Acids amphoteric

The product of the second reaction is sodium aluminate, which contains the alumi-nate ion, Al(OH)4. Other main-group elements that form amphoteric oxides are shown in Fig. 10.7. The acidic, amphoteric, or basic character of the oxides of the d-block metals depends on their oxidation state (Fig. 10.8 also see Chapter 16). 

Acid-base status acidic amphoteric basic... 

Arrhenius acid, Bransted-Lowry acid Arrhenius acid, Bransted-Lowry acid Arrhenius base, Bransted-Lowry base Arrhenius acid, Bransted-Lowry acid amphoteric hydroxide (can act as either an acid or base)... 

The metallic properties increase down any column and towards the left in any row on the periodic table. One important metallic property is that metal oxides are base anhydrides. A base anhydride will produce a base in water. These are not oxidation-reduction reactions. Many metal oxides are too insoluble for them to produce any significant amount of base. However, most metal oxides, even those that are not soluble in water, will behave as bases to acids. A few metal oxides, and their hydroxides, are amphoteric. Amphoteric means they may behave either as a base or as an acid. Amphoterism is important for aluminum, beryllium, and zinc. Complications occur whenever the oxidation number of the metal exceeds +4 as in the oxides that tend to be acidic. 

Figure 3 shows a typical example of the pH-mobility curve for a monobasic drug, donepezil hydrochloride. The observed mobilities at different pHs were well in agreement with the regressed values from Eq. (17). The obtained pKa value is 9.2, which is consistent with the result via the UV method (9.1). Similar results were reported for weak acids, amphoteric compounds, as well as peptides with seven ionic groups (20). 

Some binary hydrides (e.g. those of Groups 16 and 17) behave as acids in aqueous solution, but the majority of acids are oxoacids derived from acidic oxides. This discussion is restricted to the factors influencing the production of acids or bases when oxides dissolve in water. An oxide can be acidic, amphoteric i.e. acidic or basic depending upon conditions) or basic. 

Test the reaction of antimony(III) oxide with water, solutions of hydrochloric and tartaric acids, and also with solutions of alkalies. Write the equations of the reactions. Is antimony(III) oxide acidic, amphoteric, or basic ... 

FIGURE J.3 The location of acidic, amphoteric, and basic oxides in the main groups of the periodic table. Metals form basic oxides, nonmetals form acidic oxides. The diagonal band of amphoteric oxides closely matches the diagonal band of metalloids (recall Fig. B.18). 

In slags consisting mainly of oxides, an acid can be regarded as an acceptor of oxide (O2-) anions, whereas a base is a source of these ions. In the presence of an acid, amphoteric oxides behave as bases, whereas in the presence of a base, they behave as acids. Examples of these are ... 

Behaviour of M02, change from acidic amphoteric weakly basic... 

Acidity and basicity are relative properties. Many compounds are amphoteric and behave as acids or as bases according to a partner. Metal oxides are classified as acidic, amphoteric or basic. Experimentally, this classification corresponds to the adsorption of probe molecules[7, 8]. NH3 is a base probe molecule that reacts with the electron deficient metal atoms (Lewis acid) or the protons adsorbed on the hydrated surface, CO2 is usually considered as acidic and thus it is expected to adsorb more strongly on basic sites. According to this classification, Ti02 belongs to an amphoteric species and MgO to a basic species. A general difficulty for such classifications is that the order can vary with the choice of the probe. The Hard and Soft Bases and Acids theory[9, 10] responds to the necessity to refine the model with a second scale it is better to couple... 

Arrhenius concept Bronsted-Lowry model hydronium ion conjugate base conjugate acid conjugate acid-base pair acid dissociation constant Section 14.2 strong acid weak acid diprotic acid oxyacids organic acids carboxyl group monoprotic acids amphoteric substance autoionization... 

A thermodynamic scale of surface acidity and basicity can be constructed by exploring the acid-base properties of numerous solids and comparing the heats of adsorption and the adsorption uptakes of gas-phase probe molecules (NH3, CO2, SO2). These solids, varying in their physical and chemical properties, have been selected in order to cover a wide range of acid-base behaviours representative of acidic, amphoteric and basic solids. They can be divided into three main groups according to their adsorption properties towards acidic probes (which interact with basic solids) or basic probe molecules (which adsorb on acidic solids). Amphoteric solids display an adsorption edacity towards both acidic and basic probe molecules. 

Rosenblatt, W., Amino acid amphoterics, in Amphoteric Surfactants, 2nd Edn, Lomax E. G. (Ed.), Surfactant Science Series 59, Marcel Dekker, New York (1996), pp. 49-73. 

The pre-purification of barbiturates to be isolated from urine can likewise be carried out by acid ether extraction [43, 56, 166]. Methylene dichloride has been employed also [34]. Acidification with hydrochloric acid is preferable since, if this is performed with weaker, organic acids, amphoteric medicinal components like sulphonamides, are extracted at the same time [166]. After drying the organic phase with sodium sulphate, further purification on a charcoal or alumina column can be carried out [43, 166]. Urine colouring materials can be removed by shaking the ethereal solution with 5% lead acetate solution [56]. After purification, the... 

Only the a-amino-acids, which are the commonest, will be considered. Many are soluble in water, but not in ether, and are almost neutral. They dissolve in alkalis and acids, (amphoteric). They decarboxylate in the soda-lime test, evolving amines. 

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