R3.2 (Electrolysis/voltaic cells)

What reaction occurs at the Cathode?

Reduction

What reaction occurs at the Anode?

Oxidation

What direction do electrons flow in electrolysis and voltaic cells?

Anode → Cathode

Charge of Cathode (Electrolysis)

-

Charge of Anode (Electrolysis)

+

Charge of Cathode (Voltaic cell)

+

Charge of Anode (Voltaic cell)

-

Function of salt bridge in voltaic cells

Allow ions to flow between half-cells to balance the charge and complete the circuit

Where do cations flow towards?

Cathode

Where do anions flow towards?

Anode

Which electrochemical cells are reversible?

Secondary cells

Examples of secondary cells

Lead-acid and lithium-ion batteries

Advantages of Lead-acid batteries

Easy to manufacture, low cost and low self-discharge rates

Disadvantages of Lead-Acid Batteries

Lead is toxic, and overcharging produces hydrogen gas, which is an explosion risk.

Advantages of lithium-ion batteries

High energy density and low discharge rates

Disadvantages of lithium-ion batteries

Explosion risk and difficult to extinguish lithium fires

Energy change in electrolytic cell

Electrical to chemical

Energy change of voltaic cell

Chemical to electrical

Spontaneity of electrolytic cell

non-spontaneous

Spontaneity of voltaic cell

Spontaneous