In my preliminary work I discovered that a large amount of copper nitrate, copper hydroxide and copper carbonate needs to be heated, more than can fit in a test tube, so a large crucible must be used. Also I researched using available books and information that the gas given off copper nitrate, nitrogen dioxide, is toxic, so this must be heated in a fume cupboard.
By weighing the mass of the solid such as copper or copper oxide before and after the experiment, the mass ratio from copper to oxygen can be worked out, and we can see whether constant composition holds true by finding the lowest common mass, with the same ratio being found whichever way you make copper oxide and then make copper. When weighing the mass in my preliminary work, each time the mass was reweighed after being reheated the mass went down, so I discovered that the copper or copper oxide must be reheated and reweighed until a constant mass is achieved. Also using these weights, the formula by working out the ratios of moles can be calculated. This will show the ratio of copper atoms to the ratio of oxygen atoms, indicating the formula. If the ratio is 1:1, the formula is CuO. If the ratio is 2:1, the formula is Cu2O. Moles for copper and oxygen are calculated as below:
Mass of element = the amount of moles
Relative Atomic mass
The amount of moles can be compared to work out the ratio of atoms from copper to oxide within the copper oxide. This can be used to check whether the copper oxide maintains a constant formula however it is made.
Safety glasses and aprons are to be worn at all times. As copper nitrate gives off the toxic gas nitrogen dioxide when heated, this must be heated in a fume cupboard.
Results
The results will be clearly laid out a table to clearly show the mass of the apparatus the solid was weighed in, the apparatus mass and the mass of the solid before the experiment and the mass of the solid and the apparatus after the experiment. From this the table should show the mass of copper and oxygen and copper oxide. This table will be set out much like the one below:
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. The substance must maintain the same formula otherwise it is not the same substance that is being created each time. When the molar quantities are calculated, there will be a direct mass ratio of 1:1 as a mass ratio of 2:1 is Cu2O. Any other mass ratio cannot be accommodated as oxygen’s electron configuration is 2,6, and it can only allow for two more electrons, meaning only one copper atom or two copper atoms can bond with it to form a full outer shell.
Method to make copper from black copper oxide
Firstly, the test tube will be weighed accurately. Then different weights of 0.75 grams 0.88 grams, 1 gram, 1.25 grams and 1.5 grams of copper oxide powder (powder for a large surface area for a displacement 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 a rough 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 hydrogen tube will be clamped into position and will hold up the test tube, and while the test tube is being heated, hydrogen will be passed over the copper oxide. To prevent an explosion, the hydrogen that is being used will be lit at the end of the test tube. The will be heated on a blue flame for about five minutes. When the solid has appeared to have fully changed colour from black to golden brown, you can stop heating, but the hydrogen must continue passing over the copper to prevent it oxidising again until it has cooled. Then it must be weighed. The process of heating the solid with hydrogen passing over the solid must continue until you have reached constant mass, which will show that the solid is fully reduced. The equation is:
Copper Oxide + Hydrogen HEAT Copper + water
Any water collecting up on the test tube is heated up an expelled out through the test tube as a gas.
I have tried this method in my preliminary work, which shows that this is an effective method of reducing Copper Oxide to Copper. This will be used to make copper from all the copper oxide made from copper nitrate, copper hydroxide.
DIAGRAM
Creating Copper Oxide from Copper Carbonate, Copper Nitrate and Copper Sulphate
A sufficient amount of the copper compound needs to be placed in a large crucible. A large mass is to be heated to constant mass, so as much of the copper oxide can be taken as required.It should be an excess of 0.75grams 1 gram, 1.25 grams, 1.5 grams and 1.75 grams in turn. Copper nitrate must be heated slowly to boil off the water (as this is a crystal form) before being heated until it is black. 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
