C3.4 Flashcards
Component needed for electrolysis
Electrolyte - compound in liquid state which contains mobile ions and can conduct electricity
Two electrodes - carbon and graphite (conduct electricity to electrolyte)
Electrical power supply
Two electrodes?
Positive electrode - anode (attracts negative ions - anions)
Negative electrode - cathode (attracts positive ions - cations)
How does electrolysis of molten salts work?
Ions move to oppositely charged electrodes and become discharged - concentration of ions at electrodes decreases (as they become atoms) and they are replaced by the electrolyte through diffusion - that’s why they need to be in mobile state
Why are inert electrodes used?
So that they do not react with the electrolyte (made from copper or graphite and used in the electrolysis of solutions)
Electrolysis of water
Cathode : 2H+ + 2e- -> H2 (reduction)
Anode : 4OH- -> 2H20 + O2 + 4e-
Conditions for electrolysis of solutions
Cathode - either attract the possible cation in solution or hydrogen. THE LEAST REACTIVE ELEMENT. IS THE ONE THAT IS CREATED AT CATHODE
Anode - either attracts the anion in the solution or oxygen. IF IT IS GROUP 7 IONS, THEN THEY ARE PRODUCED
Components of electroplating
Cathode - object/jewellery you want to coat
Anode - metal you want to coat the cathode with
Electrolyte - solution containing ions of the coating metal
How does electroplating work?
Metal ions in electrolyte are discharged on the surface of the cathode - these ions are replaced by ions leaving the anode until all the metal leaves the anode and is deposited at the cathode.
Anode - Ag(s) -> Ag+(aq) + e-
Cathode - Ag+ +e- -> Ag(s)
How is copper purified?
Both electrodes contain copper - anode is impure copper and cathode is very pure copper. Electrolyte is normally copper sulfate - copper ions are discharged at cathode and this increases in mass (while the anode loses copper atoms and decreases in mass) - impurities fall from the anode and collect underneath
