Chemical quantities mass mole conversions

Chemical stoichiometry is the area of study that considers the quantities of materials in chemical formulas and equations. Quite simply, it is chemical arithmetic. The word itself is derived from stoicheion, the Greek word for element and metron, the Greek word for measure. When based on chemical formulas, stoichiometry is used to convert between mass and moles, to calculate the number of atoms, to calculate percent composition, and to interpret the mole ratios expressed in a chemical formula. Most topics in chemical arithmetic depend on the interpretation of balanced chemical equations. Mass/mole conversions, calculation of limiting reagent and percent yield, and various relationships among reactants and products are commonly included in this topic area. 

The balanced equation expresses quantities in moles, but it is seldom possible to measure out quantities in moles directly. If the quantities given or required are expressed in other units, it is necessary to convert them to moles before using the factors of the balanced chemical equation. Conversion of mass to moles and vice versa was considered in Sec. 4.5. Here we will use that knowledge first to calculate the number of moles of reactant or product, and then use that value to calculate the number of moles of other reactant or product. 

Figure 3.8 Summary of the mass-mole-number relationships in a chemical reaction. The amount of one substance in a reaotion is related to that of any other. Quantities are expressed in terms of grams, moles, or number of entities (atoms, molecules, or formula units). Start at any box in the diagram (known) and move to any other box (unknown) by using the information on the arrows as conversion factors. As an example, if you know the mass (in g) of A and want to know the number of molecules of B, the path involves three calculation steps ...

Conversions of moles of one substance to moles of any other in the balanced chemical equation is straightforward just remember that it is moles not mass that is related to the coefficients in the equation, ffowever, stoichiometry problems often give students more trouble than they should because the problems are often asked in terms of masses or other quantities that can be related to moles of reactant or product. These problems are multistep problems, but should not present too much difficulty because each individual step is straightforward. 

We ve seen the importance of the concept of the mole when dealing with chemical reactions involving macroscopic quantities of material. But generally it is not possible to measure the number of moles in a sample directly because that would imply that we can count molecules. Molar masses provide a crucial connection and allow us to convert from masses, which can be measured easily, to numbers of moles. The mass and the number of moles are really just two different ways of expressing the same information—the amount of a substance present. The molar mass functions much like a unit conversion between them, allowing us to go from... 

The Chemkin gas-phase subroutine library provides the evaluation of information about species, reactions, gas constants and units, equations of state, mole-mass conversion, thermodynamic properties, chemical production rates, equilibrium constants, rate of progress variables, and sensitivity parameters, along with the appropriate derivatives of the above quantities. 

The Per relationship in molar mass, grams per mole, means you can use dimensional analysis to convert from grams to moles or from moles to grams. Molar mass is the conversion factor. This one-step conversion is probably used more often than any other conversion in chemistry because we measure quantities on the macroscopic level in grams. However, chemical reactions take place on the particulate level, and moles are units that express the number of particles. 

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