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 36
Does the entropy of the system increase, decrease, or stay the same when (a) the temperature of the system increases, (b) the volume of a gas increases, and (c) equal volumes of ethanol and water are mixed to form a solution?
Verified step by step guidance1
Step 1: Understand the concept of entropy. Entropy is a measure of the disorder or randomness in a system. In general, processes that increase disorder increase entropy, while those that decrease disorder decrease entropy.
Step 2: Analyze scenario (a) - the temperature of the system increases. When temperature increases, the kinetic energy of the molecules increases, leading to greater molecular motion and disorder. Therefore, the entropy of the system is likely to increase.
Step 3: Analyze scenario (b) - the volume of a gas increases. When the volume of a gas increases, the gas molecules have more space to move around, which increases the disorder of the system. Thus, the entropy of the system is likely to increase.
Step 4: Analyze scenario (c) - equal volumes of ethanol and water are mixed to form a solution. Mixing two substances generally increases disorder because the molecules of each substance are distributed more randomly throughout the solution. Therefore, the entropy of the system is likely to increase.
Step 5: Summarize the findings. In all three scenarios, the entropy of the system increases due to increased disorder: (a) increased temperature leads to more molecular motion, (b) increased volume allows more space for gas molecules, and (c) mixing substances results in a more random distribution of molecules.
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. It quantifies the number of ways a system can be arranged, with higher entropy indicating greater disorder. In thermodynamics, processes that increase the number of accessible microstates typically lead to an increase in entropy, while processes that restrict arrangements lead to a decrease.
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Effect of Temperature on Entropy
Increasing the temperature of a system generally increases its entropy. This is because higher temperatures provide more energy to the particles, allowing them to move more freely and occupy a greater number of microstates. As a result, the overall disorder of the system increases, leading to higher entropy.
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Mixing of Substances
When two substances, such as ethanol and water, are mixed, the entropy of the resulting solution typically increases. This is due to the increased disorder that arises from the interaction and distribution of the molecules in the mixture. The mixing process allows for a greater number of possible arrangements of the molecules, thus enhancing the overall entropy of the system.
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Related Practice
Textbook Question
(b) How does the entropy of the system change in the processes described in Exercise 19.12?
Textbook Question
Indicate whether each statement is true or false. (a) Unlike enthalpy, where we can only ever know changes in H, we can know absolute values of S. (b) If you heat a gas such as CO2, you will increase its degrees of translational, rotational and vibrational motions. (c) CO2(g) and Ar(g) have nearly the same molar mass. At a given temperature, they will have the same number of microstates.