Gas stoichiometry molar volume method

In Section 10.2 you learned how to calculate the mass of one species in a chemical reaction with a known equation from a given mass of another species in three steps that we called a stoichiometry path (1) Convert the mass of the given species to moles (2) from the chemical equation, convert the moles of given species to moles of wanted species (3) convert the moles of wanted species to grams. In this section, you have learned how to solve the same problem if the given and/or wanted species is the volume of a gas at STP. In Section 14.7 or 14.8 you will learn how to solve the problem if the given and/or wanted species is the volume of the gas at nonstandard conditions. 

Gas Stoichiometry Option The next two sections offer alternative ways to solve gas stoichiometry problems at given temperatures and pressures. 

In the molar volume method, the ideal gas equation is solved for the molar volume at the given temperature and pressure. The calculated molar volume is then used to solve the problem by the three steps in the stoichiometry path, just as 22.4 L/mol is used to solve a problem at STP. All problems are solved in the same way. The section describing the molar volume method is identified by a tan bar in the inside margin, as next to this paragraph. 

Your instructor will probably assign one section and tell you to skip the other. If you must choose between the sections, we suggest that you compare the examples and end-of-book answers for both methods—the same problems are used—and choose the one that looks best for you. Answers for the molar volume method are printed over a tan background and ideal gas equation answers are printed over a green background. Whether your instructor chooses or you do, we recommend that you learn one method and disregard the other. 

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Gas Stoichiometry Molar Volume Method Gas Stoichiometry Ideal Gas Equation Method Volume-Volume Gas Stoichiometry... 

Between this chapter and Chapter 10, we have now seen three different ways to convert between a measurable property and moles in equation stoichiometry problems. The different paths are summarized in Figure 13.10 in the sample study sheet on the next two pages. For pure liquids and solids, we can convert between mass and moles, using the molar mass as a conversion factor. For gases, we can convert between volume of gas and moles using the methods described above. For solutions, molarity provides a conversion factor that enables us to convert between moles of solute and volume of solution. Equation stoichiometry problems can contain any combination of two of these conversions, such as we see in Example 13.8. 

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