Full Answer Section

Preparation of a Standard Hydrogen Electrode

To prepare a SHE, the following components are required:

1. Platinum electrode: A platinum foil, coated with platinum black (finely divided platinum), is used as the electrode. Platinum is chosen for its inertness and ability to adsorb hydrogen gas efficiently.

Hydrogen gas: Pure hydrogen gas is bubbled continuously over the platinum electrode.

• Solution of hydrogen ions: A 1.0 M hydrochloric acid (HCl) solution is used to provide a source of hydrogen ions.

Temperature control: The entire setup is maintained at 25°C (298 K).

Pressure: The hydrogen gas is maintained at a pressure of 1 atm.

Steps involved:

1. The platinum electrode coated with platinum black is immersed in a 1.0 M HCl solution.

Pure hydrogen gas is bubbled continuously over the electrode.

The temperature of the system is maintained at 25°C.

The pressure of the hydrogen gas is adjusted to 1 atm.

Under these conditions, the following equilibrium is established at the platinum electrode:

2H⁺(aq) + 2e⁻ ⇌ H₂(g)

The potential of this electrode is defined as 0 volts.

Key points to remember:

• The platinum electrode acts as a catalyst for the hydrogen ion reduction and hydrogen gas oxidation reactions.

The platinum black coating increases the surface area of the electrode, facilitating the adsorption of hydrogen gas.

The SHE is a reversible electrode, meaning it can act as both an anode and a cathode depending on the other electrode in the cell.

Maintaining constant temperature, pressure, and hydrogen ion concentration is crucial for accurate measurements.

By adhering to these conditions, a standard hydrogen electrode can be prepared, providing a reliable reference point for measuring the electrode potentials of other electrochemical systems