Domanda del libro di testo
Ethanol (C2H5OH) is blended with gasoline as an automobile fuel. (d) Calculate the mass of CO2 produced per kJ of heat emitted.
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Ch.5 - Thermochemistry
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970
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TOC.tableOfContents
- Ch.1 - Introduction: Matter, Energy, and Measurement146
- Ch.2 - Atoms, Molecules, and Ions200
- Ch.3 - Chemical Reactions and Reaction Stoichiometry176
- Ch.4 - Reactions in Aqueous Solution155
- Ch.5 - Thermochemistry126
- Ch.6 - Electronic Structure of Atoms131
- Ch.7 - Periodic Properties of the Elements126
- Ch.8 - Basic Concepts of Chemical Bonding123
- Ch.9 - Molecular Geometry and Bonding Theories143
- Ch.10 - Gases147
- Ch.11 - Liquids and Intermolecular Forces91
- Ch.12 - Solids and Modern Materials122
- Ch.13 - Properties of Solutions126
- Ch.14 - Chemical Kinetics174
- Ch.15 - Chemical Equilibrium101
- Ch.16 - Acid-Base Equilibria139
- Ch.17 - Additional Aspects of Aqueous Equilibria146
- Ch.18 - Chemistry of the Environment72
- Ch.19 - Chemical Thermodynamics129
- Ch.20 - Electrochemistry142
- Ch.21 - Nuclear Chemistry101
- Ch.22 - Chemistry of the Nonmetals68
- Ch.23 - Transition Metals and Coordination Chemistry66
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry10
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Non è quello che usi tu?Cambia libro di testo
Capitolo 5, Problema 79
Gasoline is composed primarily of hydrocarbons, including many with eight carbon atoms, called octanes. One of the cleanest–burning octanes is a compound called 2,3,4- trimethylpentane, which has the following structural formula: The complete combustion of one mole of this compound to CO2(g) and H2O(g) leads to ΔH° = -5064.9 kJ. (b) By using the information in this problem and data in Table 5.3, calculate H°f for 2,3,4-trimethylpentane.
Guida verificata passo dopo passo1
Identify the balanced chemical equation for the complete combustion of 2,3,4-trimethylpentane: C_8H_{18} + \(\frac{25}{2}\)O_2 \(\rightarrow\) 8CO_2 + 9H_2O.
Use the standard enthalpy of formation (\(\Delta\) H_f^\(\circ\)) values from Table 5.3 for CO_2(g) and H_2O(g) to calculate the total \(\Delta\) H_f^\(\circ\) for the products.
Recall that the standard enthalpy change of the reaction (\(\Delta\) H_{rxn}^\(\circ\)) is given by: \(\Delta\) H_{rxn}^\(\circ\) = \(\sum\) \(\Delta\) H_f^\(\circ\) (products) - \(\sum\) \(\Delta\) H_f^\(\circ\) (reactants).
Substitute the known \(\Delta\) H_{rxn}^\(\circ\) value (-5064.9 kJ) and the calculated \(\Delta\) H_f^\(\circ\) for the products into the equation to solve for \(\Delta\) H_f^\(\circ\) of 2,3,4-trimethylpentane.
Rearrange the equation to isolate \(\Delta\) H_f^\(\circ\) for 2,3,4-trimethylpentane and solve for its value.
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Combustion Reactions
Combustion reactions involve the reaction of a substance with oxygen, producing heat and light. In organic chemistry, complete combustion of hydrocarbons results in carbon dioxide (CO2) and water (H2O) as products. Understanding the stoichiometry of these reactions is essential for calculating energy changes, such as enthalpy changes (ΔH), which indicate the heat released or absorbed during the reaction.
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02:24
Combustion Apparatus
Enthalpy of Formation (H°f)
The enthalpy of formation (H°f) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. It is a crucial concept in thermodynamics, allowing chemists to calculate the energy changes associated with chemical reactions. By using Hess's law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes for individual steps, one can derive the H°f for compounds from known enthalpy values.
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02:34Enthalpy of Formation
Hess's Law
Hess's Law states that the total enthalpy change for a chemical reaction is the same, regardless of the pathway taken, as long as the initial and final conditions are the same. This principle allows for the calculation of enthalpy changes by combining known enthalpy values from related reactions. In the context of the question, Hess's Law can be applied to determine the enthalpy of formation for 2,3,4-trimethylpentane by using the enthalpy change from its combustion and the enthalpies of formation of the products.
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02:03Hess's Law
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Using values from Appendix C, calculate the value of H for each of the following reactions: (a) NiO(s) + 2 HCl(g) → NiCl2(s) + H2O(g)
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Domanda del libro di testo
Ethanol (C2H5OH) is blended with gasoline as an automobile fuel. (c) Calculate the heat produced per liter of ethanol by combustion of ethanol under constant pressure. Ethanol has a density of 0.789 g/mL.
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Domanda del libro di testo
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Diethyl ether, C4H10O(l), a flammable compound that was once used as a surgical anesthetic, has the structure The complete combustion of 1 mol of C4H10O(l) to CO2(g) and H2O(l) yields ΔH° = -2723.7 kJ. (a) Write a balanced equation for the combustion of 1 mol of C4H10O(l).
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