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An investigation into the amount of Zinc Oxide in Calamine solution

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4An investigation into the amount of Zinc Oxide in Calamine solution Planning In this experiment, I plan to find out how much Zinc oxide is present in Calamine solution (a solution that stops itching). I will do this by working out the amount of Zinc Oxide produced by Zinc Carbonate once it has been heated, causing thermal decomposition and the release of carbon dioxide gas. A carbonate is a salt of carbonic acid when carbon dioxide (CO2) dissolves in water. When combustion takes place, CO2 is a product along with another substance; in our case, zinc oxide. Here is the chemical equation: Zinc Carbonate (s) ==> Zinc Oxide (s) + Carbon dioxide (g) ZnCO3 ZnO CO2 With this, you can find out the theoretical yield that you will receive from the calamine lotion. You do this using the element's relative atomic mass. As the equation has already been balanced, you work out how much (in grams) you will produce. As zinc carbonate is relatively unstable, it is able to decompose into zinc oxide and carbon dioxide. Because zinc oxide is stable, it shall not decompose any further, Therefore, from 125grams of calamine lotion, you will harness 81grams of zinc oxide and 44grams of carbon dioxide. I will discuss the theoretical yield and how to calculate it later on within the method. ...read more.


Therefore, when the bubbling has stopped, so has the reaction. To make the experiment as safe as possible, goggles wwill be used when heating up the zin carbonate within the test tube. To stop the carbonate from spewing out of the top, I will put mineral wool just inside. This lets through the carbon dioxide, but in theory will keep in the zinc carbonate. The test tube will be fixed in an appropriate angle, so that if anything does spill out of the top, it shall not hit anyone. Also, normal lab procedures such as tying lose objects (such as hair, ties etc) back. To make this a fair test, I will change only one variable throughout the process; the amount of calamine lotion in the test tube. Time is not a big factor, as after five minutes, the compound shall be weighed. It will be heated for two minutes at a time until the reaction has finished. The bunsen burner shall always be at the same distance of the test tube, at the tip of the 'blue flame' which is the hottest part. Most importantly, the amounts of calamine lotion shall be weighed nearly exact to 2 decimal places to make it as exact as possible. ...read more.


In theory, the only product that leaves the test tube will be the carbon dioxide so in ideal conditions the results should exactly match the theoretical yields. Evaluation The experiment has been successful because of the accuracy of my results. The procedure that I have used has been right for the nature of the investigation, and the quality of my evidence has been good. The only anomaly, if any was the experiment using 0.6g of calamine lotion. Whereas my percentage yields had varied between approximately !00% to 105%, the percentage yield in this case was 113% which is quite a long way off target for the precision that I was aiming for. To improve this, with time allowing I should have repeated the experiment a further time. The anolomaly could have been due to too much calamine lotion, but for this to happen twice is strange. However, I feel that the reliability of the evidence is sufficient enough to support the conclusion, as I have even calculated an average percentage yield, 103%. This shows that even with the anomaly, the experiment has been very precise. To furthen the investigations scientifical merit, would have been to harness and record the amount of carbon dioxide let loose. Doing this may not be exactly accurate, but even just counting the bubbles emitted by the thermal decomposition would have given us an even better idea of accurateness. ...read more.

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