Applications of Electrolytic cells- Electroplating & Electro-refining Flashcards
Electrolytic cells convert ____ energy to _____ energy.
electrical
chemical potential energy
The object to be plated must be connected to the ____ (as this is the site of reduction)
cathode
The electrolyte must contain the ions of the ____ to be coated onto the object.
metal
The ____ should be made of the same metal being used to coat the object. This allows for the replacement of the cations in the solution. (an inert anode would also work, but the cation concentration would continuously decrease, affecting the plating process)
anode
What type of metals can this process only be used for?
This process can only be used for metals that are more likely to be reduced than water (i.e., fall below water on the SEP or are better oxidizing agents than water).
Electrolytic cells can be used to ___ unreactive metals from their ores. Most commonly, we see this process used for the refining of Copper metal from blister copper.
refine
Blister copper is used as the ___, while a small bar or pure copper is used as the ____.
The electrolyte is a solution of copper (II) ions, usually CuSO4.
The concentration of the Cu2+ ions will stay largely ____ in the solution as the oxidation and reduction processes occur at a similar rate.
anode
cathode
constant
What type of metals would electrorefining not work for?
This method would not work for a metal that is more reactive than water, for example, aluminium or magnesium, as their ions would not reduce in preference to the water in the solution.
What are less reactive impurities?
Less reactive impurities (e.g., Au and Ag) – these metals are much less likely to be oxidized than Cu (are worse reducing agents/have more positive E0 values/hold onto their electrons more strongly) and so they will not lose their electrons to the external circuit. These atoms will be dislodged from the anode as the copper atoms are oxidized into ions and they will form a sludge beneath the anode.
What are the more reactive impurities?
More reactive metals (e.g., Zn) – These are more likely to be oxidized than Cu and so will readily lose their electrons to form cations in the electrolyte solution. By virtue of their atoms being better reducing agents (i.e., more likely to be oxidized), these ions are worse oxidizing agents than Cu2+ (i.e., they are less likely to gain electrons and be reduced) than Cu2+. These ions will stay in solution and not plate the cathode.
Why is the electrolyte usually made of nitrate?
Nitrates are always soluble.
True or false
Polyatomic ions will never be reduced or oxidised.
True, they will be spectator ions.
Sulphuric acid is often added to the electrolyte solution. Suggest ONE reason for this addition of sulphuric acid
It increases the conductivity of the solution (OR increases the rate of the reaction)
