Electromotive force of cells

The actual ISE system consists of internal reference electrode 2, internal solution of the ion-selective electrode 2 and the membrane. This system is immersed in andysed solution (analyte) 1, in which reference electrode 1 is also immersed, usually connected through a liquid bridge. The electromotive force of cell (3.1.1) is... 

For converting data on the electromotive force of cells, the value of the Faraday constant has been taken as equal to 23.066 kilocalories per international volt-equivalent. 

Pb (solid, stick form). From data on the electromotive force of cells involving lead in both the crystalline and the stick form, Gerke1 found for the transition from the former to the latter Q = —0.07. 

LiHgaa (Hq.). Lewis and Keyes2 computed the partial molal heat of solution of Li (c) in LiHggg (liq.) from the temperature coefficient of the electromotive force of cells. 

The activity a2 of an electrolyte can be derived from the difference in behavior of real solutions and ideal solutions. For this purpose measurements are made of electromotive forces of cells, depression of freezing points, elevation of boiling points, solubility of electrolytes in mixed solutions and other characteristic properties of solutions. From the value of a2 thus determined the mean activity a+ is calculated using the equation (V-38) whereupon by application of the analytical concentration the activity coefficient is finally determined. The activity coefficients for sufficiently diluted solutions can also be calculated directly on the basis of the Debye-Hiickel theory, which will bo explained later on. 

The bridge solvent Sb may be either S or S" or any other solvent which supports the intention to reduce the voltage contribution of the liquid junctions between the electrode compartments. Tetraethylammonium picrate (TEA PIC) was chosen because the ions are bulky and preferential solvation may be neglected. The mobilities of TEA" and PIC" are very similar in a variety of solvents The electromotive force of cell (B) is given, following Scatchard ... 

The electromotive force of cell (Eq. 5), corrected for the liquid junction potential, E lj, is simply related to the free energy of transfer, AG(p of ion M" from solvent Si to S2 ... 

Measurements of the electromotive force of cells may be used conversely to determine equilibria which are not otherwise amenable to experiment. This method is very frequently employed. The thermodynamical relationship between the electromotive force and the equilibrium constant is often a very convenient means of determining equilibria which cannot be investigated directly at low temperatures owing to the slow rate at which the reactions proceed. As we have seen in the case of the hydrogen-oxygen cell, this method is only applicable when the... 

Table II. Electromotive Force of Cell A from 3 to 35 C Solutions in Seawater I...

The quantity q was obtained by measuring the electromotive force of cells containing standard solutions. The hydrogen ion concentration in these standard solutions was determined from conductance data, using the Arrhenius theory. Sorenson found the value... 

H. Harned and W. Hamer, The ionization constant of water and the dissociation of water in potassium chloride solutions from electromotive forces of cells without liquid junction, JACS, 1933, 55, 2194 2205. 

Hamed HS and Hamer WJ, The ionization constant of water and the dissociation of water in potassium chloride solutions from electromotive forces of cells widiout liquid junction, JACS, 55, 2194-2205 (1933). NB See also Hamed HS and Robinson RA, Temperature variation of die ionization constants of weak electrolytes, Trans. Farad. Soc., 36,973-978 (1940) Ramette RW, On deducing die pK-temperature equation, /. Chem. Edn., 54(5), 280-283 (1977). For pK values as a function of temperature, see Introductory text. Section 2.2.3. 

The conductivities are slightly smaller when the gelatine is set than when it is liquid. The electromotive force of cells with Ag O-l -AgNOs, lOilT-NHiNOs, x Ag, is 0-1483 volt when a is a sat. soln. of Ag2Cr04 0-1469 volt with the same soln. with O-OlNaNOs and 0-2247 volt with the salt. soln. of silver chromate plus 0-l -K2CrO4. 

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