Standard potential determination

The relative thermodynamic stability of two complexes can be predicted from a comparison of then-standard potentials. Determine which complex of the following pair is the more stable and state your... 

Standard Potential Determinations Involving Cells with Liquid Junctions, or Equilibrium... 

From the standard potentials, determine the reaction between the following half-reactions, and calculate the corresponding standard cell voltage ... 

As obtained using the standard potentials determined in ref. 27 and the experimental apparent rate constants measured in ref.25. Values in parentheses are previous direct... 

A problem that has fascinated surface chemists is whether, through suitable measurements, one can determine absolute half-cell potentials. If some one standard half-cell potential can be determined on an absolute basis, then all others are known through the table of standard potentials. Thus, if we know E for... 

Another troublesome aspect of the reactivity ratios is the fact that they must be determined and reported as a pair. It would clearly simplify things if it were possible to specify one or two general parameters for each monomer which would correctly represent its contribution to all reactivity ratios. Combined with the analogous parameters for its comonomer, the values rj and t2 could then be evaluated. This situation parallels the standard potential of electrochemical cells which we are able to describe as the sum of potential contributions from each of the electrodes that comprise the cell. With x possible electrodes, there are x(x - l)/2 possible electrode combinations. If x = 50, there are 1225 possible cells, but these can be described by only 50 electrode potentials. A dramatic data reduction is accomplished by this device. Precisely the same proliferation of combinations exists for monomer combinations. It would simplify things if a method were available for data reduction such as that used in electrochemistry. 

Chlorine dioxide gas is a strong oxidizer. The standard reversible potential is determined by the specific reaction chemistry. The standard potential for gaseous CIO2 in aqueous solution reactions where a chloride ion is the product is —1.511 V, but the potential can vary as a function of pH and concentration (26) ... 

For a substance in a given system the chemical potential gi has a definite value however, the standard potentials and activity coefficients have different values in these three equations. Therefore, the selection of a concentration scale in effect determines the standard state. 

Determine E° and reaction spontaneity from standard potentials. 

It must be emphasised that standard electrode potential values relate to an equilibrium condition between the metal electrode and the solution. Potentials determined under, or calculated for, such conditions are often referred to as reversible electrode potentials , and it must be remembered that the Nernst equation is only strictly applicable under such conditions. 

Standard potentials are determined with full consideration of activity effects, and are really limiting values. They are rarely, if ever, observed directly in a potentiometric measurement. In practice, measured potentials determined under defined concentration conditions (formal potentials) are very useful for predicting the possibilities of redox processes. Further details are given in Section 10.90. 

If there are no standard conditions or in the case where it is not be possible to measure the standard potential, the value can be determined by thermodynamic calculations (see Sec. 1.3.2). 

Slow systems the determined Ein does not correspond to the standard potential. Estimated value. 

The electrical double layer at pc-Zn/fyO interfaces has been studied in many works,154 190 613-629 but the situation is somewhat ambiguous and complex. The polycrystalline Zn electrode was found to be ideally polarizable for sufficiently wide negative polarizations.622"627 With pc-Zn/H20, the value of Eg was found at -1.15 V (SCE)615 628 (Table 14). The values of nun are in reasonable agreement with the data of Caswell et al.623,624 Practically the same value of Eff was obtained by the scrape method in NaC104 + HjO solution (pH = 7.0).190 Later it was shown154,259,625,628 that the determination of Eo=0 by direct observation of Emin on C,E curves in dilute surface-inactive electrolyte solutions is not possible in the case of Zn because Zn belongs to the group of metals for which E -o is close to the reversible standard potential in aqueous solution. 

SOLUTION We can determine the standard potential of an electrode by measuring the emf of a standard cell in which the other electrode has a known standard potential and applying Kq. 3. 

In some cases, we find that available tables of data do not contain the standard potential that we need but do contain closely related values for the same element for instance, we might require the standard potential of the Ce4+/Ce couple, whereas we know only the values for the Ce3+/Ce and Ce4+/Ce3+ couples. In such cases, the potential of a couple cannot be determined by adding or subtracting the standard potentials directly. Instead, we calculate the values of AG° for each half-reaction and combine them into the AC° for the desired half-reaction. We then convert that value of AG° into the corresponding standard potential by using Eq. 2. 

Use the information in Appendix 2B to determine the standard potential for the redox couple Ce4"7Ce, for which the reduction half-reaction is... 

The equilibrium constant of a reaction can be calculated from standard potentials by combining the equations for the balf-reactions to give the cell reaction of interest and determining the standard potential of the corresponding cell. 

STRATEGY First, write the balanced equation for the cell reaction and the corresponding expression for Q, and note the value of n. Then determine E° from the standard potentials in Table 12.1 or Appendix 2B. Determine the value of Q for the stated conditions. Calculate the emf by substituting these values into the Nernst equation, Eq. 6. At 25.00°C, RT/1 = 0.025 693 V. 

Determine the standard potential of an electrode from a cell emf (Example 12.5). 

Self-Test 15.3B Write the half-reactions and the overall reaction for the oxidation of water by F2. Determine the standard potential and AG° for the reaction. 

The compound Cr(OH), is very insoluble in water therefore, electrochemical methods must be used to determine its fCsp. Given that the reduction of Cr(OH)3(s) to Cr(s) and hydroxide ions has a standard potential of —1.34 V, calculate the solubility product for Cr(OH)3. 

The standard potential for any galvanic cell is determined by subtracting the more negative standard reduction potential from the more positive standard reduction potential. A positive E ° indicates spontaneity under standard conditions. 

C19-0026. Using standard reduction potentials, determine A G ° and. eq at 25 °C for each of the following reactions ... 

The standard reduction potentials determined in aqueous solution give hierarchies slightly different from the antioxidant hierarchy established in DMF. For the potential determined by pulse radiolysis the ordering according to tendency of regeneration is (Jovanovic et al, 1994) ... 

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