Answer to Question #71985 in Physical Chemistry for Ali Rostamnejad

Question

down vote
favorite
I have a question about an electrochemical reaction in an experiment. in a electrolytic cell, we have an aqueous electrolyte includes potassium per sulfate and sodium hydroxide, anode and cathode both are copper surface, after electrochemical reaction, the surface of cathode has got oxide of copper, would you tell me what is the reaction took place in the cell and how the oxide of copper is made on the cathode? its so important for me, please help .

Answer 1

Solution:
Products of electrolytic copper sulfate solution with copper electrodes are copper metals and copper ions (dissolved copper anode).
Using a simple apparatus and two copper electrodes, products of electrolysis of copper sulfate solution are a copper precipitate on a negative cathode electrode, and copper dissolves on a positive anode electrode.
When copper (II) sulfate is electrolyzed with a copper anode electrode (the cathode can be carbon or copper), the copper deposited on the cathode (-) is equal to copper, dissolved in the anode (+). Therefore, the blue color of Cu2 + ions remains constant, since the Cu substrate = Cu is dissolved. Both of them involve two electron transitions, which means that the mass of the deposited Cu = mass of Cu is dissolved at the same amount of flow of current.
Since the cathode is a negatively charged electrode, in the course of electrolysis positively charged particles tend to approach the cathode, in our case the copper (Cu2 +) cations that in solution can be in the form of particles of copper octide CuO.
The cation Cu2+ in the solution binds to the hydroxide-anion, forming a copper hydroxide Cu(OH)2, which is not stable and falls into water and copper oxide:
Cu2+ + OH- = Cu(OH)2;
Cu(OH)2 = CuO + H2O
Therefore, the copper oxide particles settle on the surface of the cathode.