Neutralization titration

For crystal sulfamic acid assay, a simplified procedure of neutralization titration with sodium hydroxide solution may be used. At the end point, Bromothymol Blue (BTB) indicator changes color from yellow to yellowish green. A 1-mL solution of l/2NNaOH is equivalent to 0.0485 g of sulfamic acid. 

Except at the first stage in neutralization titration, i.e. for small values of n, all the molecules in solution are found experimentally to be ionized to the same degree a = n/N. Then... 

In the process of a weak acid or weak base neutralization titration, a mixture of a conjugate acid-base pair exists in the reaction flask in the time period of the experiment leading up to the inflection point. For example, during the titration of acetic acid with sodium hydroxide, a mixture of acetic acid and acetate ion exists in the reaction flask prior to the inflection point. In that portion of the titration curve, the pH of the solution does not change appreciably, even upon the addition of more sodium hydroxide. Thus this solution is a buffer solution, as we defined it at the beginning of this section. 

Figure 3. Dependence of pH on fraction neutralization—titration with NaOH...

In a solvent with weak acidity, the solvent molecule cannot easily release a proton. Thus, the pH region is wider on the basic side than in water some strong bases, whose strengths are leveled in water, are differentiated some very weak acids, which cannot be determined by neutralization titration in water, can be determined. In contrast, in a solvent with strong acidity, a proton is easily released from the solvent molecule. Thus, the pH region is narrow on the basic side strong bases are easily leveled neutralization titrations of very weak acids are impossible. 

Fig. 5.35 Apparatus for controlled-current coulometry. The case for neutralization titration of an acid by internal cathodic generation of OhT. GE generating electrode CE counter electrode.

Endpoint detection in a neutralization titration is ordinarily based on the abrupt change in pH that occurs near the equivalence point. A non-instrumental method of pH measurement much used in simple titrations... 

Neutralization titrations are particularly well-adapted to the conductometric titration because of the very high conductance of the hydronium and hydroxide ions compared with the conductance of the reaction products. In neutralization of strong acids, hydronium ions are being replaced by an equivalent number of less mobile sodium ions, and the conductance decreases as a result of this substitution. At the equivalence point, the concentration of hydronium and hydroxide ions are at a minimum, and the solution exhibits its lowest conductance. After the endpoint, a reversal of slope occurs as the sodium ion and the hydroxide ion concentration from the excess base increase. There is an excellent linearity between conductance and the volume base added, except at very near equivalence point region. Very dilute solutions can be analyzed accurately. 

This chapter provides in troductory material that applies to all types of titrimetric methods of analysis, using precipitation titrimetry to illustrate the various theoretical aspects of the titration process. Chapters 14, 15, and 16 are devoted to the various types of neutralization titrations, in which the analyte and titrants undergo acid/base reactions. Chapter 17 provides information about titrations in which the analytical reactions involve complex formation. These methods are of particular importance for the determination of a variety of cations. Finally, Chapters 18 and 19 are devoted to volumetric methods, in which the analytical reactions involve electron transfer. These methods are often called redox titrations. Some additional titration methods are explored in later chapters. These methods include ampero-metric titration, in Section 23B-4, and spectrophotometric titrations, in Section 26A-4. 

Standard solutions of strong acids and strong bases are used e.xtensively for determining analytes that are themselves acids or bases or that can be converted to such species by chemical treatment. This chapter introduces neutralization titrations, deals with the principles of titration, and discusses the common indicators that are used. In addition, titration curves that are plots of pH versus volume of titrant are explored, and several examples of pH calculations are presented. Titration curves for strong and weak acids and bases are described. 

Like all titrations, neutralization titrations depend on a chemical reaction between the analyte and a standard reagent. The point of chemical equivalence is indicated by a chemical indicator or an instrumental method. The discussion here focuses on the types of standard solutions and the chemical indicators that are used for neutralization titrations. 

The effects of reagent and analyte concentrations on the neutralization titration curves for strong acids are shown by the two. sets of data in Table 14-2. and the... 

Why are the standard reagents used in neutralization titrations generally strong acids and bases rather than weak acids and bases ... 

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