Conversion Factors from Chemical Formulas

To complete these steps, we need one additional kind of conversion factor that converts between moles of an element and moles of a compound containing that element. We obtain this conversion factor from the compound s chemical formula. For example, the formula for hexane, C6H14, tells us that each hexane molecule contains six... 

The necessary basic knowledge is provided in Chapter 2 The Chemical Production Plant and its Components. It deals vhth important subdisciplines of technical chemistry such as catalysis, chemical reaction engineering, separation processes, hydrodynamics, materials and energy logistics, measurement and control technology, plant safety, and materials selection. Thus, it acts as a concise textbook vhthin the book that saves the reader from consulting other works when such information is required. A comprehensive appendix (mathematical formulas, conversion factors, thermodynamic data, material data, regulations, etc.) is also provided. 

The solution map begins with moles of calcium carbonate and ends with moles of oxygen. Determine the conversion factor from the chemical formula, which indicates three O atoms for every CaCOs unit. 

To use this relationship, we need mol NaCl, but we have g NaCl. We can, however, use the molar mass of NaCl to convert from g NaCl to mol NaCl. Then we use the conversion factor from the chemical formula to convert to mol Na. Finally, we use the molar mass of Na to convert to g Na. The solution map is ... 

C03-0042. Diagram the process for converting from the mass of a compound of a known chemical formula to the number of atoms of one of its constituent elements. Include all necessary equations and conversion factors. 

The chemical formula for a compound gives the ratio of atoms of each element in the compound to atoms of every other element in the compound. It also gives the ratio of dozens of atoms of each element in the compound to dozens of atoms of every other element in the compound. Moreover, it gives the ratio of moles of atoms of each element in the compound to moles of atoms of every other element in the compound. For example, a given quantity of H2O has 2 mol of H atoms for every mole of O atoms, and a given quantity of CH4 has 1 mol of C atoms for every 4 mol of H atoms. The mole ratio from the formula can be used as a factor to convert from moles of any element in the formula to moles of any other element or to moles of the formula unit as a whole. In Figure 7.2, these additional conversions have been added to those already presented in Figure 7.1. 

You are given 35.6 g AICI3 and must calculate the number of Al + ions, the number of Cl ions, and the mass in grams of one formula unit of AICI3. Molar mass, Avogadro s number, and ratios from the chemical formula are the necessary conversion factors. The ratio of AP+ ions to CE ions in the chemical formula Is 1 3. Therefore, the calculated numbers of ions should be in that ratio. The mass of one formula unit in grams should be an extremely small number. 

To calculate the number of AP+ and Cl ions, use the ratios from the chemical formula as conversion factors. 

This section is designed to fill the gap between the familiar formulas presented above and the assumptions and definitions of terms and physical constants needed to apply them. Values for all physical constants and needed conversion factors are provided, and dimensional analyses are included to show how the final results and their units are obtained. This close focus on the details and units of the equations themselves is followed by worked examples from the chemical literature. The goal is to provide nearly everything the interested reader may need to evaluate his or her own data, with reasonable confidence that he or she is doing so correctly. 

The ratio of moles of P4O10 to moles of P (which came from the subscripts in the chemical formula, P4O10) provided the key conversion factor that allowed us to convert from units of phosphorus to units of tetraphosphorus decoxide. 

Conversions between mass, moles, and the number of particles are summarized in Figure 10.11. Note that molar mass and the inverse of molar mass are conversion factors between mass and number of moles. Avogadros number and its inverse are the conversion factors between moles and the number of representative particles. To convert between moles and the number of moles of atoms or ions contained in the compound, use the ratio of moles of atoms or ions to 1 mole of compound or its inverse, which are shown on the upward and downward arrows in Figure 10.11. These ratios are derived from the subscripts in the chemical formula. 

Draw a solution map showing the conversion from mol H2O to g H2O. The conversion factor is the molar mass of water, which you can determine by summing the atomic masses of all the atoms in the chemical formula. 

V th conversion factors such as titese— which come directly from the chemical formula— we can determine the amoimts of the constituent elements present in a given amount of a compound. 

Notice that we must convert from g NaCl to mol NaQ before we can use the chemical formula as a conversion factor. 

In the previous section, we learned how to calculate mass percent composition from experimental data and how to use mass percent composition as a conversion factor. We can also calculate the mass percent of any element in a compound from the chemical formula for the compound. Based on the chemical formula, the mass... 

Use the molar mass of the compound to convert from grams of the compound to moles of the compound. Then use the chemical formula to obtain a conversion factor to convert from moles of the compound to moles of the constituent element. Finally, use the molar mass of the constituent element to convert from moles of the element to grams of the element. 

These equivalences allow us to determine the amounts of the constituent elements present in a given amount of a compound. For example, suppose we want to know the number of moles of H in 12 moles of HjO. We begin the calculation with the 12 moles of HjO and use the conversion factor obtained from the chemical formula to calculate the moles of H. 

The coefficients in a chemical equation can be used as conversion factors in calculations much as the subscripts in a chemical formula were used previously. These calculations are important because they allow us to predict how much of a particular reactant might be needed in a particular reaction, or how much of a particular product will be formed. For example, one of the gases that contribute to global warming is carbon dioxide (COj). Carbon dioxide is a product of the combustion of fossil fuels such as methane, the primary component of natural gas. From the previous section, the chemical equation for the combustion of methane is as follows ... 

Decide which conversion factors, mathematical formulas, or chemical principles you will need to solve the problem. Your plan might suggest a single calculation or a series of them involving different conversion factor s. Once you understand how you need to proceed, you may wish to sketch out the route you will take, using arrows to point the way from one stage of the solution to the next. Sometimes you will need data that are not actually part of the problem statement For instance, you ll often use data from the periodic table. 

We can see that the relative yield of C molecules depends only on the thermodynamics of coupled reactions. It follows from these formulas that it is practically impossible to reach high conversion factor values if an energyconsuming reaction (2.39) is characterized by a negative value of the standard chemical affinity, = RTln K2 < 0. For example, if s/2 = — 30 kJ/mole (standard affinity for the reaction of ATP synthesis from ADP and Pi), then 2 6 10" and consequently rj 1. This result illustrates why the mechanism of indirect coupling of the two chemical reactions having a common intermediate cannot be efficient. Actually, according to the above-mentioned example, in order to form one molecule C we need to add more than 10 molecules B. 

Notice that we must convert from g CCI2F2 to mol CCI2F2 before we can use the chemical formula as a conversion factor. Always remember that the chemical formula gives us a relationship between the amounts (in moles) of substances, not between the masses (in grams) of them. 

Convert the moles of CO2 and moles of H2O from step 2 to moles of C and moles of H using the conversion factors inherent in the chemical formulas of CO2 and H2O. 

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