Method: Gather all necessary apparatus and set up ready for the experiment as shown in the diagram below.
Firstly weigh one of the test tubes (presuming they are not all the same weight) to be certain of each ones weight. Using a spatula measure 2g of calamine into one test tube. Plug the test tube with sufficient mineral wool using tongs to avoid contact with hands and thus avoiding any irritation that may occur. Mineral wool will prevent spillage. Then re-weigh the test tube containing both the mineral wool and the calamine. Record these weights into a table. Simply because we used differing test tubes had to weigh each one separatley to insure our experiment was fair and accurate. Calculate the difference in weight trying to ensure that it was the desired quantity.
Heat the test tube until there is a significant change in colour for 5minutes exactly. This had to be precise as it may have an affect on out reults at a later stage.Leave the test tube to cool for aproximatley 1 minute whilst weighing it and then reheat for another 2 minutes. The reason we reheated the test tube was to be certain that all the zinc carbonate had been compltety heated. Now repeat process for 2.5g, 3g, 3.5g, and 4g of calamine. Check that test tube one has cooled down then weigh and record results. Repeat this heating, cooling and weighing process until the weight of each test tube remains unchanged for two consecutive weighs. Record all final weights, and from results work out how much zinc oxide has been produced in each test tube this can be done with the following equation:
Weight of Zinc Oxide Produced=
Weight of Calamine used - (Starting weight - End weight)
The two weights in the brackets must contain both the calamine and mineral wool.
Results:
Experiment One
Experiment Two
After taking 5 different readings, we decded to repeat the experiment so we could take an average of two readings in order to create a more accurate visual representation in the form of graph. The second set of reults is below.
Evaluating Evidence
Theoretical conversion chart:
ZnCO³ ZnO+CO²(already balanced)
One mole of ZnCO³ gives 1 mole of ZnO
(C=12, O=16, Zn=65)
ZnCO³ ZnO
65+12+48=125 65+16=81
One gram of ZnCO³ gives 81/125=0.648 grams of ZnO
To compare the theoretical conversion chart with the results I gained I will work the percentage yield. This is done by taking the actual amount gained dividing it by the expected amount (theoretical) and times by 100. Here are the percentage yields I worked out.
Analysis of results:
For both the theoretical conversion line and the results I gained line we see that they both show strong positive correlation. Matter cannot be destroyed or created so it is logical that there is direct correlation on the yield generated. I can conclude that these results were to be expected because science says that the amount of zinc oxide produced will be directly proportional to the amount of calamine used. By using the percentage yield table we can see that the amount of Zinc Oxide produced varied bewtween the two experiments but the average values of oth experimens show a direct relationship and conquer with the theoretical amount.The are differences between both experiments and this would be due to one main reason, that measuring of the calamine could have been inaccurate, but because the percentage yields for each of the readings in a particular experiment were all quite similar.
The graph are a clear representation of the results I obtained. You can see ow one experiment gave me a set of results which were below the theoretical amounts and how the other gave me results above the theoretical amounts. This suggests my two experiments were fair because the percentage yields are equal. The cause of this cold have been due to the environment atmoshere for example room temperature. The graph showing the averages of the experiments complies with the theoretical amounts successfully.
Analysing Evidence and Drwaing Conclusions:
Evaluation:
I feel my result were reasonablly accurate and this is because I feel I performed the experiment succesfully and fairly. An example of one of the things which may have affectde my result would have been not measuring each test tubes speraratley and just asuming that the weight was consistent for all of them. There are however still ways in which the experiment could have been improved such as taking a wider range of readings and possibly even using smaller intervals between the readings but this would have been to time conuming and unpractical for a class investigation. We could have also used a different compound in the same group to see if we got similar results.
My results and my graphs support my hypothesis that as the mass of calamine heated increases the more zinc oxide was produced. The graphs also support my hypothesis as they show that the relationship between the amount of calamine heated and the amount of zinc oxide obtained was directly proportional. However, the difference in the amount of zinc oxide produced between each gram of calamine was roughly 0.7g which is 0.1g more that what was expected. This difference caused the % yield to be higher then 100%.
I think that my results were quite accurate as the amount of zinc oxide obtained did consistently increase round 0.7g by each gram of calamine heated. I believe the reason the % yield was higher than 100% because the zinc oxide obtained from the calamine could have not been pure, as the calamine could have had some impurities in it to begin with. This could have been caused as although the test tube and its contains were heated and weighed repeatedly until the mass remained the same for two consecutive weightings, the calamine could have needed a higher temperature applied to it to fully complete the reaction. This is why I reapeated the experiment and then achieved a new set of results which were all below the the theoretical amounts. The mineral wool, (used to stop small particles of zinc oxide escaping with the CO₂) could have also stopped other matter in the calamine (which is not used for producing zinc oxide) from escaping.
I think my results were also quite reliable as there wasn't very much scatter on my graph, all the points were close to my line of best fit. I also believe my results were reliable as the differences between the results in the first experiment and the results in the second were quite small. An exception to this was the experiment for 3g of calamine in experiment 1 the amount of zinc oxide obtained was 2.19 and in experiment 2 the amount obtained was only 1.7, a difference of 0.5g. If I could re-do this experiment I would like to repeat the whole experiment for a third time or at least do a third test using 3g of calamine, this would improve the accuracy of my results as it would help determine anomalous results, which would let me have the choice to not include it in my averages results. This reslut wasn’t necessary anomoulous when considered as an average of the two experiments but it was the closest I got to having an anomolie.
