Question

Describe the Standard Hydrogen Electrode (SHE) with a labeled diagram and its cell reaction.

Hint:

SHE is always written on the left side when used as a reference electrode, and all standard electrode potentials are measured relative to it.

Answer 1

Concept: The Standard Hydrogen Electrode (SHE) is used as a universal reference electrode to measure electrode potentials. Its standard electrode potential is defined as zero volts under standard conditions.
Construction of SHE:
A platinum electrode coated with platinum black is used.
The electrode is immersed in a solution containing \(1\,M\) hydrogen ions (usually acid).
Pure hydrogen gas is bubbled over the platinum surface at 1 atm pressure.
Temperature is maintained at \(25^\circ C\) (298 K).

Labeled Diagram (Text Representation): \[ \text{H}_2(g, 1\,\text{atm}) \;|\; H^+(aq, 1\,M) \;|\; \text{Pt (electrode)} \] Parts:
Platinum electrode (inert conductor)
Acidic solution providing \(H^+\)
Hydrogen gas inlet

Cell Reaction of SHE: SHE can act as anode or cathode depending on the other electrode. Half-cell reaction: \[ 2H^+(aq) + 2e^- \rightleftharpoons H_2(g) \]
Key Features:
Standard electrode potential = \(0.00\,V\)
Reversible electrode
Used to determine electrode potentials of other half-cells