1) The picture on the right shows the copper recovered from the filter paper. White deposits are seen on the surface. Explain how these crystals came about and how can they influence the result?
2) The copper obtained at the end appears to have a greater volume than the original. Why?
Do we have more copper at the end? Explain.
3) What percentage of the original mass of copper was obtained?
4) If the percentage of copper recovered was not 100% suggest at what step the copper might have been lost and provide a reason.
5) After adding zinc to the blue solution of copper sulfate in step E Jonathon was ready to filter the solid copper that was formed. A picture of his beaker is shown on the right.
a) Will the percentage of copper recovered by Jonathon be less than, more than or equal to 100%? Explain.
b) What would you advise Jonathon to do?
6) Suggest what effect the following would have on the percentage of copper recovered and give a reason.
a) The water decanted from the copper oxide had a dark appearance as shown on the right.
b) The copper when filtered in step E was not washed with water.
c) Not all the copper was washed from the beaker during step E.
d) Zinc metal was left unreacted in step E .
e) Not enough zinc was added during step E.
f) Step E was conducted on Friday and the copper recovered was left to dry over the weekend. Some of the copper reacted with oxygen in the air to form copper oxide.
g) Jonathon used 10 mL of nitric acid in step A rather than the prescribed 15mL.
h) Jonathon used 20 mL of nitric acid in step A rather than the prescribed 15mL.
i) The copper recovered in step E was washed 6 times with distilled water rather than the prescribed 3 times.
j) The copper recovered during step E was deposited very quickly and therefore occupied a greater volume than the original sample of copper that we started with.
