Quick questions on Electrolytic cells and Faraday's laws: VCE Chemistry Unit 3

An electrolytic cell uses an external electrical energy source (a battery or DC power supply) to drive a non-spontaneous redox reaction. The cell consumes electrical energy and produces chemicals (the reverse of a galvanic cell, which produces electrical energy from a spontaneous reaction).

An electrolytic cell has three components:

This is the opposite polarity to a galvanic cell, but in both cells oxidation occurs at the anode and reduction at the cathode. (AN OX, RED CAT still applies.)

Molten electrolysis. Only the cations and anions of the salt itself are present. The cation is reduced at the cathode; the anion is oxidised at the anode.

To calculate the amount of substance produced or consumed:

Only the cations and anions of the salt itself are present. The cation is reduced at the cathode; the anion is oxidised at the anode.

Water (H2O) is also present, and it can be reduced or oxidised in competition with the dissolved ions. To predict the product, compare reduction potentials of all possible reductions at the cathode (and oxidations at the anode), and choose the most likely (typically the species with the most positive reduction potential for cathode reduction, and the most negative reduction potential when reversed for anode oxidation).

In a galvanic cell, the anode is negative and the cathode is positive; in an electrolytic cell, the anode is positive and the cathode is negative. In both cells, oxidation is at the anode and reduction is at the cathode.

Q = It requires t in seconds. Multiply minutes by 60 or hours by 3600.

Each species has its own electron count. Cu^2+ -> Cu needs 2 e^- per atom; Al^3+ -> Al needs 3 e^-; Ag^+ -> Ag needs 1 e^-. Forgetting this is the most common Faraday's-law error.

In aqueous solution, water is reduced at the cathode in preference to Na^+ (which is too far up the series). Molten NaCl gives Na; aqueous gives H2.

Electrolytic cells use a single electrolyte with no salt bridge.

The external power supply provides the energy. An "electrolytic cell with no power source" is not a thing; with no power source it would either do nothing or reverse to behave as a galvanic cell.