Undergraduate Instrumental Analysis
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Undergraduate Instrumental Analysis
Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15Elec Undergraduate Instrumental Analysisctroanalytical ChemistryElectrochemistry is the area of chemistry that studies the interconversion of chemical energy and electrical energy. Electroanalytical chemistry is the use of electrochemical techniques Io characterize a sample, rhe original analytical applications of electrochemistry, electr Undergraduate Instrumental Analysisogravimetry and polarography. were for the quantitative determination of trace metals in aqueous solutions. The latter method was reliable and sensitiUndergraduate Instrumental Analysis
ve enough to detect concentrations as low as I ppm of many metals. Since that time, many different types of electrochemical techniques have evolved, eSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15Elec Undergraduate Instrumental Analysiselectroactive species. Electroactive species in general may be solvated or complexed, ions or molecules, in aqueous or nonaqueous solvents. Elecưochemical methods are now used not only for trace metal ion analyses, but also for the analysis of organic compounds, for continuous process analysis, and Undergraduate Instrumental Analysisfor studying the chemical reactions within a single living cell. Applications have been developed that are suited for quality control of product streaUndergraduate Instrumental Analysis
ms in industry. in vivo monitoring, materials characterization, and pharmaceutical and biochemical studies, to mention a few of the myriad applicationSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15Elec Undergraduate Instrumental Analysise current, it is possible to extend the sensitivity limits for many electroactive species by three or four orders of magnitude, thus providing a means of analysis at the ppb level.In practice, electrochemistry not only provides a means of elemental and molecular analysis, but also can be used to acq Undergraduate Instrumental Analysisuire information about equilibria, kinetics, and reaction mechanisms from research using polarography. amperometry, conductometric analysis, and potenUndergraduate Instrumental Analysis
tiometry. The analytical calculation is usually based on the determination of current or voltage or on the resistance developed in a cell under conditSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15Elec Undergraduate Instrumental Analysis electrical signals. The equipment is often far less expensive than spectroscopy inslru mentation. Electrochemical techniques are also commonly used as detectors for LC, as discussed in Chapter 13.Coauthor: R.J. Gale. Department of Chemistry. Louisiana State University. Baton Rouge. LA919920unapier Undergraduate Instrumental AnalysisIOSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15.1. FUNDAMENTALS OF ELECTROCHEMISTRYElectrochemistry is the study of reducUndergraduate Instrumental Analysis
tion-oxidation reactions (called redox reactions) in which electrons are transferred from one reactant to another. A chemical species that loses electSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15Elec Undergraduate Instrumental Analysisuses the other species to be reduced; likewise, an oxidizing agent is a species that is itself reduced in a reaction. An oxidation reduction reaction requires that one reactant gain electrons (be reduced) from the reactant which is oxidized. We can write the reduction and the oxidation reactions sep Undergraduate Instrumental Analysisarately, as half-reactions; the sum of the half-reactions equals the net oxidation reduction reaction. Examples of oxidation half reactions include:FeUndergraduate Instrumental Analysis
2+ —> Feu4-c"Cu(s) Cu2+4-2e"AsH,(g) —► As(s) 4-3H+4-3e~II2C2O4 —> 2CO2(g)4-2ir 4-2e"Examples of reduction half-reactions include:Co3++e" —> Co2+(ion-4Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15Elec Undergraduate Instrumental Analysisthat is, if Al'' accepts 3 electrons, it is reduced to Al(s). All of the reduction reactions are oxidation reactions if they are written in the opposite direction. Many of these reactions are reversible in practice, as we shall see.A net oxidation reduction reaction is the sum of the appropriate red Undergraduate Instrumental Analysisuction and oxidation half-reactions. If necessary, the half-reactions must be multiplied by a factor so that no electrons appear in the net reaction.Undergraduate Instrumental Analysis
For example, the reaction between Cu(s), Cu2+, Ag(s), and Ag+ is:Cu(s)4-2Ag+ —> Cu2+4-2Ag(s)We shall see why the reaction proceeds in this direction sSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15Elec Undergraduate Instrumental Analysisach mole of copper gives up 2 moles of electrons, w hile each mole of silver ion accepts only 1 mole of electrons. Therefore the entire reduction reaction must be multiplied by 2, so that there are no electrons in the net reaction after summing the half-reactions:Oxidation reaction: Cu(s) —> Cu2+ 4- Undergraduate Instrumental Analysis 2e“Reduction reaction: 2(Ag’ 4-e —> Ag(s))Net reaction: Cu(s) 4-2Ag' —► Cu2+2Ag(s)The equal numbers of electrons on both sides of the arrow cancel ouUndergraduate Instrumental Analysis
t.Electroanalytical ChemistryVZISimpo PDF Merge and split Unregistered Version - http://www.simpopdf.com Electrochemical redox reactions can be carrieSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15Elec Undergraduate Instrumental Analysis of these parameters provides us with information about the redox reaction, so it is important to understand the relationship between charge, voltage, and current. The absolute value of the charge of one electron is 1.602 X 10 19 coulombs (C); this is the fundamental unit of electric charge. Since 1 Undergraduate Instrumental Analysis.602 X 10 19 c is the charge of one electron, the charge of one mole of electrons is:Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15ElecSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com15ElecGọi ngay
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