Amphoteric property

Lead dioxide is slightly soluble in concentrated nitric acid and concentrated sulphuric acid, and it dissolves in fused alkalis. It therefore has amphoteric properties, although these are not well characteri.sed since it is relatively inert. 

Acid amides have weakly amphoteric properties, and thus give salts such as CjHsCONHj.HCl with strong acids, and salts of the type C HsCONHNa with strong bases. These compounds have to be prepared at low temperatures to avoid hydrolysis, and are difficult to isolate. The mercury derivatives can, however, usually be readily prepared, because mercuric oxide is too feebly basic to cause hydrolysis of the amide, and the heavy mercuric derivatives crystallise well. 

Acid amides possess weakly amphoteric properties salts such as C,HgCONH3,HCl and C.HgCONHNa... 

In general, the tetracyclines are yellow crystalline compounds that have amphoteric properties (Fig. 2) (15). They are soluble in both aqueous acid and aqueous base. The acid salts tend to be soluble in organic solvents such as 1-butanol, dioxane, and 2-ethoxyethanol In fact, 1-butanol is used to extract the salts from aqueous solution. 

The elements show increasing metallic character down the group (Table 14.6). Carbon has definite nonmetallic properties it forms covalent compounds with nonmetals and ionic compounds with metals. The oxides of carbon and silicon are acidic. Germanium is a typical metalloid in that it exhibits metallic or nonmetallic properties according to the other element present in the compound. Tin and, even more so, lead have definite metallic properties. However, even though tin is classified as a metal, it is not far from the metalloids in the periodic table, and it does have some amphoteric properties. For example, tin reacts with both hot concentrated hydrochloric acid and hot alkali ... 

Tin belongs to the long period elements from Rb to Xe and is a main group element because the 4d shell is filled with electrons. Since the valence electrons are 5s2p2, tin occurs in two valences. Whereas valence 2 is formally always positive, valence 4 has amphoteric properties possessing the formal oxidation states +4 or —4, according to the covalently bound substituents and to the reaction partner. 

In aqueous suspensions, metal oxides have amphoteric properties (4). One can describe the adsorption/desorption of H+ and counterion on surface hydroxyl groups (SOH) using the following mass action equations ... 

This type of interaction is not restricted to one dimension, as indicated in the formulation. The bonds between AsCls and SeOa would be much weaker if the amphoteric properties of the molecules were less well developed. This is analogous to bulk effects in solutions and solvate structures involving amphoteric molecules. 

The principal iron oxides used in catalysis of industrial reactions are magnetite and hematite. Both are semiconductors and can catalyse oxidation/reduction reactions. Owing to their amphoteric properties, they can also be used as acid/base catalysts. The catalysts are used as finely divided powders or as porous solids with a high ratio of surface area to volume. Such catalysts must be durable with a life expectancy of some years. To achieve these requirements, the iron oxide is most frequently dis-... 

The physicochemical characterization of the acidity of the doped alumina performed by microcalorimetry, has been complementarized with the catalytic test of 2-propanol decomposition [175], It was found that the modification of y-Al203 surface properties with small amounts of Ca ", Li+, Nd ", NF+, SO/, Zf +ions changed moderately its amphoteric properties. The catalytic test of 2-propanol... 

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 ... 

Alumina has been widely used in normal phase chromatography. Its surface exhibits amphoteric properties (available as basic, acidic, and neutral alumina) and can react as a cation or an anion exchanger. The surface area is in the usual range around lOOm /g, however, the pore structure is not very favorable as a relatively large portion of narrow pores (<2nm) is present. 

Which of the following unbalanced equation(s) demonstrates aluminum hydroxide s amphoteric properties ... 

CHEMICAL PROPERTIES OF AMINO ACIDS ACID-BASE (AMPHOTERIC) PROPERTIES... 

Tin(II) and Tm(IV) Hydroxides. Prepare tin (I I) and tin(IV) hydroxides in separate test tubes from solutions of tin chlorides. What reagent should be used to precipitate the tin hydroxides Do tin hydroxides exhibit amphoteric properties What tin compounds are known as a- and P-stannic acids How are they prepared Write the equations of the reactions. 

Chromium(VI) oxide is strongly acidic. vanadium(V) oxide is amphoteric, titanium(IV) oxide is inert, and scandium(IH) oxide is basic with some amphoteric properties. 

In general, the tetracyclines are yellow crystalline compounds that have amphoteric properties (Fig. 2). They ate soluble in both aqueous acid and aqueous base. 

The cluster compound [Pt(AuPPh3)8]2+ has been shown to exhibit amphoteric properties, undergoing both electrophilic addition reactions with AgN03 and [Hg2(H20)2](N03)2, as described previously, and nucleophilic addition reactions with small molecules such as CO and CNR... 

Anionic starches are obtained by reaction with phosphoric acid and alkali metal phosphates or by derivatization with carboxymethyl groups.30,31 This modification is primarily used to introduce amphoteric properties into cationic com starch for application on the wet end of the paper machine. Anionic starches with carboxymethyl substitution are used as thickeners in coating colors or as binders in coatings for specialty paper grades. Oxidized starches are inherently anionic but without thickening action. Potato starch already carries sufficient natural anionic charge to provide amphoteric properties after cationization.32... 

Further improvements in the retention of pigment in the paper and enhanced sheet formation are obtained when amphoteric starches are used. Phosphate groups have to be added to cationic cornstarch to produce amphoteric properties. Cationic potato starch has a natural source of anionic charge due to its phosphate content. In recent years, waxy com starches, which consist entirely of amylopectin, have been modified for use as cationic or amphoteric agents for papermaking and surface sizing. 

The copper hydroxide does not dissolve altogether in the excess of the reagent, but the solution acquires a deep blue color which is seen better after the precipitate settles out. This color shows that there must be copper in solution, and that the copper hydroxide possesses amphoteric properties to a slight degree. 

---