Topic 9: Redox Processes Flashcards
Electrolysis is used in the electroplating of metals. The same amount of current is passed through separate aqueous solutions of
NiSO4, Sn(SO₄)₂ and Cr₂(SO₄)₃ in separate electrolytic cells for the same amount of time. State and explain which cell would deposit the greatest amount (in mol) of metal. Identify the electrode at which the metal is deposited.
Nickel (Ni²⁺) needs only 2 electrons to become metal.
That means you get more moles of Ni compared to the others when the same electricity is used.
What factors affect the the amount of metal deposited during electroplating?
Current, time and concentration
Define standard electrode potential.
The potential difference obtained when a half-cell is connected to a standard hydrogen electrode under standard conditions.
What color does potassium dichromate turn from and into after being reduced?
Orange to green.
Why must the oxidation of ethanol by acidified dichromate be carried out under acidic conditions?
Acidic conditions provide H⁺ ions needed for the reduction of dichromate (Cr₂O₇²⁻) to Cr³⁺.
Why is it very difficult to obtain sodium from sodium chloride by any other method other than molten electrolysis?
Sodium is too reactive to be extracted by chemical reduction because it will need a an even stronger reducing agent to give it electrons for its reduction.
Only electrolysis provides enough energy to reduce Na⁺ to sodium metal.
Explain why an aqueous solution of sodium chloride cannot be used to obtain sodium metal by electrolysis.
REMEMBER THIS IS AQUEOUS ELECTROLYSIS.
In aqueous NaCl, water is present, and water is reduced more easily than Na⁺.
So during electrolysis, hydrogen gas is produced at the cathode instead of sodium metal.
