Textbook Question
Which of these processes are nonspontaneous? Are the nonspontaneous processes impossible? a. a bike going up a hill b. a meteor falling to Earth c. obtaining hydrogen gas from liquid water d. a ball rolling down a hill
Ch.19 - Free Energy & Thermodynamics
Tro5th EditionChemistry: A Molecular ApproachISBN: 9780134874371
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Table of contents
- Ch.1 - Matter, Measurement & Problem Solving117
- Ch.2 - Atoms & Elements106
- Ch.3 - Molecules and Compounds128
- Ch.4 - Chemical Reactions and Chemical Quantities56
- Ch.5 - Introduction to Solutions and Aqueous Solutions84
- Ch.6 - Gases112
- Ch.7 - Thermochemistry96
- Ch.8 - The Quantum-Mechanical Model of the Atom60
- Ch.9 - Periodic Properties of the Elements86
- Ch.10 - Chemical Bonding I: The Lewis Model91
- Ch.11 - Chemical Bonding II: Molecular Shapes, VSEPR & MO Theory85
- Ch.12 - Liquids, Solids & Intermolecular Forces51
- Ch.13 - Solids & Modern Materials48
- Ch.14 - Solutions93
- Ch.15 - Chemical Kinetics114
- Ch.16 - Chemical Equilibrium68
- Ch.17 - Acids and Bases137
- Ch.18 - Aqueous Ionic Equilibrium154
- Ch.19 - Free Energy & Thermodynamics91
- Ch.20 - Electrochemistry105
- Ch.21 - Radioactivity & Nuclear Chemistry74
- Ch.22 - Organic Chemistry141
Chapter 19, Problem 31
Calculate the change in entropy that occurs in the system when 1.00 mole of isopropyl alcohol (C3H8O) melts at its melting point (-89.5 °C). See Table 12.9 for heats of fusion.
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Identify the formula for calculating the change in entropy (\( \Delta S \)) during a phase change: \( \Delta S = \frac{q_{\text{rev}}}{T} \), where \( q_{\text{rev}} \) is the heat absorbed or released during the process and \( T \) is the temperature in Kelvin.
Determine the heat of fusion (\( \Delta H_{\text{fus}} \)) for isopropyl alcohol from Table 12.9. This value represents the amount of heat required to melt one mole of isopropyl alcohol at its melting point.
Convert the melting point from Celsius to Kelvin by adding 273.15 to the Celsius temperature: \( T = -89.5 + 273.15 \).
Substitute the values into the entropy change formula: \( \Delta S = \frac{\Delta H_{\text{fus}}}{T} \). Ensure that \( \Delta H_{\text{fus}} \) is in the same units as the temperature (usually Joules and Kelvin).
Calculate the change in entropy (\( \Delta S \)) using the values obtained in the previous steps.
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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 amount of energy in a physical system that is not available to do work. When a substance changes state, such as melting, the entropy typically increases because the molecules move from a more ordered solid state to a less ordered liquid state.
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Heats of Fusion
The heat of fusion is the amount of energy required to change a substance from solid to liquid at its melting point without changing its temperature. This value is crucial for calculating the change in entropy during phase transitions, as it provides the necessary energy input to overcome intermolecular forces in the solid state.
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Phase Change Calculations
Phase change calculations involve determining the energy changes associated with transitions between solid, liquid, and gas states. For melting, the change in entropy can be calculated using the formula ΔS = ΔH_fusion / T, where ΔH_fusion is the heat of fusion and T is the absolute temperature in Kelvin. This relationship is essential for understanding how energy and disorder change during phase transitions.
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Related Practice
Textbook Question
Without doing any calculations, determine the sign of ΔSsys for each chemical reaction. a. 2 KClO3(s) → 2 KCl(s) + 3 O2(g) c. Na(s) + 2 Cl2(g) → NaCl(s) d. N2(g) + 3 H2(g) → 2 NH3(g)
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Textbook Question
Two systems, each composed of two particles represented by circles, have 20 J of total energy. Which system, A or B, has the greater entropy? Why?
Textbook Question
Calculate the change in entropy that occurs in the system when 1.00 mole of diethyl ether (C4H10O) condenses from a gas to a liquid at its normal boiling point (34.6 °C). See Table 11.7 for heats of vaporization.
Textbook Question
Without doing any calculations, determine the sign of ΔSsys for each chemical reaction. b. CH2=CH2( g) + H2( g) → CH3CH3( g)
Textbook Question
Two systems, each composed of three particles represented by circles, have 30 J of total energy. How many energetically equivalent ways can you distribute the particles in each system? Which system has greater entropy?