Compounds into Elements

Decomposing Compounds into Elements A decomposition reaction occurs when a reactant absorbs enough energy for one or more of its bonds to break. The energy can take many forms we ll focus in this discussion on heat and electricity. The products are either elements or elements and smaller compounds. Following are several common examples  

Notice that the lone reactant is the oxidizing and the reducing agent. 

Electrolytic decomposition. In the process of electrolysis, a compound absorbs electrical energy and decomposes into its elements. Observing the electrolysis of water was crucial in the establishment of atomic masses  

Many active metals, such as sodium, magnesium, and calcium, are produced industrially by electrolysis of their molten halides  

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FIGURE G.5 The hierarchy of materials matter consists of either mixtures or substances substances consist of either compounds or elements. Physical techniques are used to separate mixtures into pure substances. Chemical techniques are used to separate compounds into elements. 

SOURCES of data Values of V d) were chosen to bring the total cohesive energy into agreement wiih experiment for the homopolar solid, and held fixed in the compounds isoelcctronic with them. The theoretical is predicted by using Eq. (7-3) and the values from the first three columns. Experimental values were obtained by adding the heal of formation (the energy required to separate the compound into elements in the standard state), from Wagman ct al. (1968), to the heat of atomization of the elements, from Kittcl (1967, p. 98). A correction of about 0.01 cV/bond should be made to compensate for the different temperatures at which the heat was measured. 

All of the following processes involve a separation of either a mixture into substances or a compound into elements. 

Other volatile compounds of elements can be used to transport samples into the plasma flame. For example, hydride reduction of mercury compounds gives the element (Hg), which is very volatile. Osmium can be oxidized to its volatile tetroxide (OSO4), and some elements can be measured as their volatile acetylacetonate (acac) derivatives, as with Zn(acac)2. 

Laws of Thermochemistry. Lavoisier and Laplace (1780) found that the heat required to decompose a chemical compound into its elements was numerically equal to the heat generated in its formation under the same conditions of T and P. That is, AHj = -AHp where the subscript d refers to decomposition reaction [52, p. 24 61, p. 303]. 

Many different methods can be used to resolve compounds into their elements. Sometimes, but not often, heat alone is sufficient. Mercury(II) oxide, a compound of mercury and oxygen, decomposes to its elements when heated to 600°C. Joseph Priestley, an English... 

Write thermochemical equations for the decomposition of one mole of the following compounds into the elements in their stable states at 25°C and 1 atm. 

The resolution of a chemical compound into its proximate or ultimate parts the determination of its elements or of the foreign substances it may contain thus reads a dictionary definition. 

The small number of elements that make up our world combine to produce matter in a seemingly limitless variety of forms. We have only to look at the vegetation, flesh, landscapes, fabrics, building materials, and other things around us to appreciate the wonderful variety of the material world. A part of chemistry is analysis the discovery of which elements have combined together to form a substance. Another aspect of chemistry is synthesis the process of combining elements to produce compounds or converting one compound into another. If the elements are the alphabet of chemistry, then the compounds are its plays, its poems, and its novels. 

There is little evidence for 1 1 compounds between elements in this group under normal conditions. The diatomic van der Waals molecules, CaMg, SrMg and SrCa, however, have been synthesized by codepositing the atoms from separate sources with argon or krypton into solid matrices at 12 K. These low-T species are identified from their laser-induced fluorescence spectra. The ground-state spectroscopic data for these alkaline-earth dimers form a sensible series between the parent molecules Mg2, Caj and Sr2. ... 

U.S. EPA may list a waste as hazardous for any and all of the above reasons. The majority of listed wastes fall into the toxic waste category. To decide if a waste should be a toxic listed waste, U.S. EPA first determines whether it typically contains harmful chemical constituents. An appendix to RCRA contains a list of chemical compounds or elements that scientific studies have shown to have toxic, carcinogenic, mutagenic, or teratogenic effects on humans or other life forms. If a waste contains chemical constituents found on the appendix list, U.S. EPA then evaluates 11 other factors to determine if the wastestream is likely to pose a threat in the absence of special restrictions on its handling. These additional considerations include a risk assessment and study of past cases of damage caused by the waste. 

Summarizing, it can be said that the accumulation, depletion, or alteration of some compounds or elements in buried bone take place at definable functions of time. Determining the relative amounts of such compounds or elements in bone provides, therefore, information about their age. The information thus obtained should, however, be interpreted with caution and any inherent errors taken into consideration. 

However, each of the individual reactions involves the formation of a compound from its elements or the decomposition of a compound into those elements. The standard enthalpy change of a reaction that involves the formation of a compound from its elements is... 

In addition to the organic chemistry of carbon compounds, the element is also important in inorganic chemistry. In recent years, an extensive chemistry of the fullerenes, C60 and its derivatives, has become one of the most active new areas of inorganic and organic chemistry. There is no clear separation of the two fields even though they were believed to be separate for many years. In 1828, Friedrich Wohler converted ammonium cyanate into urea,... 

In this chapter, we first review the nature of the several forms of elemental phosphorus and then proceed to consider their uses for specific types of syntheses of compounds containing the carbon-phosphorus bond. Prior reviews have also been concerned with these topics.1 2 Our purpose here is to update these presentations and provide fundamentals for the practicing chemist venturing into the use of elemental phosphorus. We limit this discussion to the more-or-less direct syntheses of organophosphorus compounds from elemental phosphorus. We will consider reactions that generate monophosphorus species without C-P bonds as critical intermediates, pro-... 

Certain volatile elements must be analyzed by special analytical procedures as irreproducible losses may occur during sample preparation and atomization. Arsenic, antimony, selenium, and tellurium are determined via the generation of their covalent hydrides by reaction with sodium borohydride. The resulting volatile hydrides are trapped in a liquid nitrogen trap and then passed into an electrically heated silica tube. This tube thermally decomposes these compounds into atoms that can be quantified by AAS. Mercury is determined via the cold-vapor... 

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