Acid-base equilibria strong bases

Case 1. Salt of a weak acid and a strong base. The equilibrium in a solution of salt MA may be represented by ... 

We can predict the pH at any point in the titration of a polyprotic acid with a strong base by using the reaction stoichiometry to recognize what stage we have reached in the titration. We then identify the principal solute species at that point and the principal proton transfer equilibrium that determines the pH. 

It is also possible to create a redundancy between measurements with models linking several variables. Static and robust models like acid-base equilibrium and gas-liquid equilibrium can be used easily. However, models with strong assumptions and/or with unknown validity should be used with caution. In this last case, we also have to take into account that the model itself can be faulty and a dimension of the state-universe of the corresponding bba is the faulty state of the model. 

Consider a solution of sodium ethanoate, Na+CHjCOO". This is the salt of the weak acid, ethanoic acid, and the strong base, sodium hydroxide. Again, the equilibrium present in water is ... 

In the titration of a weak acid with a strong base, we must consider the acid dissociation equilibrium of a weak acid (Kg) to calculate [H30 ], after the addition of a strong base. Let us consider the titration of 100 mL of a 0.1 M solution of acetic acid (CH3COOH) with 0.1 M NaOH solution. 

Many important synthetic reactions in which C-C bonds are formed involve esters and are brought about by basic reagents. This is possible because the a hydrogens of an ester, such as RCH2C02C2H5, are weakly acidic, and a strong base, such as sodium ethoxide, can produce a significant concentration of the ester anion at equilibrium ... 

We can predict the pH at any point in the titration of a polyprotic acid with a strong base (see Toolbox 11.1). First, we have to consider the reaction stoichiometry to recognize what stage we have reached in the titration. Next we have to identify the principal solute species at that point and the proton transfer equilibrium that determines the pH. We then carry out the calculation appropriate for the solution, referring to the previous worked examples if necessary. In this section, we see how to describe the solution at various stages of the titration our conclusions are summarized in Tables 11.3 and 11.4. 

We come to the same conclusion by looking at the equilibrium constant for the reaction. Because the neutralization reaction of any strong acid with a strong base is the reverse of the dissociation of water, its equilibrium constant, Kn ("n" for neutralization), is just the reciprocal of the ion-product constant for water,... 

In reactions with amine nucleophiles the reaction leads to a zwitterionic adduct that is in rapid acid-base equilibrium with its anionic form, Equation (45). In some cases, the zwitterion is strongly... 

NMR spectroscopy, which was developed in the late 1950s as a most powerful tool for structural analysis of organic compounds, has also proven to be useful for acidity determinations. The measurement of the ionization ratio has been achieved by a variety of methods demonstrating the versatility of this technique. If we consider the general acid-base equilibrium Eq. (1.26) obtained when the indicator B is dissolved in the strong acid HA, then Up, and fcd, respectively, are the rates of protonation and deprotonation. 

This shows that the ionic equilibrium calculation for the salt formed between the weak base and the strong acid is identical for the undissociated acid. Therefore, one may use Equation (2.15), Equation (2.17), and Equation (2.19) for the calculation of H+ in the solution of a salt between a weak base and a strong acid. Equation (2.21a), Equation (2.21b), and Equation (2.21c) may be used for the calculation of OH- in the solution of the salt between a weak acid and a strong base along with Equation (2.20). 

They should be the strong acids, i.e., the acid-base equilibrium should be shifted to the right-hand side ... 

All chemical reactions, at least in theory, are equilibrium reactions. Even the reactions of a strong acid with a strong base to produce water and a salt (Chapter 8), which we considered to proceed until the limiting reactant was used up (Section 10.4), will be shown (Section 19.3) to have a very tiny concentration of or OH (or both) remaiiung at the end of the process. 

Trihydroxybenzoic acid and some substituted salicyclic acids are decarboxylated much faster and their rates can be studied using dilute aqueous solutions of strong acids. In these examples, the first-order rate coefficient, k = rate/Cs, is found to be proportional to the fraction of non-ionized acid, ArCOOH, in the acid—base equilibrium of the substrate [239, 244, 245], viz. 

An important crosscheck is the media restriction. Paths that form reactive cations almost exclusively occur in acidic media. Likewise, paths that form reactive anions are the domain of basic media. No medium can be both a strong acid and a strong base it would neutralize itself. The reactive species in equilibrium-controlled reactions have a limited range of acidities. For example, in neutral water the hydronium ion concentration and the hydroxide ion concentration are both 10 mol/L. Their relative concentrations are defined by = [H ][OH ] = Their p Ta values span 17.4 p fa... 

Apply acid-base equilibrium concepts to salts of strong bases and weak acids... 

Next, we need to consider the curves for [HOAc] and [OAc ] you should refer to Figure 7.3 during the following discussion. In strongly acid solutions, the dissociation of HOAc is suppressed and HOAc is the major form. Since Choac = 1.0 X 10" M, then in acid solutions [HOAc] is essentially constant at 1.0 X 10" M. Conversely, we know that in alkaline solutions [HOAc] becomes very small due to dissociation and that [OAc ] = Choao- For alkaline solutions, then, we can rearrange the acid-base equilibrium expression (substituting Choac for [OAc ]) to... 

Metal ions of +3 oxidation state have a high surface charge density and consequently solvent molecules are tightly held. Resulting from this is the strong tendency for hydrolysis to take place according to an acid—base equilibrium of the type... 

Bott (1985) reported, however, an observation that strongly indicates the presence of the deprotonated form of the alkenediazonium salt 5.30. If this salt is kept with 0.05 equiv. OCDs K" for 20 h in the perdeuterated solvent mixture (CD3)2SO - CD3OD (5 2), almost complete exchange of the a-H for D is observed, but no nitrogen is evolved. It is likely that this exchange represents an acid-base equilibrium (5-7). The conjugate base 5.31 of this reaction is structurally related to the enol 5.25 with (at least) partial cumulative double bonds at the C(a)-atom ... 

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