This experiment is going to see how much zinc oxide can be obtained from calamine. It shall also show how close to the conversion can be achieved in practice.
Hypothesis
In a previous experiment where copper carbonate was obtained from malachite the results showed that as the more malachite was used the more product was produced. The relationship between the mass of malachite used and the amount of copper oxide obtained was proportional. Malachite and calamine are next to each other in the periodic table and therefore are alike so I predict that the more calamine used the more zinc oxide will be produced. The theoretical conversion graph also supports this idea. In this experiment I also think that the relationship between the calamine used and zinc oxide produced will also be proportional. Using the theoretical conversion graph I can predict that from every gram of calamine heated about 0.6g of zinc oxide will be produced.
Plan
Apparatus; boiling tube, plug of mineral wool, tongs, calamine, heatproof mat, safety goggles and a Bunsen burner.
Method
- A test tube and a plug of mineral wool are weighed.
- A gram of calamine is weighed and then placed in the test tube. The wool is then placed over the top of the boiling tube.
- The boiling tube is then gently heated over a Bunsen burner until all the white calamine changed to yellow.
- The calamine is left to cool and then the tube is weighed.
- The calamine is heated for a further 2 minutes, then cooled and re-weighed. If the mass of the boiling tube remained the same as the last time it was weighed then that mass is recorded. If the mass is different the calamine is heated for another 2 minutes and then cooled and re-weighed. The calamine continues to be reheated until the mass stays the same in two consecutive weightings.
The above method is repeated with 2g, 3g, 4g and 5g of calamine. The whole experiment is then repeated.
Safety
Safety goggles are to be worn during the experiment, to protect eyes from dangerous fumes produced from using the Bunsen burner. Tongs should also be used to handle the mineral wool and to hold the boiling tube over the Bunsen burner flame to avoid injury.
Results
Conclusion
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%.
Evaluation
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. 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 4g of calamine in experiment 1 the amount of zinc oxide obtained was 3.34 and in experiment 2 the amount obtained was only 2.64, a difference of 0.7g. 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 4g 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.
I am fairly proud of my experiment and believe if I had had more time and better quality resources my results would have been much more accurate and reliable.
