Detailed procedure 1. Weigh about 5 g of the \"simulated\" ore into a 100 mL con

Question

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 and hydrogen peroxide solution. Effervescence may be observed due to evolution of oxygen gas produced by the decomposition of hydrogen peroxide. If this occurs too vigorously, the bubbles of gas may cause splashing of unreacted hamful 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. . Decant the slurry into a clean beaker and wash the residue several times with a small volume of water. Add these ensure that all the copper-complex is collected. 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 zinc powder as rinsings into the clean beaker to 5. this may make the recovery of the pure copper more difficult. 6. Decant the solution. Wash the residue with deionised water and decant the liquid at least twice. 7. The black residue is a mixture of copper metal and surplus (unreacted) zinc. In the fumehood, remove the zinc by adding about 4 mL of 3 M sulfuric acid solution. Take care as this is a vigorous and exothermic reaction. 8. The residue should now be pure copper. Decant the solution from the residue and wash the residue (decanting the wash liquid) at least twice with deionised water 9. Dry the residue (your demonstrator will guide you through this step) and record the mass of your recovered product.

Explanation / Answer

The unreacted zinc can be removed by addition of sulphuric acid in the mixture obtained.

Care should be taken as the reaction of zinc is slightly exothermic reaction liberating hydrogen gas along with the formation of zinc sulphate. The hydrogen gas is bubbled by out during the reaction.

Zn+ H2SO4-----> ZnSO4+H2

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