Chemistry- Electrode potentials and Electrochemical cells.

Question 1

What is a half cell?

Answer 1

A half cell is one of the 2 electrodes in a galvanic cell.
Placing a piece of a reactant in an electrolyte solution makes a half cell.
Twohalf cells combined form an electrochemical cell with a positive and negative terminal.

Question 2

What is the purpose of a salt bridge?

Answer 2

Maintaining a charge balance due to ions being distributed from one half cell to the other.
Electrons do NOT cross over the slat bridge ONLY ions.

Question 3

In a galvanic cell, which electrode favours reduction and oxidation?

Answer 3

• Positive electrode favours REDUCTION.
  eg. Cu^2+ + 2e- —-> Cu
• Negative electrode favours OXIDATION.
  eg. Zn —-> Zn^2+ + 2e-

Question 4

How are electrochemical cells shown/described?

Answer 4

Using Special notation —–> ROOR
Reduced | Oxidised | | Oxidised | Reduced.
eg. Zn | Zn^2+ | | Cu^2+ | Cu

Question 5

What alternative electrode must be used if a half cell is present without a solid metal?

Answer 5

An inert electrode (platinum) must be used if a metal in its elemental state is not present in the half reaction.

Question 6

Why does adding Platinum help?

Answer 6

Finely divided platinum is used in order to increase the surface area.