Galvanic cells standard cell potential

C (298.15 K) and 1 bar. standard cell potential See standard emf. standard emf ( °) The emf when the concentration of each solute taking part in the cell reaction is 1 mol-L 1 (strictly, unit activity) and all the gases are at 1 bar. The standard emf of a galvanic cell is the difference between its two standard potentials E° = E°(cathode) — °(anode). 

Since the standard cell potential is for a galvanic cell, it must be a positive... 

The standard cell potential for a galvanic cell is a positive value, E° > 0. 

Calculate the standard cell potential for the galvanic cell in which the following reaction occurs. 

Write the two half-reactions for the following redox reaction. Subtract the two reduction potentials to find the standard cell potential for a galvanic cell in which this reaction occurs. 

In this chapter we have seen that the standard reaction free energy is related to the standard cell potential of a galvanic cell by... 

Predict the standard cell potential and calculate the standard free energy for the following galvanic cells (the standard potentials of these cells were obtained in Exercise 12.19). 

What half-reactions take place at the electrodes in each cell What is the standard cell potential in each case Which electrode is negative Would the cell operate electrolytically or galvanically in carrying out a net reaction from left to right Be sure your decisions accord with chemical intuition. 

To determine the standard cell potential for a redox reaction, the standard reduction potential is added to the standard oxidation potential. What must be true about this sum if the cell is to be spontaneous (produce a galvanic cell) Standard reduction and oxidation potentials are intensive. What does this mean Summarize how line notation is used to describe galvanic cells. 

Looking back at our cell in Fig. 15.2, with the Zn half-cell as the anode and the Cu half-cell as the cathode, we can calculate the standard cell potential for this galvanic cell. In the spontaneous reaction, Zn is oxidized and Cu is reduced, therefore Zn is the anode and Cu is the cathode. 

If the ionic strength of the saturated salt solution is sufficiently low (i.e., the solubihty is sufficiently low), it may be practical to evaluate the solubility product with Eq. 12.5.26 and an estimate of y from the Debye-Hiickel hmiting law (see Prob. 12.19). The most accurate method of measuring a solubility product, however, is through the standard cell potential of an appropriate galvanic cell (Sec. 14.3.3). 

The standard cell potential gq of a cell reaction is the equilibrium cell potential of the hypothetical galvanic cell in which each reactant and product of the cell reaction is in its standard state and there is no Uquid junction potential. The value of for a... 

The potentials of the metals in their 1 mol U salt solution are all related to the standard or normal hydrogen electrode (NHE). For the measurement, the hydrogen half-cell is combined with another half-cell to form a galvanic cell. The measured voltage is called the normal potential or standard electrode potential, E° of the metal. If the metals are ranked according to their normal potentials, the resulting order is called the electrochemi-... 

A problem with compiling a list of standard potentials is that we know only the overall emf of the cell, not the contribution of a single electrode. A voltmeter placed between the two electrodes of a galvanic cell measures the difference of their potentials, not the individual values. To provide numerical values for individual standard potentials, we arbitrarily set the standard potential of one particular electrode, the hydrogen electrode, equal to zero at all temperatures ... 

A student was given a standard Fe(s) Fe2+(aq) half-cell and another half-cell containing an unknown metal M immersed in 1.00 M MNO,(aq). When these two half-cells were connected at 25°C, the complete cell functioned as a galvanic cell with E = +1.24 V. The reaction was allowed to continue overnight and the two electrodes were weighed. The iron electrode was found to be lighter and the unknown metal electrode was heavier. What is the standard potential of the unknown MT/M couple ... 

Lithium metal had few uses until after World War II, when thermonuclear weapons were developed (see Section 17.11). This application has had an effect on the molar mass of lithium. Because only lithium-6 could be used in these weapons, the proportion of lithium-7 and, as a result, the molar mass of commercially available lithium has increased. A growing application of lithium is in the rechargeable lithium-ion battery. Because lithium has the most negative standard potential of all the elements, it can produce a high potential when used in a galvanic cell. Furthermore, because lithium has such a low density, lithium-ion batteries are light. 

The zinc-copper galvanic cell is under standard conditions when the concentration of each ion is 1.00 M, as shown in Figure 19-13. The cell potential under these conditions can be determined by connecting the electrodes to a voltmeter. The measured potential is 1.10 V, with the Zn electrode at the higher (more negative) potential, so Zn gives up electrons and E eii = 1.10 V ... 

In any galvanic cell that is under standard conditions, electrons are produced by the half-reaction with the more negative standard reduction potential and consumed by the half-reaction with the more positive standard reduction potential. In other words, the half-reaction with the more negative E ° value occurs as the oxidation, and the half-reaction with the more positive E ° value occurs as the reduction. Figure 19-15 summarizes the conventions used to describe galvanic cells. 

Combining these features gives an equation that summarizes the calculation of the standard potential for a galvanic cell E i-gjj — E cathode " anode... 

The overall voltage generated by a standard galvanic cell is always obtained by subtracting one standard reduction potential from the other in the way that gives a positive value for E (.gH Example applies this reasoning to zinc and iron. 

A galvanic cell can be constmcted from a zinc electrode immersed in a solution of zinc sulfate and an iron electrode immersed in a solution of iron(II) sulfate. What is the standard potential of this cell, and what is its spontaneous direction under standard conditions ... 

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. 

Equation expresses an important link between two standard quantities. The equation lets us calculate standard electrical potentials from tabulated values for standard free energies. Equally important, accurate potential measurements on galvanic cells yield experimental values for standard potentials that can be used to calculate standard free energy changes for reactions. 

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