Electromotive force standard equilibrium potential

The electromotive force of this cell is equivalent to the redox potential Fe2. of the reaction referred to the standard hydrogen electrode, i.e. the equilibrium potential of the redox reaction, and it is given by Eq. 9.33 at the standard temperature and pressure ... 

The reduction potential is an electrochemical concept. Consider a substance that can exist in an oxidized form X and a reduced form X . Such a pair is called a redox couple. The reduction potential of this couple can be determined by measuring the electromotive force generated by a sample half-cell connected to a standard reference half-cell (Figure 18.6). The sample half-cell consists of an electrode immersed in a solution of 1 M oxidant (X) and 1 M reductant (X ). The standard reference half-cell consists of an electrode immersed in a 1 M H+ solution that is in equilibrium with H2 gas at 1 atmosphere pressure. The electrodes are connected to a voltmeter, and an agar bridge establishes electrical continuity between the half-cells. Electrons then flow from one half-cell to the other. If the reaction proceeds in the direction... 

The standard reduction potential Eq can be defined as the electromotive force (in volts) measured in a half-cell containing 1 M oxidant and 1 M reductant at 25 °C and pH 7.0, in equilibrium with a reference half-cell which can accept the electrons. 

The oxidation-reduction potentials for half reactions such as Fe" —> Fe + e are measured by putting a piece of platinum or other inert metal into a solution containing ferrous and ferric ions in standard concentrations, and combining this half cell with the standard hydrogen half cell. Again, the platinum serves to conduct electrons and to catalyze the equilibrium between ferrous and ferric ions. The electromotive force of the cell... 

For biological systems this tendency is expressed by the standard reduction potential, Eq, defined as the electromotive force (emf) in volts given by a half-cell in which the reductant and oxidant species are both present at 1.0 M concentration unit activity, at 25°C and pH 7.0 in equilibrium with an electrode which can reversibly accept electrons from the reductant species, according to the equation ... 

The potential difference is closely related to the difference of the electrochemical potential based on the electrochemical affinity. If we could measure A(p directly, we could organize the table of electromotive forces based on the Galvani potential difference. However, A

reference electrode to measure the half cell potential at an electrode. When a certain electrcxle is coupled with a reference electrode, then the electromotive force can be measured. Since we usually use some reference electrodes as standards, the electromotive force is defined as the equilibrium potential of the reaction. The table was made in such a way and the hydrogen reference electrode was used to measure and calculate potentials for the half cell reactions. 

Recall that MiSO iaq) and M2SOi aq) are in their ionic state in solution (aqueous). Both metals are externally connected to a electrical circuit in order to measure the potential difference between them. In other words, the circuit is used to measure the galvanic cell potential by a voltmeter (V). This measurable oeU potential is current/iesistance dependent. If current ceases to flow, then the cell potential is known as the open-circuit potential or standard potential (E°), which are illustrated in Figure 2.2 for pure metal reduction. The standard potential is also known as the electromotive force (emf) under equilibrium conditions unit activity, 25 °C, and 1 atm (101 kPa) pressure. 

A power supply may generate a potential difference that perfectly counterbalances that existing between the two electrodes. In these conditions, no current flows. The situation is equivalent to that encountered when the two electrodes are not connected. We say that the system is at equilibrium. Sometimes, the potential difference E determined at equilibrium (the zero-current cell potential) is still called the electromotive force of the cell. In the case of a chemically reversible cell, it is endowed with a very well-determined meaning (see Chap. 2 and later in this chapter) It permits us to obtain the standard electrode potentials. Establishing the latter is in the realm of the application of Nernst s law. 

Electrode Potential, Equilibrium Electrode Potential, Standard Electrode Potential, Electromotive Force... 

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