Electrochemistry is a branch of chemistry that studies the transformation between electrical energy and chemical energy. In other words, the chemical reactions that occur at the interface of an electrical conductor (called an electrode, which can be a metal or a semiconductor) and an ionic conductor (the electrolyte), which can be a solution and in some special cases, a solid. .
Summary
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- 1 Concept of electrochemistry
- 2 Redox reactions
- 1 Adjustment of Redox equations
- 3 Electrochemical Cell
- 4 Electrochemical corrosion
- 5 Applications
- 6 Source
- 7 external links
electrochemistry concept
Electrochemistry branch of chemistry that deals with the relationship between electrical currents and chemical reactions, and the conversion of chemical energy into electrical energy and vice versa. In a broader sense, electrochemistry is the study of chemical reactions that produce electrical effects and of chemical phenomena caused by the action of currents or voltages.
It is for this reason that the field of electrochemistry has been divided into two large sections. The first one is Electrolysis, which refers to the chemical reactions that are produced by the action of an electric current. The other section refers to those chemical reactions that generate an electric current, this process is carried out in a galvanic cell or battery.
If a chemical reaction is driven by an externally applied potential difference, it is referred to as electrolysis. On the other hand, if the electrical potential drop is created as a consequence of the chemical reaction, it is known as an “electrical energy accumulator”, also called a battery or galvanic cell.
redox reactions
The chemical reactions where a transfer of electrons between molecules occurs are known as redox reactions, and their importance in electrochemistry is vital, because through this type of reaction the processes that generate electricity are carried out or otherwise, they are produced as consequence of it.
In general, electrochemistry is responsible for studying the situations where oxidation and reduction reactions occur, being separated, physically or temporarily, in an environment connected to an electrical circuit. The latter is the subject of study in analytical chemistry, in a subdiscipline known as potentiometric analysis.
In these reactions, the energy released from a spontaneous reaction is converted into electricity or can be used to induce a non-spontaneous chemical reaction.
Fitting of Redox Equations
Electrochemical reactions can be adjusted by the ion-electron method where the global reaction is divided into two half-reactions (one of oxidation and the other of reduction), the charge and element adjustment is made, adding H+, OH−, H2O and/or electrons to compensate for oxidation changes. Before starting to balance, it is necessary to determine in which medium the reaction occurs, because it proceeds in a particular way for each medium.
Electrochemical cell
It is the device used for the decomposition by electric current of ionized substances called electrolytes. It is also known as a galvanic or voltaic cell, in honor of the scientists Luigi Galvani and Alessandro Volta, who manufactured the first of this type at the end of the 18th century.
Electrochemistry
Scheme of the Daniell cell. The salt bridge (represented by the inverted U-shaped tube) contains a KCl solution allowing electrical interaction between the anode and cathode. The ends of this must be covered with pieces of cotton to prevent the KCl solution from contaminating the other containers.
Electrochemical cells have two electrodes: the anode and the cathode. The anode is defined as the electrode where the oxidation takes place and the cathode where the reduction takes place. The electrodes can be made of any material that is an electrical conductor, such as metals, semiconductors. Graphite is also widely used due to its conductivity and low cost. To complete the electrical circuit, the solutions are connected by a conductor through which the cations and anions pass, known as a salt bridge (or as a salt bridge).
The dissolved cations move towards the cathode and the anions towards the anode. Electric current flows from the anode to the cathode because there is a difference in electric potential between the two electrolytes. That difference is measured with the help of a voltmeter and is known as the cell voltage. It is also called electromotive force (emf) or as cell potential.1 In a galvanic cell where the anode is a Zinc bar and the cathode is a Copper bar, both submerged in solutions of their respective sulfates, and joined by a salt bridge is known as Daniell’s Pile. Its semi-reactions are these:
- Anodic reaction Zn(s)= Zn 2+(aq) + 2 e –
- Cathodic Reaction Cu 2+(aq) + 2e – = Cu(s)
- Total reaction Zn (s) + Cu 2+(aq) = Zn 2+ (aq)+ Cu (s)
The conventional notation for representing electrochemical cells is a cell diagram. Under normal conditions, for the Daniell cell the diagram would be:
Zn(s)/Zn 2+ (aq)//Cu 2+ (aq)/Cu(s)
This diagram is defined by: anode –> cathode Negative electrode/electrolyte // Electrolyte/positive electrode (the / indicates flow of electrons and the // means salt bridge)
The vertical line represents the boundary between two phases. The double vertical line represents the salt bridge. By convention, the anode is written first on the left and the other components appear in the same order as they are when moving from anode to cathode.
electrochemical corrosion
Electrochemical corrosion is a spontaneous process that always denotes the existence of an anodic zone (the one that suffers corrosion), a cathodic zone and an electrolyte, and the existence of these three elements is essential, in addition to a good electrical union between anodes and cathodes, so that this type of corrosion can take place. The most frequent corrosion is always of an electrochemical nature and results from the formation on the metallic surface of a multitude of anodic and cathodic zones; the electrolyte is, in case the metal is not submerged or buried, the condensed water of the atmosphere, for which the relative humidity must be 70%.
The process of dissolving a metal in an acid is also an electrochemical process. The infinity of bubbles that appear on the metallic surface reveals the existence of infinite cathodes, while in the anodes the metal dissolves. With the naked eye it is impossible to distinguish between an anodic and a cathodic zone, given their microscopic nature (galvanic micropiles). As the anodic and cathodic zones continuously change position, there comes a time when the metal dissolves completely.
Applications
Electrolytic decomposition is the basis for a large number of very important extraction and manufacturing processes in modern industry. Caustic soda (an important chemical in the manufacture of paper, rayon, and photographic film) is produced by the electrolysis of a solution of common salt in water. The reaction produces chlorine and sodium .
The sodium in turn reacts with the water in the electrolytic cell to produce caustic soda. The chlorine obtained is used in the manufacture of wood pulp and paper.
An important industrial application of electrolysis is the electric furnace, which is used to make aluminum, magnesium, and sodium. In this furnace, a charge of metallic salts is heated until it melts and ionizes. The metal is then electrolytically deposited.
Electrolytic methods are also used to refine lead, tin, copper, gold, and silver. The advantage of extracting or refining metals by electrolytic processes is that the deposited metal is of high purity. Electroplating, another electrolytic industrial application, is used to deposit precious metal films on base metals.
It is also used to deposit metals and alloys on metal parts that require a strong and durable coating. Electrochemistry has recently advanced by developing new techniques for layering material on electrodes, thus increasing their efficiency and strength. Following the discovery of certain polymers that conduct electricity, it is possible to make polymer electrodes.
