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Ch.19 - Chemical Thermodynamics
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
All textbooksBrown 14th EditionCh.19 - Chemical ThermodynamicsProblem 11e
Chapter 19, Problem 11e

Which of the following processes are spontaneous and which are nonspontaneous: (e) formation of CH4 and O2 molecules from CO2 and H2O at room temperature and 1 atm of pressure?

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Understand the concept of spontaneity: A spontaneous process is one that occurs without needing to be driven by an external force. It is often associated with a decrease in free energy (ΔG < 0).
Identify the chemical reaction: The formation of CH₄ and O₂ from CO₂ and H₂O can be represented as: CO₂ + 2H₂O → CH₄ + 2O₂.
Consider the thermodynamics: Determine if the reaction is exothermic or endothermic by considering the enthalpy change (ΔH). Formation of CH₄ and O₂ from CO₂ and H₂O is typically endothermic, requiring energy input.
Evaluate the entropy change (ΔS): Consider the change in disorder. The reaction involves breaking stable CO₂ and H₂O molecules to form CH₄ and O₂, which may decrease entropy.
Apply Gibbs Free Energy equation: Use ΔG = ΔH - TΔS to assess spontaneity. If ΔG is positive, the process is nonspontaneous under the given conditions (room temperature and 1 atm).

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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 spontaneous process is one that occurs without needing to be driven by an external force. In thermodynamics, spontaneity is often determined by the change in Gibbs free energy (ΔG); if ΔG is negative, the process is spontaneous. This concept is crucial for understanding whether a reaction will proceed under given conditions.
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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. The equation ΔG = ΔH - TΔS relates changes in enthalpy (ΔH) and entropy (ΔS) to spontaneity. A negative ΔG indicates that the reaction can occur spontaneously.
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Standard Conditions

Standard conditions refer to a set of specific conditions (usually 1 atm pressure and a specified temperature, often 25°C) under which thermodynamic data is tabulated. These conditions are essential for comparing the spontaneity of reactions, as they provide a consistent reference point for calculating Gibbs free energy and other thermodynamic properties.
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Related Practice
Textbook Question

Indicate whether each statement is true or false. (a) A reaction that is spontaneous in one direction will be nonspontaneous in the reverse direction under the same reaction conditions. (b) All spontaneous processes are fast. (c) Most spontaneous processes are reversible. (d) An isothermal process is one in which the system loses no heat. (e) The maximum amount of work can be accomplished by an irreversible process rather than a reversible one.

Textbook Question

Which of the following processes are spontaneous and which are nonspontaneous: (d) lightning

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Textbook Question

Which of the following processes are spontaneous?

a. the melting of ice cubes at −10 °C and 1 atm pressure

b. separating a mixture of N2 and O2 into two separate samples, one that is pure N2 and one that is pure O2

c. alignment of iron filings in a magnetic field

d. the reaction of hydrogen gas with oxygen gas to form water vapor at room temperature

e. the dissolution of HCl(g) in water to form concentrated hydrochloric acid

Textbook Question

Which of the following processes are spontaneous and which are nonspontaneous: (a) the ripening of a banana