- Title: Group I & Group II Cation Identification
- Purpose:
I will identify the unknown cations from the alkaline earth metals. Threw qualitative analysis.
- Hypothesis:
I should be able to identify the unknown cations.
Variables:
Control: Solubility rules & double-displacement reactions based on solubility rules.
Dependent: Unknown Ions in the solution
Independent: Various chemical environments induced to identify unknown
- Materials:
- Chemicals
- 6 M HCl
- 12 M HCl
- 6 M HC2H3O2
- 1 M K2CrO4
- 6 M NH3
- 6 M HNO3
- 3% H2O2
- 6 M NaOH
- 1 M NaOH
- 1 M thioacetamide
- 1 M NH4Cl
- 0.5 M NaC2H3O2
- 0.1 M SnCl2
- 0.3 g of solid Na2S2O4 (sodium hydrosulfite)
- 0.4 g solid sodium thiosulfate (Na2S2O3)
- Red & blue litmus paper
- Tap water
- Distilled water
- Dionized water
- Stirring rods
- Safety glasses
- Test tubes
- Balance
- Large beaker
- 50-ml Beaker
- Boiling water bath
- Sink
- 5-mm length of heavy copper wire
- 1-cm length of 24 gauge of aluminum wire
- Centrifuge
- Hot pads
- Metal spatulas
- Medicine droppers
- Test tube holders
- Procedure:
Group I Cations
Step 1:
- Add 0.5 ml 6 M HCl to 3 ml of a sample in the test tube.
- Stir well and centrifuge.
- Decant the liquid, which may have ions, into a test tube.
- Save the test tube for further analysis.
- Make sure precipitation for Group I cations was complete by adding 1 drop of 6 M HCl into the liquid.
- Wash the precipitate with 2 ml water and 2 drops of 6 M HCl.
- Stir well.
- Centrifuge and throw away the wash liquid.
- Re-wash the precipitate with water and HCL.
- Throw away the liquid.
Step 2:
- Add about 4 ml water to the precipitate from Step 1, which contains the chlorides of the Group I cations.
- Heat the precipitate in a boiling water bath for at least three minutes.
- Stir repeatedly.
- Centrifuge quickly.
- Decant the liquid, which may have Pb2+, into a test tube.
Step 3:
- Add 2 drops of 6 M acetic acid and 3-4 drops of 1 M K2CrO4 into the liquid from Step 2.
- Centrifuge out the solid to help with the identification.
Step 4:
- Wash the precipitate from Step 2 with 6 ml water in the boiling water bath if lead is present.
- Centrifuge and test the liquid for Pb2+.
- Continue washing until no positive reaction to the lead test is obtained.
- Add 2 ml 6 M NH3 to the washed precipitate.
- Stir well.
- Centrifuge and decant the liquid, which may contain Ag(NH3)2+, into a test tube.