Search results
Results from the WOW.Com Content Network
For example, from Fe 2+ + 2 e − ⇌ Fe(s) (–0.44 V), the energy to form one neutral atom of Fe(s) from one Fe 2+ ion and two electrons is 2 × 0.44 eV = 0.88 eV, or 84 907 J/(mol e −). That value is also the standard formation energy (∆ G f °) for an Fe 2+ ion, since e − and Fe( s ) both have zero formation energy.
Bipolar electrochemistry scheme. In electrochemistry, standard electrode potential, or , is a measure of the reducing power of any element or compound.The IUPAC "Gold Book" defines it as; "the value of the standard emf (electromotive force) of a cell in which molecular hydrogen under standard pressure is oxidized to solvated protons at the left-hand electrode".
To avoid possible ambiguities, the electrode potential thus defined can also be referred to as Gibbs–Stockholm electrode potential. In both conventions, the standard hydrogen electrode is defined to have a potential of 0 V. Both conventions also agree on the sign of E for a half-cell reaction when it is written as a reduction.
The absolute potential of the SHE is 4.44 ± 0.02 V at 25 °C. Therefore, for any electrode at 25 °C: = + where: E is electrode potential V is the unit volt M denotes the electrode made of metal M (abs) denotes the absolute potential
The difference can be measured as a difference in voltage potential: the less noble metal is the one with a lower (that is, more negative) electrode potential than the nobler one, and will function as the anode (electron or anion attractor) within the electrolyte device functioning as described above (a galvanic cell).
For example, for oxygen, the species would be in the order O 2 (0), H 2 O 2 (–1), H 2 O (-2): The arrow between O 2 and H 2 O 2 has a value +0.68 V over it, it indicates that the standard electrode potential for the reaction: O 2 (g) + 2 H + + 2 e − ⇄ H 2 O 2 (aq) is 0.68 volts.
E pzc = E − E σ=0. where: E pzc is the electrode potential difference with respect to the point of zero charge, E σ=0; E is the potential of the same electrode against a defined reference electrode in volts; E σ=0 is the potential of the same electrode when the surface charge is zero, in the absence of specific adsorption other than that ...
The standard electrode potential E 0 against standard hydrogen electrode (SHE) is 0.230 V ± 10 mV. [citation needed] The potential is however very sensitive to traces of bromide ions which make it more negative. The more exact standard potential given by an IUPAC review paper is +0.22249 V, with a standard deviation of 0.13 mV at 25 °C. [2]