOHNO33..

CHM 101/102CHM 101/102



Qualitative Analysis: Group I

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