Mį¶»āŗ + z eā» ā M(s)z: number dāelectrons per reduced metal ion.
Use when: Cathodic half-equation adapted to the species actually present.
Electrolysis and electrorefining
Distinguish between electrowinning and electrolytic refining.
What is happening?
In electrorefining, an impure metal anode can dissolve while a purer metal is deposited at the cathode. Impurities remain in solution or form sludge; In electrowinning, the metal supply comes mainly from the solution.
The electric charge limits the theoretical mass deposited. Competing reactions consume part of the current; Faradic efficiency and energy efficiency are therefore two different concepts.
The formulas, with their conditions.
m = Ī·F M I t / (z F)m: g if M in g/mol; I: A; t: s; F ā 96,485 C/mol ; Ī·F: faradaic efficiency.
Use when: Deposition of the metal considered, average yield defined over the interval.
Ćnergie = U I tU: V ; I: A; t: s; energy: J.
Use when: Constant power and voltage, otherwise integrate U(t)I(t).
Where is this principle used?
Copper, zinc or nickel refinery
Produce a metal deposit using the appropriate process.
Surface treatment industry
Connect electric charge and deposit, with baths specific to the application.
What to observe in the experiment
Double the time at constant current and efficiency; predict the mass deposited. Then compare a faradic efficiency less than 100%.
References and readings
This sheet explains the principles and their assumptions. Educational simulation can simplify the process; an industrial model requires suitable data and validation.
Have you understood the essentials?
Only one correct answer per question. Answer all three questions, then view the answer key.
Intu Lab Ā· Understanding sheet Ā· Kimba Christian