BRAINCAKEThe Standard Hydrogen Half Cell
The potential of a single half cell cannot be measured on its own. Only a potential difference between two half cells can be measured, so every half cell is compared with the same reference standard, the standard hydrogen half cell (standard hydrogen electrode). Its standard electrode potential is defined as exactly 0.00 V.
The standard hydrogen half cell is made of hydrogen gas at 100 kPa bubbling over a platinum electrode dipped in a solution of H+(aq) ions at 1.00 moldm-3 (for example 1.00 moldm-3 HCl(aq)), at 298 K. The half equation is 2H+(aq) + 2e- &rlhar H2(g).
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Key terms in this lesson
- standard electrode potential
- The e.m.f. of a half cell compared with a standard hydrogen half cell, measured under standard conditions.
- half cell
- A system consisting of an element in two different oxidation states, in which an equilibrium is set up between the two forms.
- salt bridge
- A piece of filter paper soaked in an ionic solution that completes the circuit of an electrochemical cell without reacting with the solutions in the half cells.
More in Electrochemistry
- Oxidation and Reduction
- Ionic Equations
- Electrochemical Half Cells
- Electrochemical Cells
- Standard Electrode Potential Eθ and the Electrochemical Series
- Calomel Electrode
- Standard Cell Potentials Eθcell Values and Electrochemical Cells
- Non-Standard Conditions
All 14 lessons in Electrochemistry · All OCR A-level Chemistry topics