Redox chemistry galvanic cells

We are asked to identify the redox chemistry occurring in this battery. The problem provides a description of the chemical composition of a galvanic cell. To determine what redox reactions take place, examine the species present at each electrode. Then use the standard procedure to balance the... 

Electrochemistry is the area of chemistry concerned with the interconversion of chemical and electrical energy. Chemical energy is converted to electrical energy in a galvanic cell, a device in which a spontaneous redox reaction is used to produce an electric current. Electrical energy is converted to chemical energy in an electrolytic cell, a cell in which an electric current drives a nonspontaneous reaction. It s convenient to separate cell reactions into half-reactions because oxidation and reduction occur at separate electrodes. The electrode at which oxidation occurs is called the anode, and the electrode at which reduction occurs is called the cathode. 

There is another way in which electrons can be rearranged in a chemical reaction, and that is through a wire. Electrochemistry is redox chemistry wherein the site for oxidation is separated from the site for reduction. Electrochemical setups basically come in two flavors electrolytic and voltaic (also known as galvanic) cells. Voltaic cells are cells that produce electricity, so a battery would be classed as a voltaic cell. The principles that drive voltaic cells are the same that drive all other chemical reactions, except the electrons are exchanged though a wire rather than direct contact. The reactions are redox reactions (which is why they produce an electron current) the reactions obey the laws of thermodynamics and move toward equilibrium (which is why batteries run down) and the reactions have defined rates (which is why some batteries have to be warmed to room temperature before they produce optimum output). 

Relate chemistry in a redox reaction to separate reactions occurring at electrodes in a galvanic cell. 

In geochemistry, possibly the greatest interest in galvanic cells is in understanding the concept of Eh and its use in determining redox conditions in natural environments ( 12.8.1). In chemistry, it is in determining the activities of solutes. 

The relationship between the equilibrium constant of a redox reaction and the EMF of the corresponding galvanic cell (potential cell) is the subject of Nemst s law. It is of tremendous interest in analytical chemistry from both theoretical and practical points of view. 

Redox Potential and Free Energy. The concept of redox potential, derived from the above experimental setup, has been an invaluable aid in chemistry. The concept is intimately associated with the free energy of an oxidation-reduction reaction, because the reaction in a galvanic cell is reversible and electric energy is made available for useful work. Thus the redox potential becomes a direct measure of the free energy (cf. Chapt. V-2), except that it is expressed in different units. It must always be remembered, however, that the redox potential invariably refers to the reaction with gaseous hydrogen. That is the zero point of the redox scale. 

Electrochemistry is ranked by teachers and students as one of the most difficult curriculum domains taught and learnt in secondary school chemistry (cf. Davies, 1991 Griffiths, 1994). For that reason, in this chapter, we primarily discuss this domain at the secondary level but also make connections to the tertiary level. In many chemistry curricula and textbooks, it is common to divide electrochemistry into two topics redox reactions (oxidation and reduction) and electrochemical cells (galvanic and electrolytic). The usual rationale for this distinction is that students need an understanding of oxidation-reduction to apply it to electrochemical cells. This analytical distinction, based on differences in the location of the half reactions, is used throughout the chapter. 

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