Acidic solutions defined

The reduction potentials for the actinide elements ate shown in Figure 5 (12—14,17,20). These ate formal potentials, defined as the measured potentials corrected to unit concentration of the substances entering into the reactions they ate based on the hydrogen-ion-hydrogen couple taken as zero volts no corrections ate made for activity coefficients. The measured potentials were estabhshed by cell, equihbrium, and heat of reaction determinations. The potentials for acid solution were generally measured in 1 Af perchloric acid and for alkaline solution in 1 Af sodium hydroxide. Estimated values ate given in parentheses. 

Polytungsta.tes, An important and characteristic feature of the tungstate ion is its abiUty to form condensed complex ions of isopolytungstates in acid solution (38). As the acidity increases, the molecular weight of the isopolyanions increases until tungstic acid precipitates. However, the extensive investigations on these systems have been hampered by lack of weU-defined soHd derivatives. 

The quantity Hq, defined as — log h, is commonly tabulated and corresponds to the pH of very concentrated acidic solutions. 

The EPA defines corrosivity in terms of pH (i.e., wastes with pH <2 or >2.5) or in terms of ability to corrode steel (SAE 20) at a rate of >6.35 mm (0.250 in.) per year at a temperature of 55 C (13°F). This discussion will address corrosivity as it applies to acids and caustics. Acids are compounds that yield H ions (actually HjO ions) when dissolved in water. Common industrial acids include acetic, nitric, hydrochloric, and sulfuric acids. The terms concentrated and dilute refer to the concentrations in solution. Mixing a concentrated acid with enough water will produce a dilute acid. For example, a bottle of concentrated HCl direct from the manufacturer is approximately 12 N in HCl, while a solution of HCl used in a titration may be only 0.5 N. The latter is a dilute acid solution. 

Ho, the acidity function introduced by Hammett, is a measure of the ability of the solvent to transfer a proton to a base of neutral charge. In dilute aqueous solution ho becomes equal to t d Hq is equal to pH, but in strongly acid solutions Hq will differ from both pH and — log ch+. The determination of Ho is accomplished with the aid of Eq. (8-89) and a series of neutral indicator bases (the nitroanilines in Table 8-18) whose pA bh+ values have been measured by the overlap method. Table 8-19 lists Ho values for some aqueous solutions of common mineral acids. Analogous acidity functions have been defined for bases of other structural and charge types, such as // for amides and Hf for bases that ionize with the production of a carbocation ... 

This result helps us to understand the symbol pH, first defined by a Danish chemist, Sorenson. He used the p to stand for the Danish word poienz (power) and H to stand for hydrogen. After a change of sign, pH is the power of ten needed to express the hydrogen ion concentration in moles per liter. In acidic solutions, pH is less than 7 (pH < 7) and in basic solutions, pH is greater than 7 (pH > 7). Table 11-111 expresses the results of Table 11-11 in terms of pH. 

The Hammett equation is not successful for reactions of aliphatic compounds if the normal cr constants are used. A new scale of substituent constants, labeled cr, was invented to allow the extension of the method to such systems. The difference in the rates of hydrolysis of esters in basic versus acidic solutions is used to define the scale. The transition states are... 

A sample of polyester (ca. 1 g, exactly weighed) is dissolved in 20 mL toluene-ethanol mixture (1/1 vol.) and titrated by a solution of KOH in ethanol (0.05 mol/L) using a potentiometric titrator. A blank titration must be performed under the same conditions. Hardly soluble polyesters (e.g., PET) must be dissolved in an o-cresol-chloroform mixture or in hot benzyl alcohol.417 The result (acid content) is normally expressed in mmol COOH/g polyester but may also be given as the acid number, defined as the number of milligrams of KOH required to neutralize 1 g of polyester. [Acid number = (number of mmol COOH/g polyester) x 56.106.]... 

According to this theory, an acid is defined as a proton donor and a base as a proton acceptor (a base must have a pair of electrons available to share with the proton this is usually present as an unshared pair, but sometimes is in a 7t orbital). An acid-base reaction is simply the transfer of a proton from an acid to a base. (Protons do not exist free in solution but must be attached to an electron pair). When the acid gives up a proton, the species remaining still retains the electron pair to which the proton was formerly attached. Thus the new species, in theory at least, can reacquire a proton and is therefore a base. It is referred to as the conjugate base of the acid. All acids have a conjugate base, and all bases have a conjugate acid. All acid-base reactions fit the equation... 

As Figure 17-6 indicates, only a fraction of weak acid molecules undergoes proton transfer to form hydronium ions. Equation defines the percent ionization of any acid solution to be the percentage of the initial concentration... 

Dennison [43] studied the cathodic electrodeposition of CdS from similar acidic solutions at 90 °C. Although the reactions involved could not be defined exactly, two alternative overall processes were considered ... 

An acid is defined as a species that dissociates in aqueous solution to give hydrogen ions and anions, and a base as a species that dissociates in aqueous solution to give hydroxyl ions and cations. 

The radioactivity of the hydrogen sulfide produced by 28 lemons treated with radioactive elemental sulfur dust, 28 lemons treated with radioactive sulfur dioxide gas, and 28 lemons treated with a radioactive sulfuric acid solution is expressed as per cent specific activity (Table II), which for the purpose of this report is defined as ... 

Termination of the plateau at a sufficiently high overpotential. The potential at which a consecutive electrode reaction sets in (e.g., hydrogen evolution in cathodic reactions) is determined by the composition of the electrolyte (specifically, the pH) and by the nature and state of the electrode surface (hydrogen overpotential). The reduction of ferricyanide in alkaline solution on nickel also provides a better-defined plateau in this respect than the deposition of copper in acid solution. 

Tc(III), Tc(IV) and Tc(V) P-diketonate complexes are stable in acid solution. In fact, when a chloroform solution of TcCl2(acac)2 was shaken with 1 M hydrochloric acid solution, no detectable change in the distribution ratio of the complex - defined as the ratio of the concentration of technetium in the organic phase to that in the aqueous phase - was observed over a 24 h period [26]. However, when the technetium complexes were backextracted into aqueous alkaline solution, decomposition occurred [26-29]. In all the cases studied, spectrophotometric investigation revealed that pertechnetate was formed quantitatively as a final product. 

Suppose that we have defined a membership function for the "Low pH" set. Most acid solutions would be, to some degree, members of this fuzzy set. We may want to be able to qualify the description by adding modifiers, such as "very," "slightly," or "extremely" whose use allows us to retain close ties to natural language. The qualifiers that modify the shape of a fuzzy set are known as hedges. We can see the effect of the hedges "very" and "very very" in Figure 8.11. 

An acid is defined as a proton donor within the Lowry-Brpnsted theory (see Chapter 6). Molecules of acid ionize in aqueous solution to form an anion and a proton, both of which are solvated. An acid such as ethanoic acid (VI) is said to be weak if the extent to which it dissociates is incomplete we call it strong if ionization is complete (see Section 6.2). 

The strength (concentration) of a titrant can also be expressed as its titer. The titer of a titrant is defined as the weight (in milligrams) of substance titrated that is consumed by 1 mL of the titrant. Thus it is specific to a particular substance titrated, meaning that it is expressed with respect to a specific substance titrated. For example, if the analyst is using an oxalic acid solution to titrate a solution of calcium oxide, the titer of the oxalic acid solution would be expressed as its CaO titer, or the weight of CaO that is consumed by 1 mL of the oxalic acid solution. Titer is typically used for repetitive routine work in which the same titrant is used repetitively to titrate a given analyte. 

The acetic acid solution is composed of 0.1 M acetate (71) and 0.1 M H+ (H). The sodium hydroxide solution is defined as -0.1 M H. A negative total concentration is of course only a formal notation. The Newton-Raphson routine interprets any negative [H+]tot correctly and computes the free [H+] and [OH-]. 

When platelike crystals of gly with well-developed 010 faces were partially dissolved in solvents containing variable amounts of resolved R a-amino acids, well-defined etch pits were formed only on the (010) face (Figure 30a). These pits exhibited twofold morphological symmetry with surface edges parallel to the a and c axes of the crystal. The enantiotopic (010) face dissolved smoothly (Figure 30b), exactly as it does when the crystal is dissolved in a solution of pure gly. As expected, S amino acids induced etch pits on the (010) face. Racemic... 

An example of the effect of photon irradiation on the flat band potential is shown in Fig. 10-18 this figure compares a Mott-Schott plot with the anodic polarization curve of the dissolution reaction of a semiconductor anode of n-type molybdeniun selenide in an acidic solution in the dark and in the photoexcited conditions. In this example photoe dtation shifts the flat band potential from Em in the dark to pii) in the photoexcited state is about 0.75 V more positive than Em. This photo-shift of the flat band potential, Emi )-Em, corresponds to the change in the potential, of the compact layer due to photoexcitation as defined in Eqn. 10-23 ... 

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