Weak acids salts

Neutral or weak acid-salt solutions usually can be handled in lead plants, with the exception of those few heavy metals that may form lead alloys by substitution. The alums and sulfates generally have little action. 

Scherrer observed [280,281], as have others [161,162,275], that for a large number of ordinary charged species partitioning into octanol in the presence of aqueous solutions containing 0.15 M KC1 or NaCl, weak-acid salts have values of diff(k)g PN ) equal to 4, and that weak-base salts have cliff values equal to 3. These are helpful numbers to keep in mind when predicting the values of log P1 when log PN is known. 

XI. Strong Add + Salt of Weak Acid - Salt of Strong Acid + Weak Acid... 

The establishment of the equilibrium is often accelerated by acidic or basic catalysts, for example, by strong acids (p-toluenesulfonic acid), metal oxides (antimony trioxide), Lewis acids (titanium tetrabutoxide, tin acetates or tin oc-toates), weak acid salts of alkali metals or alkaline earth metals (acetates, benzoates), or by alcoholates. 

Kp values may be found in the literature or they may be calculated from AG° values of the weak acid anion and the weak acid. Salts can be formed between cations and the A1(0H)4 anion, these being called tetrahydrox-oaluminates. Those of the alkali metals are soluble, but most others are insoluble. 

The addition of H+ to this solution favours the back reaction while the addition of base favours the forward reaction. The weak acid/salt pair thus acts to minimize ApH. An analogous situation exists for buffers consisting of a weak base and its salt. The pH of a buffer can be calculated from the concentration of its components by the Henderson-Hasselbalch equation... 

As a representative example to explain this phenomenon, the precipitation ofthe weak acid, pamoic acid, employed as the source ofthe counterion, slowed the release rate of benzphetamine in acidic media from a bead containing the weak acid salt ofthe drug (Higuchi and Hamlin, 1963). 

Salts of Weak Acids Salts of weak acids are bases. Most acids are weak acids. Therefore the conjugate bases of these acids have some appreciable base strength. That means that the vast majority of anions increase the pH of a solution. So, what is the pH of a 0.10 M solution of sodium acetate ... 

Converts concentrated weak acid salt solution to pure base solution plus mixed acid/salt stream... 

HON=NOH Hyponitrous acid Weak acid salts are known trails form, Fig. 15.2.3 (a)... 

Consider the titration of a concentration Ca and a volume Va of a weak acid salt KH2A with a concentration Cb and a volume Vb of the strong base NaOH. The electroneutrality equation and the mass balance equation are given by ... 

Acid Weak acid Salt Weak acid... 

Example 19-1 Weak Acid/Salt of Weak Acid Bujfer Solution... 

After some base has been added, but before the equivalence point, a series of weak acid/salt buffer solutions determines the pH. 

Weak acid salt of its conjugate base (represented as HA MA)... 

We will focus first on immediate contributions to acidity and alkalinity. For the acidity of natural waters, the contributors are strong and weak acids, salts of strong acids and weak bases, hydrolysis of Fe and AP, and oxidation and hydrolysis of Fe " and Mn +. 

Preparation.—A historical account of the development of the synthesis of methylenephosphoranes has been given. Details have appeared - of the use of epoxides in the generation of ylides from phosphonium salts. Weakly acidic salts are deprotonated by the anions such as XCHaCH20 formed by attack of the phosphonium covmter-anion on epoxide, but strongly acidic phosphonium salts are deprotonated more rapidly than these species are produced. The base in these cases must be either epoxide or original anion. Side-reactions in olefin syntheses using epoxides as base include acetal formation from aldehyde and epoxide, cyclopropane formation from ylide and epoxide, and decomposition of quinquecovalent phosphoranes, e.g. (1), formed from phosphonium salt and... 

The analysis can be carried out in an exactly similar fashion to that given in Section 5.6.2 for the buffer made from the weak acid/salt of a weak acid buffer, giving ... 

However, there is no such dramatic change when HCl(aq) is added to a buffer, as shown in the following analysis. Consider, for example, the weak acid/weak acid salt with a strong base buffer, i.e. HA/NaA. 

I.2.3. Monoatomic strong base-weak acid type reagents For a monoatomic strong base-weak acid salt... 

Tetrahydropyranylation. This weakly acidic salt is superior to p-TsOH as the calaly.st for teirahydropyranylation of alcohols, particularly acid-.sensitive alcohols... 

A drop of acetic acid added to the condensation reaction mixture helps in improving the 3deld of 3-carbethoxy-coumarin. This is due to the formation of the corresponding saltpiperidinium acetate which being a weakly acidic salt substantially improves the esterification and hence to improve the yield of 3-cabethoxycoumarin. 

The following calculations were then done using ternary weak acid - salt water solubility data in which the solution is saturated with the weak electrolyte to get the activity coefficient of the undissociated portion of the weak acid ... 

Many chemists refer to the salt produced by the reaction of a weak base and a strong acid as a weakly acidic salt. 

In titration curves for weak acids and weak bases, pH changes near the equivalence point are too gradual for color indicators to be used. The solution is buffered both before and after the equivalence point. Figure 19-6 shows the titration curve for 100.0 mL of 0.100 M CH3COOH solution titrated with 0.100 M aqueous NH3. The pH at the equivalence point might not be 7.0, depending on which weak base/weak acid salt is formed. 

---