Standard Electrode Potentials: The Hydrogen Half-Cell as a Reference
The Hydrogen Half-Cell: Definition and Setup
- The hydrogen half-cell is a simple yet essential electrochemical system.
- It is represented by the following half-equation:
$$
\text{H}^+ (aq) + e^- \leftrightarrow \frac{1}{2} \text{H}_2 (g)
$$
Key Components of the Hydrogen Half-Cell
- Hydrogen Ions ($\text{H}^+$):
- These are present in an aqueous solution, typically at a concentration of $1.00 \, \text{mol dm}^{-3}$ to meet standard conditions.
- Hydrogen Gas ($\text{H}_2$):
- Pure hydrogen gas is bubbled through the solution at a pressure of $1.00 \, \text{atm}$.
- Platinum Electrode:
- A platinum electrode, often coated with platinum black, serves as an inert surface for the redox reaction.
Platinum is used because it is chemically unreactive and provides a conductive surface for electron transfer.
Standard Conditions for the Hydrogen Half-Cell
To ensure consistency, the hydrogen half-cell operates under standard conditions:
- Concentration of $\text{H}^+$ ions: $1.00 \, \text{mol dm}^{-3}$
- Pressure of $\text{H}_2$ gas: $1.00 \, \text{atm}$
