Chemical Properties of Magnesium Oxide

Structural Properties (Data Obtained from General References) 

The physical and chemical properties of magnesium oxide are primarily governed by the source of the precursor, that is, derived from magnesite or precipitated from brine or seawater. Other important factors include time and temperature of calcination and the presence of trace impurities. Electron microscope studies have revealed that the precursor particle morphology has a large impact on the morphology of the final MgO particle. It has been shown that when brucite and magnesite crystals are thermally decomposed at low temperatures, pseudomorphs of a size and shape similar to the parent crystal are formed. 

Caustic-calcine magnesias are calcined below 900°C and are characterized by moderate to high chemical reactivities. They are readily soluble in dilute acids and hydrate rapidly in cold water. They also slowly react with atmospheric moisture and carbon dioxide to form the basic carbonate, 5MgO 4C02 xH20. Common test methods for determining the reactivity 

Magnesium oxide has very limited solubility in water. However, an accurate determination is complicated by trace quantities of dissolved carbon dioxide in the water and the purity of the sample, where the presence of lime can introduce error. Another complicating factor is the source of the periclase and what heat treatment it had received. All these factors influence the rate at which equilibrium is reached in solution and hence solubility. Many solubility measurements have been made that have produced a wide variation in results. The most accurate determination to date has produced a result of 8.6 mg/L at 30°C. Caustic-calcined magnesia readily hydrates to the hydroxide on exposure to moisture. 

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Table 3.6 Physical and Chemical Properties of Magnesium Oxide Whiskers...

Strontium [7440-24-6] Sr, is in Group 2 (IIA) of the Periodic Table, between calcium and barium. These three elements are called alkaline-earth metals because the chemical properties of the oxides fall between the hydroxides of alkaU metals, ie, sodium and potassium, and the oxides of earth metals, ie, magnesium, aluminum, and iron. Strontium was identified in the 1790s (1). The metal was first produced in 1808 in the form of a mercury amalgam. A few grams of the metal was produced in 1860—1861 by electrolysis of strontium chloride [10476-85-4]. 

As for magnesium oxide, it should be mentioned that this drops out of the dependence for alkaline-earth oxides, because the chemical properties of magnesium are closer to those of aluminium than to the properties of other members of alkali-metal subgroup (it is the so-called diagonal periodicity). The dependence of oxide solubilities against their melting points exists for the... 

Simple Models. The surface chemical properties of clay minerals may often be interpreted in terms of the surface chemistry of the structural components, that is, sheets of tetrahedral silica, octahedral aluminum oxide (gibbsite) or magnesium hydroxide (brucite). In the discrete site model, the cation exchange framework, held together by lattice or interlayer attraction forces, exposes fixed charges as anionic sites. 

Magnesium is a fairly active metal. It reacts slowly with cold water and more rapidly with hot water. It combines with oxygen at room temperature to form a thin skin of magnesium oxide. It burns with a blinding white light at higher temperatures. Magnesium reacts with most acids and with some alkalis. An alkali is a chemical with properties opposite those of an acid. Sodium hydroxide (common lye) and limewater are examples of alkalis. 

Magnesium Oxide In some cases, metal oxides are converted to a more soluble chemical and dissolve more rapidly. For example, magnesium oxide is relatively insoluble in water, but is converted to a more soluble carbonate form by exposure to body fluids whose buffer is bicarbonate (25). This would be expected to enhance the dissolution of magnesium oxide nanoparticles (25). However, titanium dioxide s most soluble form is the acid chloride. If the particles were porous, the porosity (access to the internal surface area) could enhance solubility stiU further for MgO. Empirical evidence suggests that the aggregated-agglomerated metal oxide nanoparticles have minimal reduction of measured surface area, or solubUity properties that parallel such surface areas. 

Physical and chemical as well catalytical properties of basic oxides depend on the nature of the compound from which the oxide has been prepared. MgO is mostly prepared from soluble magnesium salts, (the nitrate, chloride and acetate are mostly used) by precipitation from aqueous solution and calcination of Mg(0H)2<... 

Production of Sea-water Magnesite Preparation of Natural Magnesite Structure of Magnesium Oxide Physical Properties Chemical Properties... 

GI materials, the second component is a powder produced from an ion-leachable aluminosilicate glass (9), whereas in ZP cements, the powder is essentially pulverized zinc oxide, containing, in some cases, small amounts of magnesium oxide (10). Both powders are chemically basic, and thus react with the aqueous solution of the pol3mieric acid. The acid/base reaction that takes place when powder and liquid components are mixed, transforms the paste to a rigid mass within ten to twenty minutes. The mechanistic details of this reaction, as well as the structure/property relations obeyed by the solid product obtained are not well known at this time. Supposedly, the reaction involves the formation of ionic crosslinks between... 

Apart from the three broad categories of student conceptions discussed above, students displayed several inappropriate conceptions relating to the stractural properties of substances. For example, 14% of students suggested that Mg + ions were present in magnesium ribbon. A second example involved the chemical reaction between copper(II) oxide powder and dilute sulphuric acid. In this instance, 25% of students suggested that Cu + ions were present only in aqueous solution but not in the solid and liquid states. This view was rather unexpected because students had earlier been introdnced to ionic and covalent compounds. It is likely that students had merely rote-learned the general rale without sufficient understanding that ionic solids are formed between metallic and non-metallic elements. 

Although zinc is formally a 4-block element, some of its chemical properties are similar to those of the alkaline earth metals, especially those of magnesium. This is mainly due to zinc s exclusive exhibition of the +2 oxidation state in all its compounds and its appreciable electropositive character. With a standard potential of —0.763 V, zinc is considerably more electropositive than copper and cadmium. 

Comparing the two relative forces of electrostatic attraction that you calculated, you can conclude that ionic bonding is considerably stronger in magnesium oxide. This affects the physical properties and chemical behavior of the two compounds. For example, the melting point of MgO (2,852° C) is much higher than that of LiF (845° C). 

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