Stoichiometry acid-base reactions

Quantitative Calculations In acid-base titrimetry the quantitative relationship between the analyte and the titrant is determined by the stoichiometry of the relevant reactions. As outlined in Section 2C, stoichiometric calculations may be simplified by focusing on appropriate conservation principles. In an acid-base reaction the number of protons transferred between the acid and base is conserved thus... 

The discussion of acid-base titrations in Chapter 4 focused on stoichiometry. Here, the emphasis is on the equilibrium principles that apply to the acid-base reactions involved. It is convenient to distinguish between titrations involving—... 

The quantitative aspects of acid-base chemistry obey the principles Introduced earlier in this chapter. The common acid-base reactions that are important in general chemistry take place in aqueous solution, so acid-base stoichiometry uses molarities and volumes extensively. Example Illustrates the essential features of aqueous acid-base stoichiometry. 

In a related application, polyelectrolyte microgels based on crosslinked cationic poly(allyl amine) and anionic polyfmethacrylic acid-co-epoxypropyl methacrylate) were studied by potentiometry, conductometry and turbidimetry [349]. In their neutralized (salt) form, the microgels fully complexed with linear polyelectrolytes (poly(acrylic acid), poly(acrylic acid-co-acrylamide), and polystyrene sulfonate)) as if the gels were themselves linear. However, if an acid/base reaction occurs between the linear polymers and the gels, it appears that only the surfaces of the gels form complexes. Previous work has addressed the fundamental characteristics of these complexes [350, 351] and has shown preferential complexation of cationic polyelectrolytes with crosslinked car-boxymethyl cellulose versus linear CMC [350], The departure from the 1 1 stoichiometry with the non-neutralized microgels may be due to the collapsed nature of these networks which prevents penetration of water soluble polyelectrolyte. 

Two complications can prevent a simple determination or the concentration of each species from a measurement of absorbance at a chosen frequency. Although most of the acid-base reactions of interest result in a one-to-one stoichiometry, one cannot assume this a priori, and two-to-one and three-to-one adducts might also be present. Fortunately, this is usually an easy point to Tesolve. The presence of an isosbeslic point or point of constant absorbance (see Fig. 9.1) is usually a reliable criterion that only two absorbing species (the free acid or base and a single adduct) are present.26... 

We will now deal with the stoichiometry of acid-base reactions in aqueous solutions. The procedure is fundamentally the same as that used previously. 

According to Chapter 11, an acid is a substance that upon dissolving in water increases the concentration of hydronium (H30 ) ions above the value found in pure water, and a base is a substance that increases the concentration of hydroxide (OH ) ions above its value in pure water. Despite the careful language, it is commonplace to view acids and bases as substances that dissociate to give protons (which upon hydration become hydronium ions) and hydroxide ions, respectively. If the dissociation is complete, we can easily calculate the concentration of hydronium and hydroxide ions in the solution and then calculate the yield of acid-base neutralization reactions, and acid-base titrations, by the methods of stoichiometry in solution. But experience shows that many acid-base reactions do not go to completion. So, to predict the amount (or concentration) of... 

Often the enthalpy of reaction is obtained by measuring the equilibrium constant of an acid-base reaction over a range of temperatures. If In K is plotted versus l/T. the slope will be equal to -AH/R. Thus various experimental methods have been devised to measure the equilibrium constant by spectrophotometric methods. Any absorption which differs between one of the reactants (either acid or base) and the acid-base adduct is a potential source of information on the magnitude of the equilibrium constant since it gives the concentration of two of the three species involved in the equilibrium directly and the third indirectly from a knowledge of the stoichiometry of the reaction. For example, consider the extensively studied reaction between organic carbonyl compounds and iodine. The infrared carbonyl absorption is shifted in frequency in the adduct with respect to the free carbonyl compound. Thus the equilibrium mixture exhibits two absorption bands in the carbonyl region of the spectrum (Fig. 9.1) and the relative concentrations of the free carbonyl and the adduct can be obtained.3- Alternatively, one can observe the absorption of the iodine molecule, U, in... 

Teachers report that students get a much better idea of the role of chemistry in society. Contexts are effective in engaging the students. Students are confronted with a lot of knowledge in a short time. They learn a lot. There are still problems however. Using the knowledge gained in other contexts needs to be established more firmly. There is a need for more practice with skills like calculations in stoichiometry, writing equations in precipitation reactions or acid-base reactions. 

The evolution of carbon dioxide essentially follows the stoichiometry of acid—base reactions. Baking soda determines the amount of carbon dioxide evolved, whereas the type of acid controls the speed of liberation. The reaction equations for some acids with baking soda are as follows ... 

Attia reported a potentiometric investigation of the stoichiometry of acid-base reactions of phosphorus acids with oxide ions in molten KN03 at 350 °C... 

An acid-base reaction is often called a neutralization reaction. When just enough strong base is added to react exactly with the strong acid in a solution, we say the acid has been neutralized. One product of this reaction is always water. The steps in dealing with the stoichiometry of any neutralization reaction are the same as those we followed previously. 

Acid-Base Chemistry Acid-base reactions represent another important area of chemistry with applications in engineering, and again we have integrated our coverage into appropriate areas of the text. Initially, we define acids and bases in conjunction with the introduction to solutions in Chapter 3. Simple solution stoichiometry is presented in Chapter 4. Finally, a more detailed treatment of acid-base chemistry is presented in the context of equilibria in Chapter 12. 

Both mono- and dialkylboranes exhibit a simple acid-base reaction in a 1 1 stoichiometry, producing the corresponding alkali metal mono- and dialkylbo-rohydrides (Chart 22.1). 

The principles we learned in Chapter 13 (Section 13.8) on solution stoichiometry can be applied to a common laboratory procedure called a titration. In a titration, a substance in a solution of known concentration is reacted with another substance in a solution of unknown concentration. For example, consider the acid-base reaction between hydrochloric acid and sodium hydroxide ... 

Certain aqueous reactions are useful for determining how much of a particular substance is present in a sample. For example, if we want to know the concentration of lead in a sample of water, or if we need to know the concentration of an acid, knowledge of precipitation reactions, acid-base reactions, and solution stoichiometry will be useful. Two common types of such quantitative analyses are gravimetric analysis and acid-base titration. 

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