What is Isopoly and heteropoly?
In other words, isopoly acids contain only one metal along with hydrogen and oxygen while heteropoly acids contain two elements other than hydrogen and oxygen. The corresponding salts of isopoly and heteropoly acids are called as isopoly and heteropoly salts, respectively.
What is heteropoly anion?
Heteropoly anions can be regarded as coordination compounds with polyanion ligands; e.g., [(H3N)5Cr(OH2)]3+ can be considered the parent of [(SiW11O39)Cr(OH2)]5−. A variety of synthetic procedures are available for the preparation of isopoly acids and salts, which are usually less stable than heteropoly compounds.
What are Isopoly acids?
Definition of isopoly acid : any of a large group of complex oxygen-containing acids derived from a single inorganic acid by elimination of water from two or more molecules —distinguished from heteropoly acid.
What is heteropoly salt?
…heteropoly acids, which can form heteropoly salts. The condensation reactions, which occur reversibly in dilute aqueous solution, involve formation of oxo bridges by elimination of water from two molecules of the weak acid.
What are Polyacids write in detail?
having more than one replaceable hydrogen atom. capable of reacting with more than one equivalent weight of an acid.
What is a Keggin ion?
Keggin structure is the best known structural form for heteropoly acids. It is the structural form of α-Keggin anions, which have a general formula of [XM12O40]n−, where X is the heteroatom (most commonly are P5+, Si4+, or B3+), M is the addendum atom (most common are molybdenum and tungsten), and O represents oxygen.
How do you make molybdenum blue?
Dispersions of molybdenum blue were synthesized by reducing a solution of ammonium heptamolybdate with ascorbic acid acidified with hydrochloric acid.
What is molybdenum trioxide used for?
Molybdenum Trioxide is a white, odorless powder which turns yellow when heated. It is used in agriculture, making other Molybdenum compounds, ceramic glazes, enamels, pigments, and analytical chemistry.
How are Isopoly acids classified?
Isopolyacids : where the acids/anions which condense together are all of the same type. ie, all Mo O6 groups or all WO6 groups. Hetropolyacids : where two or more different types of anions condense together ie, molybdate or tungstate groups with phosphate (PO4)3- , silicate (Si O4)4- or borate groups.
What is a Polyacidic base?
Taking the example of a few bases such as calcium hydroxide, aluminium hydroxide, we can see that they contain more than one ionizable ion per molecule of base. Such acids are termed as poly-acidic bases.
What is meant by heteropoly compounds?
Heteropoly compounds in the solid state are ionic crystals (sometimes amorphous) consisting of large polyanions, cations, water of crystallization,and other molecules. This three-dimensional arrangement is called the “secondary structure.”
What is the reduction potential of heteroatoms with catalysis?
As for heteroatoms, the reduction potential (or oxidizing ability) decreases linearly with a CATALYTIC CHEMISTRY OF HETEROPOLY COMPOUNDS 193 x Y Gi . ‘ 0 -3 -4 -5 -6 -7 Anion charge FIG. 49. Dependence of reduction potentials on anion charge: ( 0 ) XMWllO&; (0) XMMolIO [;R;SCE = saturated calomel electrode.
What are the characteristics of heterogeneous acid catalyzed reactions?
Heterogeneous Acid-Catalyzed Reactions A. GENERAL CHARACTERISTICS Among heteropolyacids, polytungstic acids are the most widely used catalysts owing to their high acid strengths, thermal stabilities, and low reducibilities.
How do photoexcited heteropolyanions react with organic species?
The photoexcited heteropolyanions react with organic species, accompanied by formation of H’ and/or electron transfer, resulting in the reduction of heteropolyanions and the oxidation of organic reactants [Eq. (52)]. The reduced heteropolyanions are reoxidized by dioxygen according to Eqs. (56) and (57).