Copper And Calorimetry Lab Results

Aim:

The aim of this experiment is to convert copper metal through a series of intermediate copper compounds back into copper metal. By weighing the copper at the beginning and at the end of the experiment the percentage yield can be determined.

Method:

The experiment was carried out as outlined in the practical manual.

Results:

Table: showing masses:

Mass copper wire
0.2510
Mass crucible
28.9257
Mass watch glass
19.6213
Mass watch glass + copper
19.7890
Mass copper product
0.1677

Calculations:

Percentage yield:

Discussion and conclusion:

The percentage yield of copper was calculated to be reasons for such a low yield could be from a few factors such as not all the copper setteling to
the bottom of the beaker before decanting the supernatant liquid thus loosing some yield. I was not able to leave my copper sample in the crucible to dry, as time did not permit so I had to change it from the crucible to the watch glass. Some of the copper may have been lost there. Some of the copper precipitate was lost when transferring it from the beaker to the crucible. As it was hard to make sure all the copper precipitate left the beaker. From this experiment I have learnt that you can perform a whole load of experiment on “something” such as copper just to end up with that “something” copper in another form. While this procedure happens mass is “lost” (when decanting, or reactions are taking place) from the original sample. It will be hard to achieve a 100% yield in this experiment.

Questions:

1. Boiling chips contain many microscopic pours, which provide a rough surface upon which boiling bubbles can form. If there was no surface for these bubbles to form superheating can occur which can ruin your experiment and can become a danger.
2. The aluminum is higher up on the reactivity table than copper and is therefore more reactive and can displace the copper from the solution by reducing the copper ions to copper solid. Any other metal that is higher up on the activity table can be used in place of aluminum, such as sodium. [1] xxx
3. Becoming familiar with basic laboratory procedures and a greater understanding of percentage yield was gained. I leant how to decant properly. How to drain a sample using a crucible, and how efficient one should be when performing procedures to maximize the final yield. [1]

4.

5.
Some precipitate may have been lost when the supernatant liquid was decanted which can result in a yield of less than 100%. Yield may have also been lost when transferring the sample from the beaker into the crucible.
6. This occurs when reactions are not allowed to finish resulting in some of the unwanted precipitate remaining behind. The unwanted precipitate will not precipitate in the subsequent reactions. If the final copper sample is not dry before you weight it could weigh more than 100%
7. Copper sample is brown/red in colour. The copper provided was a shiny brassie colour. This is because the copper provided was in form of a wire. It had undergone further processing. And my final copper sample may have picked up impurities along the way, which made it darker in colour.
8. Acetone is a flammable ketone. If exposed to temperatures greater than its flash point it may explode or cause flash fire.
9. The yield would be more than a 100%, the calculated yield would be incorrect and not a true reflection of actual yield.
10. Because you are adding concentrated nitric acid to a piece of copper. A reaction takes place and gas (NO2 ) is released. [5-10 makes =1 ]
11. Moles of copper wire:
[2]

= 3.39575*10-3

For max CuO all Cu in CuO must come from Cu wire:
Moles of CuO=3.39575*10-3
Mass = 3.39575*10-3x (63.55 +16)
Mass = 0.2701

References:

http://heartmagic.com/zzBoilingPoints.html
http://www.yaksic.com/crcpy6.html