Neutralization titrations applications

Spreadsheet Summary In Chapter 8 of Applications of Microsoft Excel in Analytical Cheniistiy, we extend the treatment of neutralization titration curves to polyfunctional acids. Both a stoichiometric approach and a master equation approach are used for the titration of maleic acid with sodium hydroxide. 

Neutralization titrations are used to determine the innumerable inorganic, organic, and biological species that possess inherent acidic or basic properties. Equally important, however, are the many applications that involve conversion of an analyte to an acid or base by suitable chemical treatment followed by titration with a standard strong base or acid. 

PART III Classical Methods of Analysis 311 Chapter 12 Gravimetric Methods of Analysis 314 Chapter 13 Titrimetric Methods Precipitation Titrimetry 337 Chapter 14 Principles of Neutralization Titrations 368 Chapter 15 Titration Curves for Complex Acid/Base Systems 395 Chapter 16 Applications of Neutralization Titrations 428 Chapter 17 Complexation Reactions and Titrations 449... 

The last definition has widespread use in the volumetric analysis of solutions. If a fixed amount of reagent is present in a solution, it can be diluted to any desired normality by application of the general dilution formula V,N, = V N. Here, subscripts 1 and 2 refer to the initial solution and the final (diluted) solution, respectively V denotes the solution volume (in milliliters) and N the solution normality. The product VjN, expresses the amount of the reagent in gram-milliequivalents present in a volume V, ml of a solution of normality N,. Numerically, it represents the volume of a one normal (IN) solution chemically equivalent to the original solution of volume V, and of normality N,. The same equation V N, = V N is also applicable in a different context, in problems involving acid-base neutralization, oxidation-reduction, precipitation, or other types of titration reactions. The justification for this formula relies on the fact that substances always react in titrations, in chemically equivalent amounts. 

Another interesting application area of PHMD simulations is to investigate electrostatic interactions in the unfolded states of proteins. A traditional view that unfolded proteins adopt random conformational states that are devoid of electrostatic and hydrophobic interactions, are recently challenged by experimental data [20, 69], REX-CPHMD folding simulations of the 35 residue C-terminal subdomain of the villin headpiece domain revealed a significant deviation from the standard pKa values for several titratable residues. Additional simulations, in which a charged group is neutralized confirmed the existence of specific electrostatic interactions in the unfolded states (JK and CLB, manuscript in preparation). 

One important application of acid-base titrations is the determination of the alkalinity of various kinds of samples. It is an especially important measurement for the proper treatment of municipal water and wastewater. Alkalinity of a water sample is defined as its acid-neutralizing capacity. It is determined by titrating the water sample with standard acid until a particular pH is achieved. The alkalinity value... 

This method is especially suited to the trithionates and tetrathionates, and is applicable even in the presence of thiosulphate or sulphite by first titrating the neutral solution with iodine, which indicates the total quantity of sulphite and thiosulphate, and then determining the acidity developed during the iodine titration, from which the amount of sulphite can be calculated. Finally the mercuric chloride reaction is applied to another portion of the original solution and by determination... 

In the application laboratory, students determine the quantity of carbon dioxide produced from the decay of leaves over a given period of time and report their results as milligrams of C02 per gram of leaf per day. They set up compost jars and a control jar a week in advance to give the leaves a chance to decay. The students back titrate to determine the number of moles of sodium hydroxide left unreacted, which enables them to ultimately determine the quantity of carbon dioxide produced from the decay of the leaves. The previously done skill -building laboratory has given them experience with back titrations when they analyzed the number of moles of hydrochloric acid neutralized by different commercial antacids. 

Reinvestigation of the excited state acid-base properties of 2-naphthylamine (Schulman and Capomacchia, 1972) showed that a reported change of hybridization from sp3 to sp2 on excitation had little effect on the entropy of protonation of nitrogen in the Sx state and that therefore the Forster cycle was still applicable. A pX (S1 )-value, calculated from the fluorescence maxima of the B and BH+ form, of —8-1 is in poor agreement with the value, —2, obtained from fluorescence titration measurements. From the acidity dependence of fluorescence intensity for 1- and 2-naphthylamine Liedke and Schulman (1973a) found that the decrease in emission of the B form occurred at lower acidities than the appearance of BH+ fluorescence. [A similar titration curve for the fluorescence of the neutral molecule was obtained by Seliskar and Brand (1971), who obtained a value of 0-64 for pkr(S1) from the decrease of the... 

To study nonexchangeable acidity, active and exchangeable acidity has to be blocked (Hargrove and Thomas 1982 Thomas and Hargrove 1984). In potentio-metric titration, the main source of exchangeable acidity is the permanent charge of aluminosilicates, which can be neutralized by a support electrolyte in high concentration (e.g., 0.1 mol/dm3 sodium salt) (Chapter 2, Section 2.4.3). The application of the support electrolyte makes it possible to use the constant capacitance model, too. 

Electrometric Titration Precipitation Reactions.—One of the most important practical applications of electrode potentials is to the determination of the end-points of various typos of titration the subject will be treated here from the standpoint of precipitation reactions, while neutralization and oxidation-reduction processes are described more conveniently in later chapters. 

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