Domanda del libro di testo
(b) Can the “fuel” of a fuel cell be a solid?
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Ch.20 - Electrochemistry
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232
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TOC.tableOfContents
- Ch.1 - Introduction: Matter, Energy, and Measurement177
- Ch.2 - Atoms, Molecules, and Ions231
- Ch.3 - Chemical Reactions and Reaction Stoichiometry216
- Ch.4 - Reactions in Aqueous Solution189
- Ch.5 - Thermochemistry175
- Ch.6 - Electronic Structure of Atoms168
- Ch.7 - Periodic Properties of the Elements150
- Ch.8 - Basic Concepts of Chemical Bonding177
- Ch.9 - Molecular Geometry and Bonding Theories200
- Ch.10 - Gases179
- Ch.11 - Liquids and Intermolecular Forces113
- Ch.12 - Solids and Modern Materials154
- Ch.13 - Properties of Solutions157
- Ch.14 - Chemical Kinetics199
- Ch.15 - Chemical Equilibrium128
- Ch.16 - Acid-Base Equilibria164
- Ch.17 - Additional Aspects of Aqueous Equilibria163
- Ch.18 - Chemistry of the Environment105
- Ch.19 - Chemical Thermodynamics164
- Ch.20 - Electrochemistry171
- Ch.21 - Nuclear Chemistry122
- Ch.22 - Chemistry of the Nonmetals82
- Ch.23 - Transition Metals and Coordination Chemistry79
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry16
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Capitolo 20, Problema 81a
(a) Which reaction is spontaneous in the hydrogen fuel cell: hydrogen gas plus oxygen gas makes water, or water makes hydrogen gas plus oxygen gas?
Guida verificata passo dopo passo1
Identify the reactions involved in the hydrogen fuel cell. The two reactions to consider are: 1) Hydrogen gas (H2) reacting with oxygen gas (O2) to form water (H2O), and 2) Water (H2O) decomposing into hydrogen gas (H2) and oxygen gas (O2).
Understand the concept of spontaneity in chemical reactions. A spontaneous reaction is one that occurs naturally under certain conditions without the need for continuous external energy.
Consider the standard Gibbs free energy change (\(\Delta G^\circ\)) for each reaction. The sign of \(\Delta G^\circ\) helps determine spontaneity: if \(\Delta G^\circ < 0\), the reaction is spontaneous; if \(\Delta G^\circ > 0\), the reaction is non-spontaneous.
Recall the formation of water from hydrogen and oxygen (Reaction 1) is exothermic and releases energy, typically indicating a negative \(\Delta G^\circ\) and thus spontaneity under standard conditions.
Analyze the decomposition of water into hydrogen and oxygen (Reaction 2). This reaction requires an input of energy (endothermic), suggesting a positive \(\Delta G^\circ\) and thus it is non-spontaneous under standard conditions.
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Spontaneity of Reactions
A reaction is considered spontaneous if it occurs naturally under given conditions without external influence. This is often determined by the change in Gibbs free energy (ΔG); if ΔG is negative, the reaction is spontaneous. In the context of the hydrogen fuel cell, understanding spontaneity helps in identifying which direction of the reaction is favored energetically.
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04:20
Spontaneity of Processes
Gibbs Free Energy
Gibbs free energy is a thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure. It combines the system's enthalpy and entropy to predict the direction of chemical reactions. A negative ΔG indicates that the products of a reaction are favored, which is crucial for determining the spontaneity of the reactions in a hydrogen fuel cell.
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01:51Gibbs Free Energy of Reactions
Electrochemical Reactions
Electrochemical reactions involve the transfer of electrons between chemical species, which is fundamental in processes like those occurring in a hydrogen fuel cell. In these cells, hydrogen gas reacts with oxygen to produce water, releasing energy in the form of electricity. Understanding the nature of these reactions helps in analyzing which reaction direction is spontaneous and how energy is harnessed.
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02:46Electrochemical Cells
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Domanda del libro di testo
Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ion batteries. (b) Which material has a higher percentage of lithium? Does this help to explain why batteries made with LiMn2O4 cathodes deliver less power on discharging?
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Domanda del libro di testo
Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ion batteries. (c) In a battery that uses a LiCoO2 cathode, approximately 50% of the lithium migrates from the cathode to the anode on charging. In a battery that uses a LiMn2O4 cathode, what fraction of the lithium in LiMn2O4 would need to migrate out of the cathode to deliver the same amount of lithium to the graphite anode?
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