Acids strength and concentration

Bassam Z. Shakhashiri, "Differences Between Acid Strength and Concentration," Chemical Demonstrations A Handbook for Teachers of Chemistry, Vol. 3 (The University of Wisconsin Press, Madison, 1989) pp. 136-139. The strength of three acids (acetic, hydrochloric, and sulfuric) are compared by reaction with sodium hydroxide. A companion procedure, involving base strength, is also included. 

Chapter 10 Corrosives Inorganic Acids Strength and Concentration pH... 

In the overview to this chapter we noted that the experimentally determined end point should coincide with the titration s equivalence point. For an acid-base titration, the equivalence point is characterized by a pH level that is a function of the acid-base strengths and concentrations of the analyte and titrant. The pH at the end point, however, may or may not correspond to the pH at the equivalence point. To understand the relationship between end points and equivalence points we must know how the pH changes during a titration. In this section we will learn how to construct titration curves for several important types of acid-base titrations. Our... 

Sulfates having alkyl groups from methyl to pentyl have been examined. With methyl as an example, the hydrolysis rate of dimethyl sulfate iacreases with the concentration of the sulfate. Typical rates ia neutral water are first order and are 1.66 x lO " at 25°C and 6.14 x lO " at 35°C (46,47). Rates with alkaH or acid depend on conditions (42,48). Rates for the monomethyl sulfate [512-42-5] are much slower, and are nearly second order ia base. Values of the rate constant ia dilute solution are 6.5 X 10 L/(mol-s) at 100°C and 4.64 X 10 L/(mol-s) at 138°C (44). At 138°C, first-order solvolysis is ca 2% of the total. Hydrolysis of the monoester is markedly promoted by increasing acid strength and it is first order. The rate at 80°C is 3.65 x lO " ... 

Mineral acids are used as catalysts, usually in a concentration of 20— 40 wt % and temperatures of 30—60°C. An efficient surfactant, preferably one that is soluble in the acid-phase upon completion of the reaction, is needed to emulsify the a-pinene and acid. The surfactant can then be recycled with the acid. Phosphoric acid is the acid commonly used in the pine oil process. Its mild corrosion characteristics and its moderate strength make it more manageable, especially because the acid concentration is constandy changing in the process by the consumption of water. Phosphoric acid is also mild enough to prevent any significant dehydration of the alcohols formed in the process. Optimization of a process usually involves considerations of acid type and concentration, temperature, surfactant type and amount, and reaction time. The optimum process usually gives a maximum of alcohols with the minimum amount of hydrocarbons and cineoles. 

If the injected acid itself contains iron (III), a precipitation of the asphaltic products can occur when it comes in contact with certain crude oils. This leads to practically irreversible damage of the zone treated. The amount of precipitate generally increases with the strength and concentration of the acid. Certain organic sulfur compounds, such as ammonium thioglycolate, mercaptoethanol, cysteamine, thioglycerol, cysteine, and thiolactic acid [581], can reduce the iron (HI). 

Effects of acid strength and anion concentration have been studied as well as the effect of monodentate amines.564,565 Phosphines, in particular dppp, have been used as favorable ligands,566,567 but it has been shown that dppp is oxidized by nitrobenzene under the prevailing conditions.568 Giant clusters and heteropolyanions have been used.569,570 The role of nitroso... 

Thus, zeolites may replace such environmentally unfriendly acid catalysts as A1C13 or H2S04 in organic transformations, contributing to cleaner and safer methodologies. The strength and concentration of the acid sites can be modified by controlling the Si/Al ratio, and therefore the zeolite acidity can be adjusted for a particular application. 

The extraction of the lanthanides from nitrate media with TBP [Eq. (11.20)] depends on several factors including pH, nitric acid concentration, ionic strength, and concentration of the elements in the aqueous phase. 

Lead dioxide exhibits amphoteric properties, reacting with both acids and alkalies. With acids, it forms both divalent and tetravalent salts, depending on acid strength and reaction temperature. Thus, it dissolves in concentrated hydrochloric acid at ambient temperature, forming leadfll) chloride with evolution of chlorine ... 

EDTA (ethylenediaminetetraacetic acid) (H02CCH2)2NCH2CH2N-(CH2C02H)2, the most widely used reagent for complexometric titrations. It forms 1 1 complexes with virtually all cations with a charge of 2 or more, effective formation constant Equilibrium constant for formation of a complex under a particular stated set of conditions, such as pH, ionic strength, and concentration of auxiliary complexing species. Also called conditional formation constant. 

Further acid site strength and concentration measurements were reported by Morita et al. (164), who related the acidity measurements to various catalytic reactions. Using Y zeolite (Linde SK-40, 90% H form) activated at 450°C, they observed no acid sites stronger than an H0 of -8.2, although the total acid site concentration was almost twice that of the former investigations (Fig. 21, curve 4). They also measured acid site concentration as a function of decomposition temperature for NH4Y, and found that n-butylamine titration values paralleled results obtained from pyridine adsorption studies (41,151). The maximum total acidity occurred... 

Fowkes et ah (3) brought more physical chemistry into this type of investigation. They measured acid strengths and reaction rates by differential thermal analysis. They found that the chlorinated hydrocarbons —dieldrin and endrin—when mixed with clays, decomposed at a fixed rate independent of concentration. Thus, a zero-order reaction is indicated. 

The initiating systems based on Lewis acids with covalent esters and halides offer some advantages. First, the number of chains can be easily controlled by the concentration of the ester or halide used as an initiator. Second, the polymerization rate and the proportion of carbocationic species may be easily adjusted by the strength and concentration of the Lewis... 

Differentiate between the terms strength and concentration as they apply to acids and bases. When is HC1 strong Weak Concentrated Dilute Answer the same questions for ammonia. 

Wang and coworkers have studied the strength and concentration of acid sites on a MoO /Sn02 catalyst [167]. As shown in Figure 5.29, at least two H signals... 

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