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Ch.7 - Thermochemistry
Tro - Chemistry: A Molecular Approach 6th Edition
Tro6th EditionChemistry: A Molecular ApproachISBN: 9780137832217Not the one you use?Change textbook
All textbooksTro 6th EditionCh.7 - ThermochemistryProblem 99
Chapter 7, Problem 99

The citizens of the world burn the fossil fuel equivalent of 7 * 10^12 kg of petroleum per year. Assume that all of this petroleum is in the form of octane (C8H18) and calculate how much CO2 (in kg) the world produces from fossil fuel combustion per year. (Hint: Begin by writing a balanced equation for the combustion of octane.) If the atmosphere currently contains approximately 3 * 10^15 kg of CO2, how long will it take for the world’s fossil fuel combustion to double the amount of atmospheric carbon dioxide?

Verified step by step guidance
1
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) and carbon dioxide (CO2).
Determine the number of moles of octane burned per year using the given mass of octane and its molar mass.
Use the stoichiometry from the balanced equation to find the number of moles of CO2 produced per year.
Convert the moles of CO2 to mass (in kg) using the molar mass of CO2, and calculate how long it will take to double the atmospheric CO2.

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 reacts rapidly with oxygen, producing heat and light. In the case of octane (C8H18), the balanced equation for its combustion is: 2 C8H18 + 25 O2 → 16 CO2 + 18 H2O. This equation shows that burning octane produces carbon dioxide (CO2) and water (H2O), which is essential for calculating the total CO2 produced from the combustion of a given mass of octane.
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Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced equation. It allows us to determine the amount of CO2 produced from a specific mass of octane by using molar ratios derived from the balanced equation. By converting the mass of octane to moles and applying the stoichiometric coefficients, we can find the total mass of CO2 generated during combustion.
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Atmospheric Carbon Dioxide Levels

Understanding the current levels of atmospheric carbon dioxide is crucial for assessing the impact of fossil fuel combustion. The problem states that the atmosphere contains approximately 3 * 10^15 kg of CO2. By calculating the annual CO2 emissions from combustion and comparing it to the current atmospheric levels, we can determine how long it would take for these emissions to double the amount of CO2 in the atmosphere, highlighting the environmental implications of fossil fuel use.
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Related Practice
Textbook Question

Top fuel dragsters and funny cars burn nitromethane as fuel according to the balanced combustion equation: 2 CH3NO2(l) + 3/2O2(g) → 2 CO2(g) + 3 H2O(l) + N2(g) ΔH°rxn = –1418 kJ The enthalpy of combustion for nitromethane is –709.2 kJ/mol. Calculate the standard enthalpy of formation (ΔH°f ) for nitromethane.

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Textbook Question

Determine the mass of CO2 produced by burning enough of each fuel to produce 1.00×102 kJ of heat. a. CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g) ΔH°rxn = –802.3 kJ

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Textbook Question

The explosive nitroglycerin (C3H5N3O9) decomposes rapidly upon ignition or sudden impact according to the balanced equation: 4 C3H5N3O9(l) → 12 CO2(g) + 10 H2O(g) + 6 N2(g) + O2(g) ΔH°rxn = –5678 kJ Calculate the standard enthalpy of formation (ΔH°f ) for nitroglycerin.

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Textbook Question

In a sunny location, sunlight has a power density of about 1 kW/m2. Photovoltaic solar cells can convert this power into electricity with 15% efficiency. If a typical home uses 385 kWh of electricity per month, how many square meters of solar cells are required to meet its energy requirements? Assume that electricity can be generated from the sunlight for 8 hours per day.

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Textbook Question

The kinetic energy of a rolling billiard ball is given by KE = 1/2 mv2. Suppose a 0.17-kg billiard ball is rolling down a pool table with an initial speed of 4.5 m/s. As it travels, it loses some of its energy as heat. The ball slows down to 3.8 m/s and then collides head-on with a second billiard ball of equal mass. The first billiard ball completely stops and the second one rolls away with a velocity of 3.8 m/s. Assume the first billiard ball is the system. Calculate q.

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