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To investigate Dalton’s law of constant composition

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Planning of the experiment to investigate Dalton's law of constant composition Dalton in the eighteenth and nineteenth century stated that all pure samples of the same chemical compound contain the same proportions of mass As various copper compounds are readily available for laboratory use, the decision has been made to produce copper from black copper oxide and produce black copper oxide from copper by various methods, and to analysis the findings from this to see that the law of constant composition holds true. No other method or data was found to show or prove Daltons theory was true so the decision to use copper and black copper oxide was the best immediate solution. In the preliminary work, various ways of testing Dalton's theory was researched and tested: * Copper Nitrate (from which copper oxide will be made to make copper) * Copper Hydroxide (from which copper black oxide will be made to make copper) * Copper Carbonate (from which black copper oxide will be made to make copper) * Copper (can be oxidized to form black copper oxide) My variable will be different methods of making black copper oxide, and in my results, I aim to see whether this affects the mass ratio of copper to oxygen in the copper oxide from various methods of creation. ...read more.


This table will be set out much like the one below: Source of black copper oxide Copper Hydroxide Copper Nitrate Copper Carbonate Copper 1 2 3 4 5 6 7 8 Mass of: Test tube/ crucible Test tube + copper/ copper oxide before heating Test tube + copper/ copper oxide after heating Copper oxide Copper Oxygen Then, using the table, the results will be laid out on a graph for each experiment with the amount of oxygen against the amount of copper on the x and y axis of the graph. Then the trends from each experiment are to be compared to see if the same trend is seen in each of the results from different experiments on the same graph (and separately to show individual results clearly). An example (with simulated results) is below. Prediction The results about show my prediction of a correlation between the results of oxygen and copper, with a direct relationship. I believe that there will be a direct correlation between the mass of the copper and of the oxygen with a constant mass ratio of copper to oxygen, as because if there was several formulas for black copper oxide, their will not be the same substance. Their will be a different atomic arrangement resulting in a different substance, which will have different properties if not appearance such as red copper oxide Cu2O. ...read more.


It must also be heated in a fume cupboard because of the harmful gases give off. The rest of the copper compounds must be heated slowly until the powder turns black. Copper Carbonate HEAT Copper Oxide + Carbon dioxide Copper Hydroxide HEAT Copper Oxide + Water Copper Nitrate HEAT Copper Oxide + Nitrogen dioxide DIAGRAM Creating Copper Oxide from Copper Firstly, the crucible will be weighed accurately. A crucible (without a lid) is used so that the air can get good access to the copper. Then different weights of 0.75 grams 1.00 grams, 1.25 grams, 1.5 grams and 1.75 grams of copper powder (powder for a large surface area for a oxidation reaction) will be added as before (as separate experiments). As a digital balance only measures to two decimal places, and if these weights are used they will only be about a 1% error in measurement (an error of 0.01 is equivalent to a 1% error as 0.01 is 1% of 1), and these weights will fill easily into the test tube for a successful experiment. The crucible will be heated strongly on roaring flame for approximately five minutes and stirred to give all the copper access to the air, until when the solid appears to have turned black. After heating the crucible must be weighed, and then the heating repeated until the crucible has constant mass to show that the copper is fully oxidized. DIAGRAM ...read more.

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