For electrolysis, you must know the 4 state symbols:
(s) = solid
(l) = liquid
(g) = gas
(aq) = aqueous solution
When an ionic substance is melted or dissolved in water, the ions are free to move about within the liquid or solution
electrolysis = passing an electric current through ionic substances that are molten or in solution to break them down into elements
During electrolysis, atoms become ions
The positively charged ions move to the negative electrode(Cathode)
The negatively charged ions move to the positive electrode (Anode)
For the atoms to become ions, electrons are either lost (oxidation) or gained (reduction) by the atoms. For you to remember this just use OIL RIG:
O = oxidation
I = is
L = loss (of electrons)
R = reduction
I = is
G = gain (of electrons)
1. The electrodes are made of copper. The impure copper is at the anode (positive electrode) and the pure copper is at the cathode (negative electrode).
2. The copper ions (Cu2+) move from the electrolyte to the cathode (negative electrode) where they then gain 2 electrons (reduction) to form copper.
3. The copper atoms in the impure copper at the anode (positive electrode) lose two electrons (oxidation) to form copper ions (Cu2+). These electrons dissolve in the electrolyte.
4. As the copper ions are released at the positive electrode (anode) the impurities are set free and collect at the bottom.
Purifying Copper Continued...
The reaction at each electrode can be shown using half equations
At the negative electrode (cathode):
Cu2 (aq) + 2e- > Cu (s) (reduction)
At the positive electrode (anode):
Cu (s) > Cu2 (aq) + 2e- (oxidation)
This shows that the purification of copper is a redox reaction as both oxidation and reduction have happened in the same reaction