Composition of the Substance

Land disposal sites result in soil contamination through leachate migration. The composition of the substances produced depends principally on the type of wastes present and the decomposition in the landfill (aerobic or anaerobic). The adjacent soil can be contaminated by direct horizontal leaching of surface runoff vertical leaching and transfer of gases from decomposition by diffusion and convection. The disposal of... 

A coordination compound is usually synthesized from a transition metal ion that is in solution. The compound is filtered from the solution and tested in various ways to determine the composition of the substance. (See the Reactions and Periodicity chapter.)... 

Vapor density is a physical property of major importance to fire protection. Because the vapor density varies with the total weight of all the atoms in a molecule of the vapor of a substance, if the chemical composition of the substance comprising the vapor is known, then the weight or density of its vapor when compared to air can be determined as in the following relationship ... 

Articles differ from preparations or substances by the fact that they have a specific form or surface. The function of the product is determined by this form (e g. sheets of floor covering) and less so by the composition of the substance (e.g. polymers and additives). 

The first compound of the ammino-rhodium series examined was chloro-pentammino-rhodium chloride, [Rh(NH3)5Cl]Cl2, which vras prepared by treating rhodium trichloride with ammonia. Claus 1 investigated the composition of the substance and prepared from it, by means of moist silver oxide, a strongly basic substance, which proved to be the corresponding hydroxide, [Rh(NH3)5Cl](OH)2. 

Sublimation. Perform the experiment in a fume cupboard ) Put the beryllium oxyacetate crystals into a test tube. Slightly tilt the tube with its mouth downward and carefully heat it in the flame of a burner. What happens What is the composition of the substance deposited on the tube walls Examine the crystals of the precipitated and sublimed beryllium oxyacetate under a microscope. What can this compound be used for in the technology of beryllium ... 

Put a small amount of the magnesium chloride hexahydrate into a crucible and roast it. What is observed Decompose the salt completely. How can you see that this has occurred Cool the crucible and add 1-2 ml of water. What is the composition of the substance that has not dissolved in the water ... 

C. What is the appearance and composition of the substance Write the equation of the reaction. 

The brilliant Frenchman s legacy will be with us forever. Traite Elementaire de Chimie was the world s first real chemistry text. In it Lavoisier introduced a whole new system of nomenclature, which we still use. No longer would chemists refer to oil of vitriol or flowers of zinc. Instead they adopted names like sulfuric acid and zinc oxide, names that reflected the actual composition of the substances in question. Lavoisier clearly defined elements as substances that could not be broken down further by chemical means. Chemistry was evolving into an organized science ... 

The formula HCI04 H20 is a way of specifying the composition of the substance when we are ignorant of its structure. A more accurate formula would be H30+C104. 

There are also many ways substances can be changed without a chemical reaction taking place and changing the chemical composition of the substance. These changes are called physical changes. 

A physical property of a substance is a property that can be observed and measured without altering the composition of the substance. 

Spectroscopy is another method used to detect art forgeries. In spectroscopy, electromagnetic radiation is applied to the substance or substances under consideration. The resulting spectra are recorded to identify the chemical composition of the substance or substances. When a spectrophotometer is used, the radiation, usually visible and invisible ultraviolet waves, can be applied to a solution in a tube, and the absorption of radiation is noted. For this type of analysis, a spectrophotometer must be available. 

When SP [T] = SP"[0] (condition 2), AS°[T] can be expressed as v (SP [T] — Sp"[0]) that is, in terms of the observed quantities. We use the difference (Sp [T] — SP"[0]) as the absolute value of the entropy, which is equivalent to assigning the value of zero to SP"[0]. The two effects for which this assignment is valid are (1) the nuclear effects including those of nuclear spin, provided that the isothermal change of state does not involve a nuclear reaction and (2) the isotopic effects, provided there is no change in the isotopic composition of the substances. 

The amount of oxygen required for oxidizing a substance to carbon dioxide and water may be sto-ichiometrically calculated if the chemical composition of the substance is known. In contrast, the... 

What happens with water also happens with many other substances. Changing states does not alter the chemical composition of the substance. For example when you cool oxygen gas (O ) to very low temperatures, it becomes liquid oxygen that is composed of molecules. The only difference between liquid and gaseous oxygen is how strongly the molecules are held together. 

The constant of integration i, which depends on the composition of the substance, is caUed the vapour pressure constant or the chemical constant ( 10. VIIIL). 

The law of constant proportions was enunciated by the French chemist Joseph Louis Proust (1754-1826) in 1799. For several years it was attacked vigorously by Claude Louis Bertholet (1748-1822), who contended that the composition of the compound depended on the way in which it was prepared. Proust defended the law by pointing out that the materials described by Bertholet as exceptions were mixtures (of different lead oxides, of mercurous salts and mercuric salts, etc.) or solutions. Accurate data showing constancy of composition of the substances investigated to 1 part in 100,000 were first reported by the Belgian chemist J. S. Stas in 1865. 

Molybdenum Oxide (Blue), MOjOg ( ) or MOgO ( ).—If a suspension of molybdenum trioxide in water be heated on a water-bath with a large excess of pow dered molybdenum, a blue solution is obtained, containing, it is supposed, unpolymerised molecules of the compound MogOg but it is by no means certain either that this formula represents the actual composition of the substance, or that there is but one blue oxide of molybdenum. On addition of certain salts polymerisation is considered (Dumanski) to take place, and the oxide passes to the colloid form. 

The degree of supersaturation of the mother liquor or difference in concentration of solute on opposite sides of a growing crystal influences crysfal habif. The effecl of supersaturation on the change in habit was described by an equation, yjx = kAG", where y/x is the ratio of crystal length to breadth, k is a coefficient of proportionality depending on diffusion, AG is the degree of supersaturation (moles/1000 mol of solvent at the moment of nuclei formation), and n is a number that depends on the crystallographic classification and the chemical composition of the substance. 

Previous to the last decade most of the research on the group dealt with the composition of the substances. There still remains an enormous amount of this work to be done. Now, however, emphasis is shifting to a study of the structure and molecular size of these bodies. The methods that were developed in the study of the simple sugars, the glycosides, starch and cellulose are being applied in the study of the polyuronides. 

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