Formula mass types

The three types of formula masses correspond to the three types of formula units (1) atomic masses (also called atomic weights), (2) molecular masses (also called molecular weights), and (3) formula masses for ionic compounds (also called formula weights). The term atomic mass may be used whether an atom is combined or not, but it always refers to the mass of one atom of an element. 

The formula mass (formula weight) of a substance is determined by adding the atomic masses (atomic weights) of each atom (not each element) in a formnla unit. Molecular mass is one type of formula mass (for substances that form molecnles) and is calculated in the same way as the formula mass for an ionic compound. For example, the formula mass of NH3 is 17.0 amu, the atomic mass of three hydrogen atoms plus that of one nitrogen atom. Three or more significant digits should be used to report formula masses. (Section 7.1)... 

FIGURE 8.5 Schematic view of a pathway container. The parent structnre is the starting point for metabolic investigations. From there, several metabolites are identified in different species and tissues. Each connector stores the type of relationship between metabolites together with information about the route of transformation. Each metabolite includes administrative data (e.g., name, identifier), molecular metadata such as residue information, structure metadata (e.g., formula, mass), and links to records of experimental data obtained for the structure. 

Calculate the formula mass of (a) (NH4)2HP04 (one type of fertilizer) (b) C2H5OH (ethyl alcohol) (c) P4 (one form of elemental phosphorus). 

Chemical formulas describe the simplest atom ratio (empirical formula), actual atom number (molecular formula), and atom arrangement (structural formula) of one unit of a compound. An ionic compound is named with cation first and anion second. For metals that can form more than one ion, the charge is shown with a Roman numeral. Oxoanions have suffixes, and sometimes prefixes, attached to the element root name to indicate the number of oxygen atoms. Names of hydrates give the number of associated water molecules with a numerical prefix. Acid names are based on anion names. Covalent compounds have the first word of the name for the element that is leftmost or lower down in the periodic table, and prefixes show the number of each atom. The molecular (or formula) mass of a compound is the sum of the atomic masses in the formula. Molecules are depicted by various types of formulas and models. 

The chemical action of petroleum products on organisms depends on their chemical composition, which is in turn dependent on the type of petroleum, on the method of its treatment, on the distillation fraction and also on any additives. Petroleum itself contains about 100 different chemical compounds. They are characterized by different solubilities — benzene derivatives are water-soluble up to a concentration of approximately 100 mg 1, naphthalenes up to about 30 mg 1 and hydrocarbons with a higher formula mass are water-insoluble. The solubility increases the hazardous character of toxic substances. In general, petroleum products are only slowly degraded biologically and it is highly probable that the most toxic substances are decomposed most slowly and the products of their degradation can be even more harmful than the initial substances [4]. 

The MassBank records have one-to-one relation to a specific mass spectrum. Each record has specific information like accession number, record file, license, and author apart from iirformation on the chemical compound regarding its formula, mass, smiles, InChl identifier etc. The analytical information available is the instrument type and make, Msn type data. A typical MassBank record is shown here (Fig. 7.28). 

One mole of a compound contains Avogadro s number of formula units of that compound. The terms molecular weight, molecular mass, formula weight, and formula mass have been used in the past to refer to the mass of 1 mol of a compound. However, the term molar mass is more inclusive, because it can be used for all types of compounds. 

The formula mass is the sum of the atomic masses of all the atoms in the chemical formula. In determining the number of each type of atom, don t forget to multiply subscripts inside parentheses by subscripts outside parentheses. 

Explain the difference between the terms molecular mass and formula mass. To what type of compound does each term refer ... 

Separation of families by merely increasing the resolution evidently can not be used when the two chemical families have the same molecular formula. This is particularly true for naphthenes and olefins of the formula, C H2 , which also happen to have very similar fragmentation patterns. Resolution of these two molecular types is one of the problems not yet solved by mass spectrometry, despite the efforts of numerous laboratories motivated by the refiner s major interest in being able to make the distinction. Olefins are in fact abundantly present in the products from conversion processes. 

As you will see shortly, the formula of a compound can be used to determine the mass percents of the elements present. Conversely, if the percentages of the elements are known, the simplest formula can be determined. Knowing the molar mass of a molecular compound, it is possible to go one step further and find the molecular formula. In this section we will consider how these three types of calculations are carried out. 

The most complex problem of this type requires you to determine the simplest formula of a compound given only the raw data obtained from its analysis. Here, an additional step is involved you have to determine the masses of the elements present in a fixed mass of the compound (Example 3.6). 

Mole-mass, 55,70-72q Molecular formula A formula in which the number of atoms of each type in a molecule is indicated as a subscript after the symbol of the atom, 34,59-60 Molecular geometry The shape of a molecule, describing the relative positions of atoms, 175 193q electron pairs, 179t major features, 175-176 molecules with expanded octets, 181t molecules with unshared electron pairs, 181t... 

Compilations of Reference Spectra There are several compilations of reference mass spectra available of which the oldest is the American Petroleum Institute (Ref 82) collection of spectra obtained mostiy on the older type instruments. Recent collections index spectra variously, eg, under reference number (Ref 19). molecular weight (Refs 12 19), molecular formula (Ref 19), fragment ion values (Ref 19), and base peak (Refs 12 19). A quarterly journal, Archives of Mass Spectral Data ... 

To convert the mass percentage composition obtained from a combustion analysis into an empirical formula, we must convert the mass percentages of each type of atom into the relative numbers of atoms. The simplest procedure is to imagine that we have a sample of mass 100 g exactly. That way, the mass percentage... 

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. 

Achieving high resolving power and high m/z measurement accuracy is one way of decreasing uncertainty when the determination of unknown analyte identity is the object of an experiment. But like many techniques, an increase in experimental or interpretive confidence does not come without some cost (e.g., instrument size, complexity, price, etc.). However, exact m/z measurements (and their associated elemental formula information) are but one type of information that can be derived from mass spectrometers. In the sections that follow, a variety of mass analyzers will be described in terms of their basic principles, functionality and applications. 

The Law of Conservation of Mass states that the total mass remains unchanged. This means that the total mass of the atoms of each element represented in the reactants must appear as products. In order to indicate this, we must balance the reaction. When balancing chemical equations, it is important to realize that you cannot change the formulas of the reactants and products the only things you may change are the coefficients in front of the reactants and products. The coefficients indicate how many of each chemical species react or form. A balanced equation has the same number of each type of atom present on both sides of the equation and the coefficients are present in the lowest whole number ratio. For example, iron metal reacts with oxygen gas to form rust, iron(III) oxide. We may represent this reaction by the following balanced equation ... 

Sulfosuccinates, as presented with their general structural formula in Fig. 2.11.33, are applied as surfactants for personal hygiene because of their hypoallergenic features. The sodium salt of the sulfosuccinate blend with the formula ROOC-CH-(SC>3 )-CH2-COOR Na+ (R = CsH-iy) was examined by APCI-FIA-MS in the positive and negative modes. The addition of an excess of ammonium acetate under FIA-APCI-MS(+) conditions resulted in [M — NH4]+ ions with mlz 440 while [M — H] ions with mlz 421, however, were observed in the negative APCI-FIA-MS mode (Fig. 2.11.34(a)). Only one type of ion could be observed in this industrial blend by FIA-MS. This purity could also be confirmed by APCI-LC-MS(-), as shown in the total ion current trace (cf. Fig. 2.11.34(b)), which is presented in combination with the averaged mass spectrum under the signal in the inset of Fig. 2.11.34(b) [22],... 

Fig. 2.12.6. Identification of esterquat compounds FIA-APCI-MS-MS(+) (CID) product ion mass spectrum of selected [M — RCO]+ base peak ion of cationic surfactant blend of di-hydrogenated tallowethyl hydroxyethyl ammonium methane sulfate type (mlz 692 general formula (R(C0)0CH2CH2)2-N (CH3)-CH2CH2(0H)CH30S03) fragmentation behaviour under CID...

Fig. 2.12.15. FIA-APCI-MS-MS(+) (CID) product ion mass spectrum of cationic surfactant compound (m/z 538) fatty acid polyglycol amine type observed in the Saale river, Germany (general formula R—N H((CH2—CH2—OH)x)—(CH2—CH2—OH)y X fragmentation behaviour of [M]+ parent ion at m/z 538 under CID conditions is presented...

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