In the procedure 5,what specific observation can be made to confirm whether or n
ID: 702697 • Letter: I
Question
In the procedure 5,what specific observation can be made to confirm whether or not sufficient zinc powder has been added? Detailed procedure 1. Weigh about 5 g of the "simulated" ore into a 100 mL conical flask, then add about 20 mL of a 5%, aqueous solution of ethylenediamine 2. In the fume hood, with continuous swirling, add successive portions of about 0.5 mL of 3% (10 volume) hydrogen peroxide solution. Allow bubbling to subside between additions. The bubbling is due to evolution of oxygen produced by decomposition of hydrogen peroxide. Care should be exercised when handling the ethylenediamine solution ar hydrogen peroxide solution. Effervescence may be observed due to evolution oxygen gas produced by the decomposition of hydrogen peroxide. If this occurs t vigorously, the bubbles of gas may cause splashing of unreacted harmt ethylenediamine. Continue to add the small portions of the hydrogen peroxide solution until a total of 20 mL is added. Swirl for another 5 minutes, then allow the mixture to settle 3. 4. Decant the slurry into a clean beaker and wash the residue several times with a small volume of water. Add these rinsings into the clean beaker to ensure that all the copper-complex is collected. 5. Add a pea-sized sample of powdered zinc and stir the solution until all the copper has been displaced. If the displacement is not complete after a short while, more zinc may be added - Do NOT add too much zino powder as this may make the recovery of the pure coppe r more difficult.Explanation / Answer
Answer:
Presence of copper in solution make it blue in color. when we add zinc powder in this solution some heat release which we can feel by touching the flask. simultaneously solution which was blue in color become colorless after reaction of zinc and copper, zinc powder also changes its color to orange. If copper solution is not completely colorless means still some more addition powder zinc is required.
Confirmation:
Additional test:
A NaOH addition test is performed to identify presence of ions in solution.
Sodium hydroxide is added in the solution and a precipitate is obtained which is not blue but white.
This test result confirms that copper ions have disappeared from the aqueous solution and have been replaced with zinc ions which form a white precipitate with sodium hydroxide.
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