Gram-atomic mass

Chemists may distinguish between the molar masses of pure elements, molecular compounds, and ionic compounds by referring to them as the gram atomic mass, gram molecular mass, and gram formula mass, respectively. Don t be fooled The basic concept behind each term is the same molar mass. 

CH O. For the sake of simplicity, assume that you have a total of 100 g of this mystery compound. Therefore, you have 40.0 g of Ccirbon, 6.7 g of hydrogen, and 53.3 g of oxygen. Convert each of these masses to moles by using the gram atomic masses of C, H, and O ... 

H O. First, assume that you have 88.9 g of oxygen and 11.1 g of hydrogen in a 100 g Scimple. Then convert each of these masses into moles by using the gram atomic masses of oxygen and hydrogen ... 

Because you know that 1 mol of electrons can create 1 mol of sodium metal, this translates to 0.84 mol Na(s) produced. All that remains is to convert this value to grams using the gram atomic mass (see Chapter 7 for details) ... 

Convert 2.80 mol Na(s) to grams by using the gram atomic mass ... 

Mole is abbreviated mol. Do not use m or M for mole these symbols are used for other quantities related to moles, and so you will be confused if you use either of them. Note A mole is referred to by some authors as a gram molecular mass because 1 mol of molecules has a mass in grams equal to its molecular mass. In this terminology, a gram atomic mass is 1 mol of atoms, and a gram formula mass is 1 mol of formula units. 

Work done against gravity may be handled in two distinct ways. The first is to consider a material with n moles of gram atomic mass M being lifted through a height dz the element of work done on the system is... 

Occasionally, one encounters gram-atomic mass (GAM), gram-formula mass (GFM), and gram-molecular mass (GMM). These terms are functionally the same as molar mass. For example, the GAM of an element is the mass in grams of a sample containing atoms and is equal to the element s atomic... 

One gram-atom (or pound-atom) is the mass in grams (or pounds) of a given element that is numerically equal to its atomic weight. Thus, the number of gram-atoms of an elementary substance is m/A, where m is the mass (in grams) and A, its atomic weight. 

One molecule (or mole) of propane reacts with five molecules (or moles) of oxygen to produce three molecules (or moles) or carbon dioxide and four molecules (or moles) of water. These numbers are called stoichiometric coefficients (v.) of the reaction and are shown below each reactant and product in the equation. In a stoichiometrically balanced equation, the total number of atoms of each constituent element in the reactants must be the same as that in the products. Thus, there are three atoms of C, eight atoms of H, and ten atoms of O on either side of the equation. This indicates that the compositions expressed in gram-atoms of elements remain unaltered during a chemical reaction. This is a consequence of the principle of conservation of mass applied to an isolated reactive system. It is also true that the combined mass of reactants is always equal to the combined mass of products in a chemical reaction, but the same is not generally valid for the total number of moles. To achieve equality on a molar basis, the sum of the stoichiometric coefficients for the reactants must equal the sum of v. for the products. Definitions of certain terms bearing relevance to reactive systems will follow next. 

This reasoning is readily extended to other elements. A sample of any element with a mass in grams equal to its atomic mass contains the same number of atoms, NA, regardless of the identity of the element. 

The importance of Avogadro s number in chemistry should be clear. It represents the number of atoms of an dement in a sample whose mass in grams is numerically equal to die atomic mass of the dement. Thus there are... 

To anticipate some of the results to be presented later, it is instructive to compute the equilibrium compn ofPETN at 1600°K. PETN is nearly oxygen-balanced and as will be shown later its Tfr- 1600°K. The empirical formula for PETN is CgHs On. Let X be the number of moles of C03 at equilibrium, and C, H, O the original gram atoms of carbon, hydrogen and oxygen respectively. Then from mass balance and Raoult s law... 

The mass of an atom in terms of the atomic mass constant is numerically the same as the molar mass in grams per mole. For instance, the molar mass of carbon-12 is exactly 12 g-mol, and the mass of a carbon-12 atom is exactly 12mu. 

Water soluble protein with a relative molecular mass of ca. 32600, which particularly contains copper and zinc bound like chelate (ca. 4 gram atoms) and has superoxide-dismutase-activity. It is isolated from bovine liver or from hemolyzed, plasma free erythrocytes obtained from bovine blood. Purification by manyfold fractionated precipitation and solvolyse methods and definitive separation of the residual foreign proteins by denaturizing heating of the orgotein concentrate in buffer solution to ca. 65-70 C and gel filtration and/or dialysis. 

The activation energy for evaporation of over-stechiometric zinc atoms Zn calculated from the tilt of this line is 32 kcal/gram/atom. This means that evaporation heat of superstechiometric zinc atoms (Zn ) from zinc oxide found in these experiments agrees well with the corresponding value found in [31] by mass-spectrometry. 

The formula weight of a substance is equal to its number of grams per mole. Avogadro s number is the number of atomic mass units in 1 g. It is defined in that manner so that the atomic weight of an element (in amu) is numerically equal to the number of grams of the element per mole. Consider helium, with atomic weight 4.0 ... 

Avogadro s number a mole 6.02 X 1023 units the number of atomic mass units per gram. 

One mole of atoms of an element is its relative atomic mass expressed in grams. 

Calculate the mass, in grams, of each of the following amounts (relative atomic masses are given in brackets) ... 

The behaviour of electrons in metals shows the translational properties of quantum particles having quantized energy levels. These cannot be approximated to the continuous distribution describing particles in a gas because of the much smaller mass of the electron when compared with atoms. If one gram-atom of a metal is contained in a cube of length L, the valence electrons have quantum wavelengths, X, described by the de Broglie equation... 

In these problems we use the Avogadro constant and the fact that one mole of atoms of an element has a weight in grams equal to its atomic mass. 

Our modern model describes the atom as an electrically neutral sphere with a tiny nucleus in the center containing positively charged protons and neutral neutrons. The negatively charged electrons are moving in complex paths outside the nucleus in energy levels at different distances from the nucleus. These subatomic particles have very little mass expressed in grams so we often use the unit of an atomic mass unit (amu or simply u). An amu is 1/12 the mass of a carbon atom that contains six protons and six neutrons. Table 2.1 summarizes the properties of the three subatomic particles. 

The substance s molar mass is the mass in grams of the substance that contains one mole of that substance. In the previous chapter, we described the atomic mass of an element in terms of atomic mass units (amu). This was the mass associated with an individual atom. At the microscopic level, we can calculate the mass of a compound by simply adding together the masses in amu s of the individual elements in the compound. However, at the macroscopic level, we use the unit of grams to represent the quantity of a mole. 

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