Experiment 2 Lab Report
This lab used mass and mole ratios in order to write a chemical formula. Empirical formulas can be found if we know the percent mass of the elements and molecular formula can be found if the mass of each is element is either given or calculated. In this experiment we determine mole ratios of x,y, and z by breaking the copper hydrate compound apart.
The Experimental Description
The first thing in the experiment was to measure the out 1.045g of hydrated copper chloride; it was then heated on a bunson burner at that was turned to 3. The hydrated copper chloride was stirred very frequently as it turned from blue to brown, this took about 20 minutes. The result was a smaller mass of dark brown crystals. 10 grams of reverse osmosis water was added to the dehydrated sample, the brown crystals all dissolved almost immediately, which resulted in a clear blue solution. 0 .288g (6cm) of aluminum wire was added to the blue solution, the Al started bubbling immediately and forming copper flakes on the Al wire. I continually scraped the Cu off the wire to give it a newly reactive surface. The reaction started slowing down at about 10 minutes, at 13 minutes the solution started to turn a bit murky with a purple/gray tinge to it. At 17 minutes the reaction was much slower and didn’t seem to be happening at all until the Al was prodded and released a small cloud of bubbles. After about 25 minutes the reaction was over and the Buchner funnel was set up to separate the copper metal flakes that had been created from the solution. Once we got the Cu on the filter paper we let it dry in the oven for about 25 minutes. Once dry the mass of the Cu was determined.
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In the experiment the same scale was used throughout to determine masses. First the mass of the dehydrated sample was determined by subtracting the mass of the beaker+hydrated sample from the mass of the beaker + dehydrated sample to get, 0.806g of dehydrated sample. The mass of Cu was determined by subtracting the mass of the filter paper and watch glass from the Cu on the paper and watch glass. The coppers mass was 0.38g. The Al mass was determined by simply weighing the Al before and after the reaction, 0.183g was used in the reaction. Once we had all these numbers we could determine the moles of each by using their molar masses:
So we are able to get the chemical formula CuCl2 H2O2
There could be systematic errors in the data the numbers are very small and there could be errors in the mass measurements or calculations. One possible error could be in the Cu measurement since there were so many ways Cu could have been lost in the experiment. The precision of this experiment seemed valid but can only be determined by plus or minus 0.0001g. The experiment seemed to be a success since the data worked out in a way where the chemical formula could be determined which was the goal for this experiment.