Electrolysis electrolytic cell, redox reactions

In an electrolytic cell, electric current drives the chemical reaction. The chemical reaction involved in an electrolytic cell is nonspontaneous. Electric current is used to drive the reaction. This process is called electrolysis and hence the name, electrolytic cell. The reaction involves the transfer of electrons and thus it is a redox reaction. For further understanding of the functioning of an electrolytic cell, we will look at an example of an electrolytic cell involving the electrolysis of molten sodium chloride. Molten sodium chloride is a good conductor of electricity. The melting point of NaCl is around 800° C. 

The quantitative laws of electrochemistry were discovered by Michael Faraday of England. His 1834 paper on electrolysis introduced many of the terms that you have seen throughout this book, including ion, cation, anion, electrode, cathode, anode, and electrolyte. He found that the mass of a substance produced by a redox reaction at an electrode is proportional to the quantity of electrical charge that has passed through the electrochemical cell. For elements with different oxidation numbers, the same quantity of electricity produces fewer moles of the element with higher oxidation number. 

A positive standard cell potential tells you that the cathode is at a higher potential than the anode, and the reaction is therefore spontaneous. What do you do with a cell that has a negative " gii Electrochemical cells that rely on such nonspontaneous reactions cire called electrolytic cells. The redox reactions in electroljdic cells rely on a process called electrolysis. These reactions require that a current be passed through the solution, forcing it to split into components that then fuel the redox reaction. Such cells are created by applying a current source, such as a battery, to electrodes placed in a solution of molten salt, or salt heated until it melts. This splits the ions that make up the salt. 

Except for its source of outside current, the electrolytic cell has the same elements as the electrochemical cell an anode and a cathode placed in an electrolyte in which cations (positive ions) move toward the cathode, and anions (negative ions) move toward the anode. The oxidation half reaction at the anode and the reduction half reaction at the cathode can be added together to find the overall redox reaction for the cell. The process is called electrolysis. If a coating of silver metal is desired on a piece of silver jewelry, electrolysis can be performed to coat or plate the silver jewelry in an electrolytic cell. The electrolyte silver nitrate (AgN03) solution supplies a source of silver ions (Ag+). The cathode is the silver jewelry, from which silver ions are reduced to silver metal. The anode... 

Electrodialysis can be performed with two main cell types multi-membrane cells for dilution-concentration and water dissociation applications, and electrolysis (or electro-electrodialysis [EED]) cells for oxidoreduction reactions. In multimembrane cells, only the membrane transport phenomena intervene, while electrochemical reactions occurring at the electrodes do not interact with the separation process the electrodes are simple electrical terminals immersed in electrolytes allowing the current transfer. The electrolysis cell operates with only one membrane that separates two solutions circulating in each electrode compartment. This application is based on electrode redox reactions, which are electrolysis specific properties. The anode induces oxidations, and reductions occur at the cathode [4]. 

Recall that the voltaic cells convert chemical energy to electrical energy as a result of a spontaneous redox reaction. Electrolytic cells do just the opposite they use electrical energy to drive a nonspontaneous reaction. A common example is the electrolysis of water. In this case, an electric current decomposes water into hydrogen and oxygen. 

Electrical energy can be used to bring about non-spontaneous redox reactions that produce useful products. This process is called electrolysis and takes place in an electrolytic cell. 

An electrolytic cell is a chemical system that uses an electric current to drive a non-spontaneous redox reaction. Electrolysis is the process that takes place in such a cell. 

In contrast to spontaneous redox reactions, which result in the conversion of chemical energy into electrical energy, electrolysis is the process in which electrical energy is used to cause a nonspontaneous chemical reaction to occur. An electrolytic cell is an apparatus for carrying out electrolysis. The same principles underlie electrolysis and the processes that take place in electrochemical cells. Here we will discuss three examples of electrolysis based on those principles. Then we will look at the quantitative aspects of electrolysis. 

In an electrolytic cell, an external energy source makes a nonspontaneous redox reaction (AG > 0) occur. In electrolysis of a molten binary ionic compound (salt), the cation is reduced to the metal and the anion is oxidized to the nonmetal. For an aqueous salt solution, the products depend on whether water or one of the ions of the salt requires less energy to be reduced or oxidized. 

Voltaic cells are based on spontaneous redox reactions. It is also possible for nonspontaneous redox reactions to occur, however, by using electrical energy to drive them. For example, electricity can be used to decompose molten sodium chloride into its component elements Na and CI2. Such processes driven by an outside source of electrical energy are called electrolysis reactions and take place in electrolytic cells. 

ELECTROLYSIS Finally, we focus on nonspontaneous redox reactions, examining electrolytic cells, which use electricity to perform chemical reactions. 

In the electrolytic cell shown in Figure 17.4, electrical energy from the voltage source is used to bring about nonspontaneous redox reactions. The hydrogen and chlorine produced have more potential energy than was present in the hydrochloric acid before electrolysis. 

In a voltaic cell, a spontaneous redox reaction is used to produce electrical current. In electrolysis, electrical current is used to drive an otherwise nonspontaneous redox reaction. An electrochemical cell used for electrolysis is an electrolytic cell. We saw that the reaction of hydrogen wifli oxygen to form water is spontaneous and can be used to produce an electrical current in a fuel cell. By providing electrical current, we can cause the reverse reaction to occur, breaking water into hydrogen and oxygen ( Figure 16.16). 

Electrolysis is the use of electric energy to drive a nonspontaneous redox reaction. An electrochemical cell used for this purpose is called an electrolytic cell... 

In a voltaic cell, a spontaneous redox reaction produces electrical current. In an electrolytic cell, electrical current drives an otherwise nonspontaneous redox reaction through a process called electrolysis. We have seen that the reaction of hydrogen with... 

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