Textbook Question
Rank each set of substances in order of increasing standard molar entropy (S°). Explain your reasoning. a. NH3(g); Ne(g); SO2(g); CH3CH2OH(g); He(g) c. CH4(g); CF4(g); CCl4(g)
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Ch.18 - Free Energy and Thermodynamics
Chapter 18, Problem 5
What is the molar entropy of a pure crystal at 0 K, and what is the significance of the answer?
Verified step by step guidance1
Identify the concept: The problem is related to the Third Law of Thermodynamics.
Understand the Third Law of Thermodynamics: It states that the entropy of a perfect crystal at absolute zero temperature (0 K) is exactly zero.
Recognize the significance: At 0 K, a perfect crystal is in a state of perfect order, meaning there is only one possible microstate.
Explain the implication: Since entropy is a measure of disorder or the number of microstates, having only one microstate means the entropy is zero.
Conclude the significance: This concept helps in calculating absolute entropies of substances at temperatures above 0 K by providing a reference point.
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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Open Question
A reaction has ΔH°rxn = -112 kJ and ΔS°rxn = 354 J/K. At what temperature is the change in entropy for the reaction equal to the change in entropy for the surroundings?
Textbook Question
Which of these processes is spontaneous? a. the combustion of natural gas b. the extraction of iron metal from iron ore c. a hot drink cooling to room temperature d. drawing heat energy from the ocean's surface to power a ship
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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
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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?
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