Voltaic cells standard cell potential

Voltaic Cells, Standard Cell Potentials, and Direction of Spontaneity... 

Calculate the standard cell potentials (emf) in a voltaic cell whose half-reactions are given below. 

Relating standard cell potential to standard electrode potentials in a voltaic cell (693) ... 

The standard cell potential of a voltaic cell, depends on the particular cathode and anode half-cells. We could, in principle, tabulate the standard cell potentials for all possible cathode/anode combinations. However, it is not necessary to undertake this arduous task. Rather, we can assign a standard potential to each half-cell and then use these half-cell potentials to determine Etea- The cell potential is the difference between two half-cell potentials. By convention, the potential associated with each electrode is chosen to be the potential for reduction at that electrode. Thus, standard half-cell potentials are tabulated for reduction reactions, which means they are standard reduction potentials, denoted Ered- The standard cell potential, ceU> is the standard reduction potential of the cathode reaction, (cathode), minus the standard reduction potential of the anode reaction, (anode) ... 

A FIGURE 20.10 Graphical representation of standard cell potential of a voltaic cell. 

The standard cell potential is 1.46 V for a voltaic cell based on the following half-reactions ... 

Analyze We are given the equation for a redox reaction and asked to use data in Table 20.1 to calculate the standard cell potential for the associated voltaic celL... 

The fact that the standard cell potential is the difference between the standard reduction potentials of cathode and anode is illustrated graphically in M FIGURE 20.10. The more positive E° value identifies the cathode, and the difference between the two standard reduction potentials is the standard cell potential. -4 FIGURE 20.11 shows E values for the two half-reactions in the Zn-Cu voltaic cell of Figure 20.5. 

The standard cell potential of a voltaic cell is the difference between the standard reduction potentials of the half-reactions that occur at the cathode and the anode u = (cathode) — (anode). The value of u is positive for a voltaic ceU. 

Calculate the standard cell potentials of voltaic cells that contain the following pairs of half-cells. Use values from Table 21-1 in your textbook. 

To determine the value of E° for a sfandard electrode such as that to which half-cell reaction (19.6) applies, we compare it with a standard hydrogen electrode (SHE). In this comparison, the SHE is always taken as the electrode on the left of the cell diagram—the anode—and the compared electrode is the electrode on the right—the cathode. In the following voltaic cell, the measured potential difference is 0.340 V, wifh electrons flowing from the H2 to the Cu electrode. 

A voltaic cell converts chemical energy into electrical energy. It consists of two parts called half-cells. When two different metals, one in each half-cell, are used in the voltaic cell, a potential difference is produced. In this experiment, you will measure the potential difference of various combinations of metals used in voltaic cells and compare these values to the values found in the standard reduction potentials table. 

Applying Concepts Write the half-reactions for the anode and cathode in each of the voltaic cells in the data table. Look up the half-reaction potentials from the standard reduction potentials table (Table 21-1) and record these in the data table. 

Understanding voltaic cells, anodes, and cathodes Figuring standard reduction potentials and electromotive force Zapping current into electrolytic cells... 

In a similar though less diabolical manner, the electrons produced at the anode of a voltaic cell have a natural tendency to flow along the circuit to a location with lower potential the cathode. This potential difference between the two electrodes causes the electromotive force, or EMF, of the cell. EMF is also often referred to as the cell potential and is denoted fj.g,. The cell potential varies with temperature and concentration of products and reactants and is measured in volts (V). The standard cell potential, or E° gn, is the that occurs when concentrations of solutions ire all at 1 M and the cell is at standard temperature and pressure (STP). 

A concentration cell is any voltaic cell in which two half-cells consist of identical electrodes with different solution concentrations. For such a cell, its cell potential under standard conditions, 8°g j, is zero. 

A voltaic cell contains one half-cell with a zinc electrode in a Zn2+ (aq) solution and a copper electrode in a Cu2+(aq) solution. At standard condition, E° = 1.10 V. Which condition below would cause the cell potential to be greater than 1.10 V ... 

You have probably worked with tables of standard reduction potentials before. These tables provide the reduction potentials of various substances. It describes an oxidized species s ability to gain electrons in a reduction half-reaction (like copper in the voltaic cell example). According to this definition, we can use a value from the table to represent the E°red in the expression above, but how do you find the E°ox ... 

In a voltaic cell where all ions have a concentration of 1M, the cell potential is equal to the standard potential. For cells in which ion concentrations are greater or less than 1M, as shown below, an adjustment must be made to calculate cell potential. That adjustment is expressed by the Nemst equation ... 

In voltaic cells, it is possible to carry out the oxidation and reduction halfreactions in different places when suitable provision is made for transporting the electrons over a wire from one half-reaction to the other and to transport ions from each half-reaction to the other in order to preserve electrical neutrality. The chemical reaction produces an electric current in the process. Voltaic cells, also called galvanic cells, are introduced in Section 17.1. The tendency for oxidizing agents and reducing agents to react with each other is measured by their standard cell potentials, presented in Section 17.2. In Section 17.3, the Nernst equation is introduced to allow calculation of potentials of cells that are not in their standard states. 

Learning a few electrical variables and their nnits will enable us to do electrochemical calculations, both for voltaic cells and for electrolysis cells. These are presented in Table 17.1. In this section, potential, also called voltage, is the important unit. Potential is the tendency for an electrochemical half-reaction or reaction to proceed. In this section, we will be using the standard half-cell potential, symbolized e°. Standard half-cell potentials can be combined into standard cell potentials, also symbolized e°. The snperscript ° denotes the standard state of the system, which means that the following conditions exist in the cell ... 

Over the years, chemists have measured and recorded the standard reduction potentials, abbreviated of many different half-cells. Table 21-1 lists some common half-cell reactions in order of increasing reduction potential. The values in the table are based on using the half-cell reaction that is being measured as the cathode and the standard hydrogen electrode as the anode. All of the half-reactions in Table 21-1 are written as reductions. However, in any voltaic cell, which always contains two halfreactions, the half-reaction with the lower reduction potential will proceed in the opposite direction and will be an oxidation reaction. In other words, the half-reaction that is more positive will proceed as a reduction and the half-reaction that is more negative will proceed as an oxidation. 

The final step is to combine the Cu and Zn half-cells as a voltaic cell, which means calculating the voltaic cell s standard potential using the following formula... 

You are given the half-cell descriptions for a voltaic cell and standard reduction potentials in Table 21-1. In any voltaic cell, the half-reaction with the lower reduction potential will proceed as an oxidation. With this information, you can write the overall cell reaction and calculate the standard cell potential. 

The standard potential for this voltaic cell seems reasonable given the reduction potentials of the half-cells that comprise It. The mathematical operations with negative numbers are correct and the answer is correct to the thousandths place. 

The standard potential of a voltaic cell is the difference between the standard reduction potentials of the half-cell reactions. 

On the basis of the standard redaction potentials shown above, which of the following standard cell notations below correctly represents its voltaic cell ... 

---