Textbook Question
(a) In a chemical reaction, two gases combine to form a solid. What do you expect for the sign of ΔS?
Ch.19 - Chemical Thermodynamics
Chapter 19, Problem 34b
(b) How does the entropy of the system change in the processes described in Exercise 19.12?
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Identify the processes described in Exercise 19.12. These processes could involve changes in physical state, mixing of substances, or chemical reactions. Understanding the nature of these processes is crucial for analyzing entropy changes.
Recall the concept of entropy. Entropy is a measure of the disorder or randomness in a system. Generally, processes that increase disorder (such as melting, vaporization, or mixing) result in an increase in entropy, while processes that decrease disorder (such as freezing or condensation) result in a decrease in entropy.
For each process, determine whether the system becomes more ordered or more disordered. For example, if a solid melts into a liquid, the system becomes more disordered, indicating an increase in entropy.
Consider the molecular perspective: Analyze how the movement and arrangement of molecules change during each process. Increased molecular motion and dispersion typically lead to higher entropy.
Summarize the entropy changes for each process. State whether the entropy of the system increases, decreases, or remains unchanged based on the analysis of molecular disorder and the nature of the process.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Entropy
Entropy is a measure of the disorder or randomness in a system. In thermodynamics, it quantifies the number of microscopic configurations that correspond to a thermodynamic system's macroscopic state. A higher entropy indicates a greater degree of disorder, while a lower entropy suggests more order. Understanding how entropy changes during processes is crucial for predicting the spontaneity and direction of chemical reactions.
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Second Law of Thermodynamics
The Second Law of Thermodynamics states that the total entropy of an isolated system can never decrease over time. It implies that natural processes tend to move towards a state of maximum disorder or entropy. This law is fundamental in determining whether a process is spontaneous; if the entropy of the universe increases, the process is likely to occur. This principle is essential for analyzing changes in entropy during chemical reactions or physical transformations.
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Gibbs Free Energy
Gibbs Free Energy (G) is a thermodynamic potential that measures the maximum reversible work obtainable from a system at constant temperature and pressure. It combines the system's enthalpy and entropy to determine spontaneity; a negative change in Gibbs Free Energy (ΔG < 0) indicates a spontaneous process. Understanding Gibbs Free Energy is crucial for analyzing how entropy changes in various processes, as it directly relates to the balance between enthalpy and entropy.
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