- The supernatant liquid of this step is to be tested and adjusted to be basic. We separate the supernatant from the residue and add drop wise 6M NH 3 until the orange alkacid paper turns blue. - Then we add 2 drops of 1 M thioacetamide and heat for 2 minutes. Record observations - The separated residue is to be mixed with 10 drops of H 2 O and 10 drops of 6M HNO 3 , and then heated for 5 minutes in the water bath. - We decant the liquid and record observations for the color of the residue. - The liquid is than mixed with 6M NH 3 , until the solution turns basic to pH 8. - Then add 10 more drops of 6M NH 3 , and cool. - We add more drops of 6M NH 3 until the pH becomes 10. - We then centrifuge for 2 minutes. - We separate the supernatant and the residue and record observations. - Finally, we add 10 drops of 6M NH 3 , and centrifuge again. - The supernatant is discarded and we record observations for the residue. - --------------------- - The entire procedure is repeated for the unknowns. Observations: Since this was a large experiment several observations were to be recorded based on looking at the color of the residue or testing the supernatant liquid at times. The initial experiment was broken into two parts, part 1 was to test for the known cations and part 2 was to test for the unknown cations presented in an unknown solution. To test for the selected group II cations, we broke the experiment into 4 parts. A. Confirming Sulfides. Known: The known solution was presented to us as a clear solution which turned brown after the addition of thioacetamide. To find out if it had sulfides, we performed some preliminary steps and boiled the mixture in water. The color of the mixture turned black at this point confirming the presence of sulfides. Unknown: To isolate the sulfide from the solution was a bit more complex since Bi 2 S 3 was a compound that was left to be separated in the end. In this case, Sulfide was the final left
over residue after separating all the other cations. We confirmed the presence of the sulfide
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- Summer '15
- Chemistry, supernatant liquid, Jahnavi Shah