Textbook Question
Find the percent by mass of sodium chloride in a 1.35 M NaCl solution. The density of the solution is 1.05 g/mL.
Ch.4 - Chemical Quantities & Aqueous Reactions
Chapter 4, Problem 105
The combustion of gasoline produces carbon dioxide and water. Assume gasoline to be pure octane (C8H18) and calculate the mass (in kg) of carbon dioxide that is added to the atmosphere per 1.0 kg of octane burned. (Hint: Begin by writing a balanced equation for the combustion reaction.)
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Write the balanced chemical equation for the combustion of octane: \(2 \text{C}_8\text{H}_{18} + 25 \text{O}_2 \rightarrow 16 \text{CO}_2 + 18 \text{H}_2\text{O}\).
Calculate the molar mass of octane (C8H18) using the atomic masses of carbon (C) and hydrogen (H).
Determine the number of moles of octane in 1.0 kg by dividing the mass of octane by its molar mass.
Use the stoichiometry of the balanced equation to find the moles of CO2 produced per mole of octane burned.
Calculate the mass of CO2 produced by multiplying the moles of CO2 by its molar mass, and convert the result to kilograms.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Combustion Reaction
A combustion reaction is a chemical process in which a substance (typically a hydrocarbon) reacts with oxygen to produce carbon dioxide and water, releasing energy. For octane (C8H18), the balanced equation for its complete combustion is C8H18 + 12.5 O2 → 8 CO2 + 9 H2O. Understanding this reaction is crucial for determining the products and their quantities when octane is burned.
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Combustion Apparatus
Stoichiometry
Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced equation. It allows us to determine the mass of products formed from a given mass of reactants. In this case, stoichiometry will help calculate the mass of carbon dioxide produced from burning 1.0 kg of octane by using molar ratios derived from the balanced combustion equation.
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Molar Mass
Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). For octane (C8H18), the molar mass is approximately 114.22 g/mol. Knowing the molar mass is essential for converting between mass and moles, which is necessary for applying stoichiometry to find the mass of carbon dioxide produced from the combustion of octane.
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Related Practice
Textbook Question
Many home barbeques are fueled with propane gas (C3H8). What mass of carbon dioxide (in kg) is produced upon the complete combustion of 18.9 L of propane (approximate contents of one 5-gallon tank)? Assume that the density of the liquid propane in the tank is 0.621 g/mL. (Hint: Begin by writing a balanced equation for the combustion reaction.)
Textbook Question
Aspirin can be made in the laboratory by reacting acetic anhydride (C4H6O3) with salicylic acid (C7H6O3) to form aspirin (C9H8O4) and acetic acid (C2H4O2). The balanced equation is: C4H6O3 + C7H6O3 → C9H8O4 + C2H4O2 In a laboratory synthesis, a student begins with 3.00 mL of acetic anhydride (density = 1.08 g/mL) and 1.25 g of salicylic acid. Once the reaction is complete, the student collects 1.22 g of aspirin. Determine the limiting reactant. Determine the theoretical yield of aspirin. Determine the percent yield for the reaction.
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Textbook Question
The combustion of liquid ethanol (C2H5OH) produces carbon dioxide and water. After 4.62 mL of ethanol (density = 0.789 g/mL) is allowed to burn in the presence of 15.55 g of oxygen gas, 3.72 mL of water (density = 1.00 g/mL) is collected. Determine the percent yield for the reaction. (Hint: Write a balanced equation for the combustion of ethanol.)
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