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Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium
Chapter 18, Problem 57b

Which state in each of the following pairs has the higher entropy per mole of substance? (b) N2 at STP or N2 at 0 °C and 10 atm

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Entropy is a measure of the disorder or randomness in a system. In general, gases have higher entropy than liquids, and liquids have higher entropy than solids.
For gases, entropy increases with an increase in volume or a decrease in pressure, as the molecules have more space to move around.
STP (Standard Temperature and Pressure) is defined as 0 °C and 1 atm.
Compare the two conditions: N_2 at STP (0 °C, 1 atm) and N_2 at 0 °C and 10 atm.
Since the temperature is the same in both cases, focus on the pressure: lower pressure (1 atm) at STP means higher volume and thus higher entropy compared to 10 atm.

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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. It quantifies the number of microscopic configurations that correspond to a thermodynamic system's macroscopic state. Higher entropy indicates greater disorder and more available microstates, which typically occurs in gases compared to liquids and solids.
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Ideal Gas Law

The Ideal Gas Law relates the pressure, volume, temperature, and number of moles of an ideal gas through the equation PV = nRT. This law helps predict how gases behave under different conditions, including changes in temperature and pressure, which directly affect the entropy of the gas.
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Standard Temperature and Pressure (STP)

Standard Temperature and Pressure (STP) is defined as a temperature of 0 °C (273.15 K) and a pressure of 1 atm. At STP, gases behave ideally, and their properties, including entropy, can be compared more easily. Deviations from STP, such as increased pressure or decreased temperature, can significantly alter a gas's entropy.
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