Types of half-cell

Overview

Metal–metal ion half-cell, gas–ion half-cell and ion–ion half-cell.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is a half-cell?

   Model answer

   One half of an electrochemical cell, consisting of an element and its ions in contact, at which either oxidation or reduction occurs.

2. 2

   Describe a metal–metal ion half-cell.

   Model answer

   A strip of the metal dipping into a solution of its own ions at 1.00 mol dm⁻³, as zinc in zinc sulfate solution.

3. 3

   Write the equilibrium for a zinc half-cell.

   Model answer

   Zn²⁺(aq) + 2e⁻ ⇌ Zn(s).

4. 4

   Why is the equilibrium always written as a reduction?

   Model answer

   Tabulated values are all reduction potentials, so writing every half-cell the same way lets them be compared directly.

5. 5

   Describe a gas–ion half-cell.

   Model answer

   The gas is bubbled at 100 kPa over an inert platinum electrode dipping into a solution of the corresponding ions at 1.00 mol dm⁻³.

6. 6

   Give an example of a gas–ion half-cell other than hydrogen.

   Model answer

   Chlorine bubbled over platinum in chloride solution, for the Cl₂/Cl⁻ equilibrium.

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Six ways to work the same material.