Fig. 1 shows a refinery line used by a cable manufacturer. Copper stripped from old motors is not pure enough for new electrical wire because it contains ca...
Question 1 Report
Fig. 1 shows a refinery line used by a cable manufacturer. Copper stripped from old motors is not pure enough for new electrical wire because it contains carbon and small amounts of other metals. The refinery uses electrolysis to transfer copper from a thick impure sheet to a thin sheet of pure copper. Insoluble material is collected from the bottom of the tank for further processing.
Fig. 1
(a) Give the electrode name for the impure copper sheet. [1]
(b) Use the word oxidation to describe the change to copper atoms at the impure sheet. [2]
(c) Give the half-equation for the change at the pure copper sheet. [2]
(d) Describe what happens to carbon during the process. [1]
(e) Use the properties of copper to give two reasons why pure copper is suitable for electrical cable. [2]
(f) Describe how the mass of each copper sheet changes while the cell operates. [1]
Answer Details
Electrorefining copper
- (a) The impure copper sheet is the anode, the positive electrode. [1]
- (b) Copper atoms at the impure sheet undergo oxidation: they lose electrons and form Cu2+ ions in solution. [2]
- (c) At the pure copper sheet, copper ions are reduced: \[\mathrm{Cu^{2+} + 2e^- \rightarrow Cu}\] [2]
- (d) Carbon does not dissolve. It settles at the bottom as anode sludge. [1]
- (e) Pure copper is suitable for cable because it conducts electricity well and is ductile, so it can be drawn into wires. Low resistance and corrosion resistance are also acceptable. [2]
- (f) The impure copper sheet decreases in mass, while the pure copper sheet increases in mass. [1]
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