Qualitative Analysis of Cations Overview Getting Started Techniques Procedure FAQ Full Lab Manual Introduction & Goals Chemistry & Background Key Questions Prelab Problems Safety Procedure In Your Write-up Experiments Index ChemLab Home		FAQ Index Question 1 I'm am having problems with the Qualitative Analysis of Cations Applet. I am analyzing Unknown solution B, which is supposed to have two cations (Revealed as Pb+2 and Fe+2). However, when I add the water (there is no option for hot water) to separate the AgCl from the PbCl, a white precipitate remains. Also, if I centrifuge and test the centrifugate with potassium chromate a bright yellow precipitate does not occur (there is no reaction). Question 2 How can I be sure I removed all the Group I ions, before continuing with the analysis of Group II and III ions? Submissions Submit a question or an answer to the FAQ Questions & Answers Question 1 I'm am having problems with the Qualitative Analysis of Cations Applet. I am analyzing Unknown solution B, which is supposed to have two cations (Revealed as Pb+2 and Fe+2). However, when I add the water (there is no option for hot water) to separate the AgCl from the PbCl, a white precipitate remains. Also, if I centrifuge and test the centrifugate with potassium chromate a bright yellow precipitate does not occur (there is no reaction). Professor Milde Here is a quick answer, but you should consult your TA or come to TA office hours today, if you want further help. Add water to the precipitate that contains AgCl and/or PbCl2. Then HEAT it in the water bath and centrifuge the hot mixture. This will allow you to separate the insoluble AgCl and the soluble Pb2+ cations that might be present. The applet should work fine, once you try this method. Question 2 How can I be sure I removed all the Group I ions, before continuing with the analysis of Group II and III ions? Professor Milde It is important to remove all the Group I ions, so that they don't obscure the Group II and Group III results. The solution containing Groups II and III cations must be completely clear after the Group I precipitates are removed. You can add some additional HCl to see if more Group I chloride solids form. You can also let the test tube sit, while you confirm you Group I ions, to see if more precipitate settles out of the Group II and III solution. If more lead or silver chloride forms, remove it by centrifugation, before continuing the Group II and III analysis. Submissions Submit to the FAQ You can submit either a question or an answer to a question about this week's experiment. Your submission will be mailed to the site editor, who will respond to you directly and also add your submission to the FAQ page. Having trouble with the submission procedure? Check your Kerberos installation. If you lose the FAQ Submission window it may be hidden behind another browser window.
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