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Products formed at the anode and cathode? ASAP please!A student is attempting to...

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nerdygirl-1996 | Student, Undergraduate | (Level 1) Honors

Posted November 10, 2012 at 6:49 AM via web

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Products formed at the anode and cathode? ASAP please!

A student is attempting to electroplate a metal key via electrolysis. The experiment is set up as follows:a copper plate is connected to the positive terminal of a battery to act as the anode, a metal key is connected to the negative end acting as the cathode. They are immersed in a solution of coper sulphate in a beaker. Together these elements combine to form an electrolytic cell. Taking water in the solution into consideration, name the substances form at the anode and cathode along with the reactions to produce these substances.

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llltkl | College Teacher | (Level 3) Valedictorian

Posted November 10, 2012 at 8:37 AM (Answer #1)

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Water dissociates to produce H^+ and OH^- ions. CuSO4 also dissociates in solution into Cu^2+ and SO4^2- ions. On passing electricity through the solution, the following changes take place:  

At the Cathode (-ve electrode): reduction occurs, possible candidates to be reduced and their E^0 values are H^+(0.00V) and Cu^2+(+0.34V).

Quite understandably, Cu^2+ ions shall be preferentially discharged over H^+ ions, forming a layer of metallic copper over the key. The cathode reaction will be:

Cu^2+ + 2e -> Cu

At the Anode (+ve electrode): oxidation takes place, possibilities and their E^0 values are OH^-(-0.40V, over platinum electrodes) and SO4^2-(-2.0V) and dissolution of copper plate to produce Cu^ 2+ ions (-0.34V). So dissolution of copper should be preferred. As copper plate is used as anode, its discharge shall be additionally favoured. The anode reaction will be:

Cu -> Cu^2+ + 2e

Sources:

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nerdygirl-1996 | Student, Undergraduate | (Level 1) Honors

Posted November 17, 2012 at 7:52 AM (Answer #2)

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Thankyou

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