Mixtures of Acids

Finding the pH of a mixture of acids may seem difficult at first. However, in many cases, the relative strengths of the acids in the mixture allow us to neglect the weaker acid and focus only on the stronger one. Here, we consider two possible acid mixtures a strong acid with a weak acid, and a weak acid with another weak acid. 

A Strong Acid and a Weak Acid Consider a mixture that is 0.10 M in HCl and 0.10 M in HCHO2. There are three sources of H30 ions the strong acid (HCl), the weak acid (HCHO2), and the autoionization of water. 

Since HCl is strong, we know that it completely ionizes to produce a significant concentration of H30 (0.10 M). The H30 formed by HCl then suppresses the formation of additional H30 formed by the ionization of HCHO2 or the autoionization of water. In other words, according to Le Chatelier s principle, the formation of H30 by the strong acid causes the weak acid to ionize even less than it would in the absence of the strong acid. To see this clearly, let us calculate [H30 ] and [CHO2 ] in this solution. 

In an initial estimate of [H30 ], we can neglect the contribution of HCHO2 and H2O. The concentration of H30 is then equal to the initial concentration of HCl. 

To find [CHO2 ] we must solve an equilibrium problem. However, the initial concentration of H30 in this case is not negligible (as it has been in all the other weak acid equilibrium problems that we have worked so far) because HCl has formed a significant amount of H30. The concentration of H3O+ formed by HCl becomes the initial concentration of H30 in the ICE table for HCHO2 as shown here  

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Isovaleric acid, Me2CHCH2COOH, is a colourless liquid with the unpleasant odour of valerian, b.p. 177 "C. Occurs in the roots of valerian and angelica together with an optically active form of methylethylethanoic acid. Prepared by oxidation of isoamyl alcohol. A mixture of acids similar to that obtained from valerian roots is prepared by oxidation of fusel oil. 

Heptaoxodiphosphoric acid, H PjO, as its old name suggests, is formed as one product when phosphoric(V) acid is heated (loss of water on heating leads to a mixture of acids). It forms two series of salts, the sodium salts, for example, have the formulae Na2H2P207 and Na4P207. 

The aqueous solution is safe to handle, the dissolution being essentially physical. On standing in sunlight the solution slowly decomposes to a mixture of acids. In alkaline solution a mixture of chlorate(lll), CIO2, and chlorate(V), CIO J, ions is rapidly produced. Chlorine dioxide is paramagnetic, the molecule containing an odd electron and having a structure very like that of NOj (p. 231). 

Removal of acids from mixtures of acids and neutral compounds. 

Removal of acids from mixtures of acids and neutral substances. Prepare a column of a strong base anion resin and treat it with sodium... 

The approach that we have worked out for the titration of a monoprotic weak acid with a strong base can be extended to reactions involving multiprotic acids or bases and mixtures of acids or bases. As the complexity of the titration increases, however, the necessary calculations become more time-consuming. Not surprisingly, a variety of algebraic and computer spreadsheet approaches have been described to aid in constructing titration curves. 

Earlier we noted that an acid-base titration may be used to analyze a mixture of acids or bases by titrating to more than one equivalence point. The concentration of each analyte is determined by accounting for its contribution to the volume of titrant needed to reach the equivalence points. 

Castillo, C. A. Jaramillo, A. An Alternative Procedure for Titration Curves of a Mixture of Acids of Different Strengths, /. Chem. Educ. 1989, 66, 341. 

The term naphthenic acid, as commonly used in the petroleum industry, refers collectively to all of the carboxyUc acids present in cmde oil. Naphthenic acids [1338-24-5] are classified as monobasic carboxyUc acids of the general formula RCOOH, where R represents the naphthene moiety consisting of cyclopentane and cyclohexane derivatives. Naphthenic acids are composed predorninandy of aLkyl-substituted cycloaUphatic carboxyUc acids, with smaller amounts of acycHc aUphatic (paraffinic or fatty) acids. Aromatic, olefinic, hydroxy, and dibasic acids are considered to be minor components. Commercial naphthenic acids also contain varying amounts of unsaponifiable hydrocarbons, phenoHc compounds, sulfur compounds, and water. The complex mixture of acids is derived from straight-mn distillates of petroleum, mosdy from kerosene and diesel fractions (see Petroleum). 

A significant advance in metal soap technology occurred in the 1920s with the preparation of the metal naphthenates. Naphthenic acids (qv) are not of precise composition, but rather are mixtures of acids isolated from petroleum. Because the mixture varies, so does acid number, or the combining equivalent of the acid, so that the metal content of the drier would not always be the same from lot to lot. The preparation of solvent solutions of these metal naphthenates gave materials that were easy to handle and allowed the metal content to be standardized. Naphthenates soon became the standard for the industry. 

The small tendency of oxaziridines to undergo hydrolytic C—O cleavage is underlined by the observation that oxaziridine (52) in a mixture of acid and 0-labeled water yields up to 50% labeled hydroxylamine. NH transfer to water successfully competes with hydrolysis (B-67MI50800). 

The valve was made of Hastelloy, an alloy suitable for use on the unit where it was found but not suitable for use with the mixture of acids on the unit on which it had been installed. 

Carboxylative TMM q cloaddition has also been realized with 3-methoxytropone and precursor (56) to produce an epimeric mixture of acids (122), which was employed in a synthetic study of the bicyclic diterpene sanadaol (123). The use of bi-dentate ligand tpdp (12) and high pressure did not improve the reaction. However, the addition of MesSnOAc as a co-catalyst did produce a better yield of (122) (Scheme 2.33) [16]. 

A less accurate but more colorful way to measure pH uses a universal indicator, which is a mixture of acid-base indicators that shows changes in color at different pH values (Figure 13.5, p. 359). A similar principle is used with pH paper. Strips of this paper are coated with a mixture of pH-sensitive dyes these strips are widely used to test the pH of biological fluids,... 

Polyprotic acids (or mixtures of acids, with dissociation constants AT, K2, and AT3) and strong bases. The first stoichiometric end point is given approximately... 

The method may be used to titrate a mixture of acids which differ greatly in their strengths, e.g. acetic (ethanoic) and hydrochloric acids the first break in the titration curve occurs when the stronger of the two acids is neutralised, and the second when neutralisation is complete. For this method to be successful, the two acids or bases should differ in strength by at least 10s to 1. 

It is used to prepare symmetrical RR, where R is straight or branched chained, except that little or no yield is obtained when there is a branching. The reaction is not successful for R = aryl. Many functional groups may be present, though many others inhibit the reaction." Unsymmetrical RR have been made by coupling mixtures of acid salts. 

Addition of a Co(III) sulphate solution in sulphuric acid to an olefin dissolved in acetic acid results in reduction of Co(III) at a rate commensurate with that observed for aqueous solution and with identical kinetics " Prior treatment of the Co(III) solution with acetic acid, however, causes the rate of reduction of Co(III) to become almost independent of olefin concentration. Evidently a Co(III)-acetate complex is formed in the mixture of acids which oxidises only after a rate-determining dissociation. However, this complex cannot be formed instantly, and uncomplexed Co(III) can attack olefins in acetic acid in a manner similar to that in water. 

Electropolishing is performed in concentrated mixtures of acids (sulfuric, phosphoric, chromic, etc.). Often, organic acids and glycerol are added. It is somewhat inconvenient that almost all metals and alloys require their own solution composition. For electropolishing, intermediate and high current densities are used, between about 0.1 and 500 mA/cm. Depending on current density, the process requires between 30 s and 20 to 30 min. Usually, a metal layer 2 to 5 pm thick is removed under these conditions. 

Inorganic solvents (acids, bases, salt solutions, mixtures of acids bases, and their salts). 

The peculiarity of this material is that it consists of a mixture of acids and not triglycerides therefore, its transformation in biodiesel requires only an esterification reaction instead of a irans -esterification one and therefore does not produce glycerol, making the total economy lighter and independent of the critical... 

Various additive mixtures have been proposed for inclusion in blood collection tubes to prevent in vitro platelet activation. One formulation involves the use of a mixture of acid-citrate-dextrose (ACD, 1 5 dilution), 30 p-M acetylsalicylic acid... 

Fig. 3.3f(/) shows the use of a combination of ion-pairing and ion-suppression to separate a mixture of acids and bases. The pH of the mobile phase is about 2.5, as at this pH the maleic acid is unionised and elutes quickly as a very polar molecule on the reverse phase column. The other solutes are all weak bases which at pH 2.5 are fully protonated and pair with the pentane sulphonic acid anion. 

Separation of a mixture of acids and bases by ion-pairinglion-suppression... 

Brain Wet ashing of sample with mixture of acids, mixing with Metex and analysis ASV No data No data Jason and Kellogg 1981... 

Here, when you add an acid, the amino group, the strongest base, gets the proton first. If you add a base to a mixture of acids, the strongest acid gives up protons first. 

Pcnniman A process for oxidizing petroleum, or its distillates, to mixtures of acids, phenols, and aldehydes. Powdered coal or coke is added to the petroleum, and air is passed through under high temperature and pressure. Invented by W. B. D. Penniman in 1925. 

Catalytic fading of certain mixtures of acid dyes on nylon, wool and their blends is a particularly significant problem of dye selection for carpets [165]. Xenotest ratings as low as 3-4 (much bluer) were found for green shades on nylon containing an azopyrazolone component such as Cl Acid Yellow 19 (3.150), which fades much more rapidly in the presence... 

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