Voltaic cells calculating

Calculating the quantity of work from a given amount of cell reactant Given the emf and overall reaction for a voltaic cell, calculate the maximum work that can be obtained from a given amount of reactant. (EXAMPLE 20.5)... 

The calculated voltage, E°, is always a positive quantity for a reaction taking place in a voltaic cell... 

An interesting application of electrode potentials is to the calculation of the e.m.f. of a voltaic cell. One of the simplest of galvanic cells is the Daniell cell. It consists of a rod of zinc dipping into zinc sulphate solution and a strip of copper in copper sulphate solution the two solutions are generally separated by placing one inside a porous pot and the other in the surrounding vessel. The cell may be represented as ... 

Electrochemical Method.—In this the value of the equilibrium constant K is calculated from the maximum work measured by means of the electromotive force of a voltaic cell (cf. Chap. XVI.). 

The heat of formation of a substance iji a voltaic cell may therefore be calculated from the measured Peltier effects and the electromotive force. 

Using Numbers Calculate the theoretical potential for each voltaic cell and record it in the data table. 

Using Models Calculate the percent error of the voltaic cell potential. 

Why is the percent error calculated in step 4 large for some voltaic cells... 

Review the equation to calculate the potential of a voltaic cell. 

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

In a voltaic cell, a zinc electrode is placed in a solution that is 1.0 M for Zn2+, while a copper electrode is placed in a 1.0 M Cu2+ solution. Calculate the cell potential for the voltaic cell. (Assume a salt bridge is in place.)... 

Sample A voltaic cell is created with two half-cells. In the first half-cell, a copper electrode is placed in a 1.0 M Cu(N03)2 solution. In the second half-cell, a tin electrode is placed in a solution of 1.0 M Sn(N03)2. A salt bridge is placed between the two half-cells to complete the circuit. Assume tin is the anode. Calculate the cell voltage of the voltaic cell. 

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 ... 

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 CHEMLAB at the end of this chapter offers an opportunity to create voltaic cells and calculate cell potentials. 

Calculate the cell potential of voltaic cells that contain... 

It is impossible to measure directly the electrode potentials. Only the electromotive force (emf) of a voltaic cell arising from a combination of two electrodes can be directly measured, which is given as the arithmetical sum or difference of the two electrode potential depending upon their signs. If one of the electrode potential be accurately measured, that of the other may be calculated. The reference electrode arbitrarily chosen for this purpose is the standard hydrogen electrode. Hydrogen gas at 1 atm. pressure and at a temperature of 25°C is slowly bubbled over a platinised platinum electrode which is immersed in a solution of hydrogen ions of unit activity. By convention potential of the half cell reaction... 

There are two inherently different methods by which an electric current interacts with matter (1) An electric current can cause a chemical reaction. (2) A chemical reaction can produce an electric current. The first of these is done in an electrolysis cell, and the second in a voltaic cell, also called a galvanic cell. Two entirely different sorts of calculations are generally used for the two kinds of cells. (Although the same type of calculations done for electrolysis cells can be done for voltaic cells, they are practically never asked for.)... 

A two-electron reaction in a voltaic cell has a standard potential at 25°C of 0.1 30 V. Calculate the value of the equilibrium constant for the reaction. 

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