Core Practical: Electrolysis of Copper(II)Sulfate Flashcards
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Why are copper electrodes cleaned with emery paper before their masses are determined?
To remove surface oxide, grease or other impurities.
In the copper sulfate electrolysis practical, what must be done to the cathode before its final mass is measured?
Rinse it with distilled water and dry it before weighing; the increase in mass is the mass of copper deposited.
In the electrolysis of copper sulfate solution with copper electrodes, what happens to the mass of each electrode?
The anode gets smaller (copper atoms are oxidised to ions that go into solution) and the cathode gets larger (copper ions are reduced to copper atoms).
True or false? When copper sulfate solution is electrolysed with copper electrodes, the solution stays the same shade of blue.
True. The same number of copper ions enter the solution at the anode as leave it at the cathode, so the concentration of does not change.
What is produced at each electrode when copper sulfate solution is electrolysed with inert electrodes?
Copper at the cathode (copper is less reactive than hydrogen) and oxygen at the anode (no halide ions are present).
When copper is purified by electrolysis, what happens to the impurities in the impure copper anode?
As the anode dissolves, insoluble impurities are released and fall to the bottom of the cell, where they collect as a sludge.