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Ch.3 - Chemical Reactions and Reaction Stoichiometry
Chapter 3, Problem 68d

The complete combustion of octane, C8H18, a component of gasoline, proceeds as follows: 2 C8H18(l) + 25 O2(g) → 16 CO2(g) + 18 H2O(g). (d) How many grams of CO2 are produced when 15.0 gal of C8H18 are combusted? (d) How many grams of CO2 are produced when 15.0 gal of C8H18 are combusted?

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1
First, convert the volume of octane from gallons to liters using the conversion factor: 1 gallon = 3.78541 liters.
Next, calculate the mass of octane in grams. Use the density of octane, which is approximately 0.703 g/mL, to convert the volume in liters to mass in grams.
Determine the number of moles of octane (C8H18) using its molar mass. The molar mass of C8H18 is calculated by adding the atomic masses of carbon and hydrogen: (8 * 12.01 g/mol for C) + (18 * 1.008 g/mol for H).
Use the stoichiometry of the balanced chemical equation to find the moles of CO2 produced. According to the equation, 2 moles of C8H18 produce 16 moles of CO2. Use this ratio to calculate the moles of CO2 from the moles of C8H18.
Finally, convert the moles of CO2 to grams using the molar mass of CO2, which is 44.01 g/mol. Multiply the moles of CO2 by this molar mass to find the mass of CO2 produced.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It allows us to calculate the amounts of substances consumed and produced in a reaction based on balanced chemical equations. In this case, stoichiometry will help determine how many grams of CO2 are produced from a given volume of octane.
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Molar Volume of a Gas

The molar volume of a gas at standard temperature and pressure (STP) is approximately 22.4 liters per mole. This concept is essential for converting between the volume of gaseous reactants or products and the number of moles, which can then be used in stoichiometric calculations. Understanding this relationship is crucial for determining how many moles of CO2 are produced from the combustion of octane.
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Density and Conversion Factors

Density is the mass per unit volume of a substance, typically expressed in grams per milliliter (g/mL) for liquids. To convert the volume of octane (in gallons) to grams, one must use the density of octane, which allows for the calculation of mass from volume. This conversion is necessary to find out how many grams of CO2 are produced from the combustion of the specified volume of octane.
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