Aim: To determine the percentage of copper present in malachite.
Hypothesis: That the percentage of copper in the malachite will be four percent.
Materials: 2 x 250mL beaker, pestle, malachite, sulfuric acid, water, 2 x filter paper, funnel, filter stand,
Safety Precautions: Wear safety glasses at all times when dealing with chemicals and apron to avoid ruining clothes.
Record the mass of the malachite sample. Place the malachite into the 250mL beaker and add 20-30mL of dilute sulfuric acid. Wait until the reaction has slowed down and then gently crush the malachite into fine pieces using the pestle. Leave the mixture for about ten minutes stirring occasionally.
When there is no sign of further reaction add about 10mL of water to the mixture. Allow to settle and then filter into the other 250mL beaker. Rinse the residue remaining in the beaker with 10mL of water and filter this too. After all the liquid has been filtered discard the filter paper and unreacted solids.
Place a small amount of steel wool into the beaker and leave overnight.
Note the weight of a piece of filter paper. Filter the solution and rinse the solid copper remaining on the filter paper with 50mL if water. Discard the filtrate. Allow the filter paper to dry overnight and record the mass.
Mass of Malachite 31.1g
Mass of filter paper 1.2g
Mass of filter paper and copper 1.9g
Therefore, Mass of copper 0.7g
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Percentage of copper in malachite sample 2.25%
The experiment went well and there were very few problems. The only experimental difficulty was during the first time the solution needs to be filtered and the filter paper became clogged up and it took a long time to drain through and a small amount of liquid may have not filtered through. The experiment could have been improved by replacing the filter paper when it became blocked with a new piece, making the experiment quicker and more accurate. We did not spill anything so I believe our groups result was accurate, maybe slightly off. The hypothesis was proven incorrect but was very close.
When the malachite and the sulfuric acid have been mixed and filtered part of what happens is:
Cu(OH)2 + H2SO4 –> 2H2O + CuSO4
When the experiment has been finished the chemical reaction is shown in this equation:
Fe + Cu2+ “” Fe2+ = Cu