Galvanic cell Voltaic cells

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). 

Anion a negatively charged ion it migrates to the anode of a galvanic or voltaic cell. 

Anode the electrode in a galvanic or voltaic cell at which electrochemical oxidation takes place. 

Figure 2. Comparison of galvanic and voltaic cells with metal/solution interfaces.

A battery (or galvanic or voltaic cell) is a device that uses oxidation and reduction reactions to produce an electric current. In an electrolytic cell, an external source of electric current is used to drive a chemical reaction. This process is called electrolysis. When the electric potential applied to an electrochemical cell is just sufficient to balance the potential produced by reactions in the cell, we have an electrochemical cell at equilibrium. This state also occurs if there is no connections between the terminals of the cell (open-circuit condition). Our discussion in this chapter will be limited to electrochemical cells at equilibrium. 

Galvanic cell. A cell in which a chemical reaction can produce an electric current a voltaic cell. 

An electrochemical cell can be defined as two conductors or electrodes, usually metallic, immersed in the same electrolyte solution, or in two different electrolyte solutions which are in electrical contact. Electrochemical cells are classed into two groups. A galvanic (sometimes, voltaic) cell is one in which electrochemical reactions occur spontaneously when the two electrodes are connected by a conductor. These cells are often employed to convert chemical energy into electrical energy. Many types are of commercial Importance, such as the lead-acid battery, flashlight batteries, and various fuel cells. An electrolytic cell is one in which chemical reactions are... 

It is possible to design a redox reaction such that the oxidation occurs at one location and the reduction occurs at another location. The device is called a galvanic or voltaic cell. The cathode (usually a metal bar or carbon rod) is the electrode where reduction takes place the anode (usually a metal bar or carbon rod) is the electrode where oxidation takes place. The salt bridge allows ions to slowly migrate from one beaker to the other to maintain electrical neutrality in each half-cell. The voltmeter measures the voltage (or potential), V, between the two electrodes. If the temperature is 298 K, and the solutions are 1 M, then the beakers with the electrodes are each considered to be a standard half-cell. 

Now this is a useful reaction if you want to plate out copper onto zinc. However, not many of us have a burning desire to do this But if you were able to separate those two half-reactions so that when the zinc is oxidized, the electrons it releases are forced to travel through a wire to get to the Cu you d have something useful. You d have a galvanic or voltaic cell, a redox... 

Electrochemical cells are fundamentally classified into galvanic (or voltaic) cells and electrolytic cells [5]. 

Noteworthy, the lUPAC definition of an anode and cathode is herein quoted because erroneous definitions in hterature on SC schemes are fi equendy encountered. An anode is the electrode where redox species are oxidized, i.e., the complete removal of one or more electrons from a molecular entity or an increase in the oxidation number of any atom within any substrate or gain of oxygen and/or loss of hydrogen of an organic substrate takes place [3]. The cathode, respectively, is the electrode where redox species are reduced. These definitions apply to electrodes of both an electrochemical cell and a galvanic or voltaic cell. 

Recent progress and main problems of the study of electrochemical equilibrium properties are reviewed for interfaces between two immiscible liquid electrolyte solutions. The discussed properties are mainly described in terms of the Galvani, Volta, zero charge, and surface (dipolar) potentials at the liquid-liquid interfaces and free liquid surfaces. Different galvanic and voltaic cells with liquid-liquid, mainly water-nitrobenzene interfaces, are described. These interfaces may be polarizable or reversible with respect to one or several ions simultaneously. 

GOAL 1 Distinguish among electrolytic cells, voltaic cells, and galvanic cells. 

There are two types of electrochemical cells. A galvanic or voltaic cell produces electric current from a spontaneous reaction, whereas an electrolytic cell has an external current source, such as a battery, to drive a nonspontaneous reaction. Reactions in electrochemical cells are redox reactions since they involve a transfer of electrons from a reducing agent to an oxidizing agent. The reduction reaction withdraws electrons from one electrode, the positive electrode or cathode. The oxidation reaction supplies electrons to the other electrode, the negative electrode or anode. Current flows via an external circuit from the anode to the cathode. 

In principle at least, any spontaneous redox reaction can serve as a source of energy in a voltaic (galvanic) cell. The cell must be designed in such a way that oxidation occurs at one electrode (anode) with reduction at the other electrode (cathode). The electrons produced at the anode must be transferred to the cathode, where they are consumed. To do this, the electrons move through an external circuit, where they do electrical work. 

Until now, the emphasis has been on voltaic (galvanic) cells, electrochemical cells in which chemical change is used to produce electricity. Another type of electrochemical cell—the electrolytic cell—uses electricity to produce a nm-spontaneous reaction. The process in which a nonspontaneous reaction is driven by the application of electric energy is called electrolysis. 

Comparison of the voltaic/galvanic cell with the electrolytic cell. 

Italian physicist Alessandro Volta demonstrates the galvanic cell, also known as the 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 ... 

---