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Ch.18 - Free Energy and Thermodynamics
Tro - Chemistry: A Molecular Approach 4th Edition
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Tutti i libri di testoTro 4th EditionCh.18 - Free Energy and ThermodynamicsProblema 58
Capitolo 18, Problema 58

What is ΔS° for the reaction between nitrogen gas and fluorine gas to form nitrogen trifluoride gas, and how can the sign of ΔS° be rationalized?

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Identify the balanced chemical equation for the reaction: \( N_2(g) + 3F_2(g) \rightarrow 2NF_3(g) \).
Determine the standard molar entropy (S°) values for each substance involved in the reaction from a reliable data source.
Calculate the change in standard entropy (ΔS°) for the reaction using the formula: \( \Delta S^\circ = \sum S^\circ_{\text{products}} - \sum S^\circ_{\text{reactants}} \).
Substitute the standard molar entropy values into the formula to find ΔS°.
Rationalize the sign of ΔS° by considering the change in the number of gas molecules: the reaction goes from 4 moles of gas (1 mole of \(N_2\) and 3 moles of \(F_2\)) to 2 moles of \(NF_3\), indicating a decrease in entropy.>

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Entropy (ΔS)

Entropy, denoted as ΔS, is a measure of the disorder or randomness in a system. In chemical reactions, it reflects the number of ways the particles can be arranged. A positive ΔS indicates an increase in disorder, while a negative ΔS suggests a decrease in disorder. Understanding how the states of reactants and products influence entropy is crucial for predicting the sign of ΔS in a reaction.
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Entropy in Thermodynamics

Gaseous State and Molar Volume

The gaseous state of matter has a higher degree of freedom and disorder compared to solids and liquids. When gases react, the change in the number of moles of gas can significantly affect the overall entropy. In the reaction between nitrogen gas and fluorine gas to form nitrogen trifluoride gas, the change in the number of gas molecules must be considered to determine the sign of ΔS.
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Standard Molar Volume

Reaction Stoichiometry

Reaction stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. For the given reaction, analyzing the stoichiometry helps in understanding how the number of moles of reactants and products changes. This change is essential for rationalizing the sign of ΔS, as it directly influences the overall disorder of the system.
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Stoichiometry Concept
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