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Ch.19 - Chemical Thermodynamics
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Brown 14th EditionCh.19 - Chemical Thermodynamics문제 112a
19장, 문제 112a

When most elastomeric polymers (e.g., a rubber band) are stretched, the molecules become more ordered, as illustrated here:
Suppose you stretch a rubber band. (a) Do you expect the entropy of the system to increase or decrease?

검증된 단계별 안내
1
Understand the concept of entropy, which is a measure of the disorder or randomness in a system.
Recognize that when the rubber band is unstretched, the polymer molecules are in a tangled, disordered state.
Consider that stretching the rubber band aligns the polymer molecules, making them more ordered compared to their initial state.
Recall that an increase in order corresponds to a decrease in entropy according to the second law of thermodynamics.
Conclude whether the entropy of the rubber band increases or decreases based on the change in molecular order when stretched.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Entropy

Entropy is a measure of the disorder or randomness in a system. In thermodynamics, it quantifies the number of possible arrangements of particles in a system. A higher entropy indicates a more disordered state, while lower entropy suggests a more ordered state. Understanding how entropy changes during physical processes is crucial for predicting the behavior of materials, such as elastomers.
추천 영상:
가이드 코스
02:46
Entropy in Thermodynamics

Molecular Order in Polymers

Polymers, like rubber, consist of long chains of repeating units. When stretched, the molecular chains align more closely, leading to increased order within the material. This alignment reduces the freedom of movement of the polymer chains, which can affect the overall entropy of the system. Recognizing how stretching influences molecular arrangement is key to understanding the thermodynamic properties of elastomers.
추천 영상:
가이드 코스
01:29
Bond Order Calculation

Thermodynamic Principles

Thermodynamic principles govern the behavior of energy and matter in systems. The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time. When analyzing the stretching of a rubber band, it is essential to consider how energy input (stretching) affects the system's entropy and whether the overall process leads to an increase or decrease in entropy.
추천 영상:
가이드 코스
01:18
First Law of Thermodynamics
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교과서 질문

The reaction SO2(g) + 2 H2S(g) ⇌ 3 S(s) + 2 H2O(g) is the basis of a suggested method for removal of SO2 from power-plant stack gases. The standard free energy of each substance is given in Appendix C. (b) In principle, is this reaction a feasible method of removing SO2?

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교과서 질문

The reaction SO2(g) + 2 H2S(g) ⇌ 3 S(s) + 2 H2O(g) is the basis of a suggested method for removal of SO2 from power-plant stack gases. The standard free energy of each substance is given in Appendix C. (a) What is the equilibrium constant for the reaction at 298 K? (c) If PSO2 = PH2S and the vapor pressure of water is 25 torr, calculate the equilibrium SO2 pressure in the system at 298 K.

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교과서 질문

The reaction SO2(g) + 2 H2S(g) ⇌ 3 S(s) + 2 H2O(g) is the basis of a suggested method for removal of SO2 from power-plant stack gases. The standard free energy of each substance is given in Appendix C. (d) Would you expect the process to be more or less effective at higher temperatures?

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교과서 질문
Hydrogen gas has the potential for use as a clean fuel in reaction with oxygen. The relevant reaction is 2 H21g2 + O21g2 ¡ 2 H2O1l2 Consider two possible ways of utilizing this reaction as an electrical energy source: (i) Hydrogen and oxygen gases are combusted and used to drive a generator, much as coal is currently used in the electric power industry; (ii) hydrogen and oxygen gases are used to generate electricity directly by using fuel cells that operate at 85 °C. (a) Use data in Appendix C to calculate ∆H° and ∆S° for the reaction. We will assume that these values do not change appreciably with temperature.
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