Textbook Question
Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ion batteries. (a) Calculate the mass percent lithium in each electrode material.
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Ch.20 - Electrochemistry
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970
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Table of contents
- 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: 9780137542970Not the one you use?Change textbook
Chapter 20, Problem 85a
(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?
Verified step by step guidance1
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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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
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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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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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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Related Practice
Textbook Question
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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Textbook Question
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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Textbook Question
(b) Can the “fuel” of a fuel cell be a solid?
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