From the Electrolysis of concentrated copper(ii) sulphate using carbon electrodes, what product will I get ?

1 Answer
Jul 10, 2017

You will get oxygen and metallic copper.

Explanation:

You have a mixture of "Cu"^"2+", "SO"_4^"2-", and "H"_2"O".

Something must be oxidized, and something must be reduced, so you consult a table of standard reduction potentials like the one below to find suitable candidates,

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The only candidate for reduction in the table is

"Cu"^"2+""(aq)" + 2"e"^"-" → "Cu(s)"; "+0.34 V"

Now,we look for candidates for oxidation.

"Cu"^"2+" and "SO"_4^"2-" are already in their highest oxidation states, so the only candidate for oxidation is water.

We see two possibilities in the table:

"H"_2"O"_2"(aq)" + 2"H"^"+""(aq)" + 2"e"^"-" → 2"H"_2"O"(l); "+1.77 V"
"O"_2"(g)" + 4"H"^"+""(aq)" + 4"e"^"-" → 2"H"_2"O(l)";color(white)(mm) "+1.23 V"

The reaction that requires the least voltage is the formation of oxygen.

Thus the electrolytic cell half-reactions are:

color(white)(mmmmmmmmmmmmmmmmmmmmmmmmmmmmm)ul(E^@"/V")
2×["Cu"^"2+""(aq)" + 2"e"^"-" → "Cu(s)"];color(white)(mmmmmmmmmmmm) "+0.34"
1×[2"H"_2"O(l)" → "O"_2"(g)" + 4"H"^"+""(aq)" + 4"e"^"-"] ;color(white)(mmmmmmmm) "-1.23"
color(white)(mm)"2Cu"^"2+""(aq)" + 2"H"_2"O""(l)" → "2Cu(s)" + "O"_2"(g)" + 4"H"^"+""(aq)"; "-0.89"

Thus, if you electrolyze a solution of "CuSO"_4 using graphite electrodes, you will see metallic carbon being deposited at the cathode and bubbles of oxygen released at the anode

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