2 6M acetic acid is added dropwise and stirred to dissolve the precipitate 3 A

2 6m acetic acid is added dropwise and stirred to

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2. 6M acetic acid is added dropwise and stirred to dissolve the precipitate.
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3. A few more drops of 6M acetic acid is added until it is acidic. 4. 6 drops of 1M K 2 CrO 4 is added to the solution and stirred. 5. Centrifuged the precipitate when chromate is formed. 6. The supernatant is saved for next procedure D(ii). Procedure D(ii) 1. 10 drops of 1M K 2 C 2 O 4 is added to the solution and stirred for 10 minutes. 2. Centrifuged the precipitate when oxalate is formed. Result
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Experiment Observation On adding HCl to the initial sample Mixture White precipitate is formed Unknown 1 No precipitate Unknown 2 No precipitate On adding H 2 S under acidic condition Mixture Turn black and pungent Unknown 1 Clear Unknown 2 Clear On adding H 2 S under basic condition Mixture Black precipitate is formed Unknown 1 No precipitate Unknown 2 No precipitate On adding CO 3 2- Mixture Clear Unknown 1 Clear Unknown 2 Clear On adding CrO 4 2- Unknown 1 No precipitate Unknown 2 No precipitate Metal cations No precipitate On adding C 2 O 4 2- Unknown 1 No precipitate Unknown 2 No precipitate Metal cations No precipitate Discussion
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Based on the result, we can predict the solution for the mixture, unknown I and unknown II solutions. Let us begin with the mixture. When the mixture is mix with HCl, a white precipitate is formed. Based on the diagram given in our manual, the precipitate is Ag + ion. The net equation for this reaction is:- Ag + + Cl - AgCl (s) In procedure B, adding of hydrogen sulfide, H 2 S into the solution under acidic condition gives grayish-black precipitate. The solution is made to be acidic in order to prevent the other metal sulfides from other groups to precipitate. Our result for the Procedure B is the solution turns black and pungent, but there is no precipitate formed. But we should see a grey precipitate to confirm the present of copper(II) ion. It might be we missed the precipitate while we observed
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