Chemical formula composition

Substance Chemical formula composition Gas concentration c (% (v/v)) MESG mm... 

To this point, our study of chemistry has been largely qualitative, involving very few calculations. However, chemistry is a quantitative science. Atoms of elements differ from one another not only in composition (number of protons, electrons, neutrons), but also in mass. Chemical formulas of compounds tell us not only the atom ratios in which elements are present but also the mass ratios. 

About 95% of Escherichia coli is C, H, O and N. The chemical formula for cell composition and the stoichiometric coefficients in (9.2.1) depend on media composition and the environment surrounding die cell.2,4 All die major elements in die above equation have to be balanced. Then die stoichiometric coefficients are identified by solving simultaneously the system of equations ... 

The chemical formula of a compound represents its composition in terms of chemical symbols. Subscripts show the numbers of atoms of each element present in the smallest unit that is representative of the compound. For molecular compounds, it is common to give the molecular formula, a chemical formula that shows how many atoms of each type of element are present in a single molecule of the compound. For instance, the molecular formula for water is H20 each molecule contains one O atom and two H atoms. The molecular formula for estrone, a female sex hormone, is Clgl-I2202, showing that a single molecule of estrone consists of 18 C atoms, 22 FI atoms, and 2 O atoms. A molecule of a male sex hormone, testosterone, differs by only a few atoms its molecular formula is (lyH2802. Think of the consequences of that tiny difference ... 

If the chemical formula of a compound is already known, its mass percentage composition can be obtained from the formula. 

In a balanced chemical equation (commonly called a chemical equation ), the same number of atoms of each element appears on both sides of the equation, chemical equilibrium A dynamic equilibrium between reactants and products in a chemical reaction, chemical formula A collection of chemical symbols and subscripts that shows the composition of a substance. See also condensed structural formula empirical formula,- molecular formula structural formula. 

A chemical formula describes the composition of a substance by giving the relative numbers of atoms of each element. When a substance contains discrete molecules, a chemical formula is also a molecular formula. A chemical formula contains elemental symbols to represent atoms and subscripted numbers to indicate the number of atoms of each type. The simplest chemical formulas describe pure elements. The chemical formulas of most elements are their elemental symbols helium is He, silicon is Si, copper is Cu. However, seven elements occur naturally as diatomic molecules (Figure 3-lT so their chemical formulas take the form X2 A few other elements occur as atomic clusters, notably P4 and Sg. ... 

Just as each element has a characteristic molar mass, so does every chemical compound. Chemical compounds are composed of atoms bound together into molecules or ions clustered together in electrically neutral aggregates. In either case a chemical formula describes the atomic composition of a compound. 

The chemical formula of a compound contains essential information about its composition. The formula identifies which elements are present, and it states the number of atoms of each kind present in one unit of the compound. We need the chemical formula of a substance to calculate its molar mass. In fact, almost all chemical calculations require the correct chemical formula. How are chemical formulas determined in the first place ... 

We illustrate how the mass percent composition of a compound is related to its chemical formula using ammonium nitrate (NH4 NO3). The molar masses of NH4 NO3 and its constituent elements can be used to convert the chemical formula into mass percentages. 

The elemental analysis of a compound is usually determined by a laboratory that specializes in this technique. A chemist who has prepared a new compound sends a sample to the laboratory for analysis. The laboratory charges a fee that depends on the type and number of elements analyzed. The results are returned to the chemist as a listing of mass percent composition. The chemist must then figure out which chemical formula matches this composition. If a chemist has reason to expect a particular chemical formula, the observed percentages can be matched against the calculated percentages for the expected formula. This process is illustrated in Example 3-13. 

C03-0030. One of the major iron ores is an oxide with the following percentage composition Fe, 72.36% and O, 27.64%. What is the chemical formula of this ore ... 

Some mineral products are employed essentially in the form in which they are mined, with only shaping, crushing, cleaning or other treatments that do not change their compositions. Coal, in most of its uses, is a typical example. Most minerals are processed, however, to yield usable products - metals, chemicals or other materials from which most of the items of utility are derived. As regards coal, it may be pointed out that it is often referred to as a mineral, but unlike a true mineral, it has no fixed chemical formula. 

Thus, in weak electrolytes, molecules can exist in a similar way as in non-electrolytes—a molecule is considered to be an electrically neutral species consisting of atoms bonded together so strongly that this species can be studied as an independent entity. In contrast to the molecules of non-electrolytes, the molecules of weak electrolytes contain at least one bond with a partly ionic character. Strong electrolytes do not form molecules in this sense. Here the bond between the cation and the anion is primarily ionic in character and the corresponding chemical formula represents only a formal molecule nonetheless, this formula correctly describes the composition of the ionic crystal of the given strong electrolyte. 

Thus, three types of components can be distinguished in most substances, whether of natural origin or made by humans major, minor, and trace components (see Table 8). The major components, also known as the main or matrix components, are those that determine the chemical nature and properties of a substance. The major components occur in the substance in high concentration, generally exceeding 1 % of the total weight. In minerals and biological substances, for example, the major components are those that appear in the chemical formula that expresses their composition. 

The carbohydrates are substances made by green plants from carbon dioxide that they extract from the air and from water absorbed from the soil. The term carbohydrate is derived from the chemical formulas of the compounds, which can be written so as to express their composition in terms of atoms of carbon combined with molecules of water the formula for sucrose (table sugar), for example, is C12H22011f but it can also be written as C12(H20)ll, indicating that the molecule consists of 11 molecules of water... 

TRADE NAME SUPPLIER CHEMICAL FORMULA OF MAJOR SYNTHESISED PRODUCT % SURFACTANT ACTIVITY NATURE OF SURFACTANT COMPOSITION INORGANIC SALT CONTENT/ WATER CONTENT/ ... 

The chemical composition of the macular yellow pigment was originally characterized by Wald as being a leaf xanthophyll carotenoid (Wald 1945). It took another 40 years until the molecules lutein and zeaxanthin were identified as its main constituents by Bone et al. (1985), and in 1993 the same authors reported that macular zeaxanthin is itself comprised of two stereoisomers, (3/f,37f)-/eaxan(hin and (3/f,3. S )-/eaxan(hin (Bone et al. 1993), this compound will be called (meso)-zeaxanthin throughout this article. These three molecules are often collectively called the macular xanthophylls (for their chemical formulas see Figure 13.2). 

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