Cell potential calculation

In Table 1.1, the thermodynamic cell potentials calculated for some other organics are given. Values close to 1V can be achieved under standard conditions. Figure 1.1 shows a schematic presentation of a hypothetical fuel cell for the incineration of organic pollutants with co-generation of electrical energy. 

The larger this potential difference is, the greater is the driving force for the reaction. Whether corrosion does occur, and at what rate, is dependent on other factors. For corrosion to occur, there must be a current flow and a completed circuit, which is then governed by Ohm s law I = E/R. The cell potential calculated here represents the peak value for the case of two independent reactions. If the resistance were infinite, the cell potential would remain as calculated but there would be no corrosion at all. The resistance in the circuit is dependent on a number of factors, including the resistivity of the media, surface films, and the metal itself. As current begins to flow, the potentials of both... 

C is correct. The potential given are reduction potentials. Since copper is reduced, we can use its potential (0.15 V) as written. Tin is oxidized, so we have to change the sign before we calculate. The total potential is 0.15 V + 0.14 V = 0.29 V. Notice that we ignore the coefficients when we do cell potential calculations. 

Table 19-1 shows that cell potentials calculated without activity coefficient corrections exhibit significant error. It is also clear from the data in the fifth column of the table that potentials computed with activities agree reasonably well with experiment. 

The potentials, relative to the standard hydrogen electrode, of several half cells used as reference electrodes are given in Table 6.1 (the section Examples of Half-Cell Reactions and Nemst-Equation Calculations in Chapter 2 provides discussions of half-cell-potential calculations). There are a number of factors that contribute to the selection of components and to the design of a satisfactory reference half cell ... 

The difference between the theoretical cell potential (calculated based on the redox reactions that occur at the electrodes and the Nernst equation) and the cell... 

The calculation of cell potential for em/requires only the addition of the cm/values for each half-reaction, while the same cell potential calculation using standard potentials requires the usage of the following convention ... 

Table 7.3 Equilibrium composition for fuel gas and reversible cell potential calculated using the Nernst equation and assuming initial anode gas composition of 77.5% H2/19.4% C02/3.1% H2O at 1 atmosphere and cathode composition of 30% O2, 60% CO2, /10% N2...

Calculate the molar concentration for the underlined component in the following cell if the cell potential is measured at +0.294 V... 

To calculate the open circuit voltage of the lead—acid battery, an accurate value for the standard cell potential, which is consistent with the activity coefficients of sulfuric acid, must also be known. The standard cell potential for the double sulfate reaction is 2.048 V at 25 °C. This value is calculated from the standard electrode potentials for the (Pt)H2 H2S04(yw) PbS04 Pb02(Pt) electrode 1.690 V (14), for the Pb(Hg) PbS04 H2S04(yw) H2(Pt) electrode 0.3526 V (19), and for the Pb Pb2+ Pb(Hg) 0.0057 V (21). 

The three values of ° are easily calculated from half-cell potentials. Then, we can predict with confidence that reaction (65) will not occur to an appreciable extent if solid copper is immersed in dilute acid. The negative value of ° (—0.34 volt) indicates that equilibrium in (65) strongly favors the reactants, not the products. 

H+], calculation of, 192, see also Hydrogen ion Haber, Fritz, 151 Haber process, 140, 150 Hafnium, oxidation number, 414 Haldane, J. B. S., 436 Half-cell potentials effect of concentration, 213 measuring, 210 standard, 210 table of, 211, 452 Half-cell reactions, 201 Half-life, 416 Half-reaction, 201 balancing, 218 potentials, 452 Halides... 

Self-Test 12.12A Calculate the molar concentration of Y1H in a saturated solution of YF3 by using a cell constructed with two yttrium electrodes. The electrolyte in one compartment is 1.0 M Y(NO ),(aq). In the other compartment you have prepared a saturated solution of YF3. The measured cell potential is +0.34 V at 298 K. 

The aluminum-air fuel cell is used as a reserve battery in remote locations. In this cell aluminum reacts with the oxygen in air in basic solution, (a) Write the oxidation and reduction half-reactions for this cell, (b) Calculate the standard cell potential. See Box 12.1. 

Calculate the standard cell potential for the reaction between silicon and water in a cell that also produces hydrogen from water and write the balanced equation for the cell reaction. See Box 12.1. 

The calculation o E° for this cell illustrates an important feature of cell potentials. A standard cell potential is the difference between two standard reduction potentials. This difference does not change when one half-reaction is multiplied by 2 to cancel electrons in the overall redox reaction. 

Atmospheric O2 has a partial pressure of 0.20 bar, and atmospheric water vapor is saturated with carbon dioxide. This dissolved CO2 forms carbonic acid, which generates a hydronium ion concentration of about 2.0 X 10 M. The Nemst equation allows calculation of the half-cell potential for the reduction of 02(g) under these... 

One main advantage of such a power source is the direct transformation of the chemical energy of methanol combustion into electrical energy. Hence, the reversible cell potential, can be calculated from the Gibbs energy change, AG, associated with the overall combustion reaction of methanol (1), by the equation ... 

The EMF of a cell is calculated from the electrode potentials (expressed for both electrodes with respect to the same reference electrode) as the difference of the potentials of these electrodes written on the right and left in the scheme ... 

EXAMPLE 14.5. Calculate the standard cell potential of the Danicll cell, shown in Fig. 14-l. 

Calculation of the internal cell potential is a very complicated matter because the electrochemistry of all of the species within the protocell would have to be balanced subject to their composition quotient Q, after which the standard free energy would have to be established from tabulations. The transport of Na+ would also change this balance, along with the ionic strength of the solution and the stability of the proteins or prebiotic molecules within the protocell. Such non-equilibrium thermodynamics forms the basis of the protocell metabolism. The construction... 

The Nernst equation is used to calculate electrode potentials or cell potentials when the concentrations and partial pressures are other than standard state values. The Nernst equation using both base 10 and natural logarithms is given by ... 

A First we write down the two half-equations, obtain the half-cell potential for each, and then calculate c0ell. From that value, we determine AG°... 

This is a method involving a two-compartment cell with a salt bridge connection and having two identical indicator electrodes. The sample solution is placed in one compartment and a blank solution having the same total ionic strength in the other. Increments of a standard solution of the species to be determined are added to the blank compartment until the cell potential is zero. At this point, the activities of the species of interest in each compartment are equal and that of the sample solution can therefore be calculated. A concentrated standard solution should be used to minimize dilution errors. This method is particularly useful for the determination of trace amounts or where no suitable titrant can be found. 

Calculate the theoretical cell potentials for the following systems ... 

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