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Ch.19 - Chemical Thermodynamics
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 15th EditionCh.19 - Chemical ThermodynamicsProblema 39
Capitolo 19, Problema 39

For each of the following pairs, predict which substance has the higher entropy per mole at a given temperature: (a) Ar(l) or Ar(g) (b) He(g) at 3 atm pressure or He(g) at 1.5 atm pressure (c) 1 mol of Ne(g) in 15.0 L or 1 mol of Ne(g) in 1.50 L (d) CO2(g) or CO2(s)

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Step 1: Understand the concept of entropy. Entropy is a measure of the disorder or randomness in a system. Generally, the more disordered a system is, the higher its entropy.
Step 2: Analyze part (a). Compare Ar(l) and Ar(g). Gases have higher entropy than liquids because gas molecules are more disordered and have more freedom of movement.
Step 3: Analyze part (b). Compare He(g) at 3 atm and He(g) at 1.5 atm. At lower pressure, gas molecules have more space to move around, leading to higher entropy.
Step 4: Analyze part (c). Compare 1 mol of Ne(g) in 15.0 L and 1 mol of Ne(g) in 1.50 L. A larger volume allows gas molecules more space to move, increasing entropy.
Step 5: Analyze part (d). Compare CO2(g) and CO2(s). Gases have higher entropy than solids because gas molecules are more disordered and have more freedom of movement.

Concetti chiave

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Entropy

Entropy is a measure of the disorder or randomness in a system. It quantifies the number of possible microstates that correspond to a given macrostate, with higher entropy indicating greater disorder. In general, gases have higher entropy than liquids or solids due to their increased freedom of movement and greater number of accessible microstates.
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Effect of Pressure on Gas Entropy

The entropy of a gas is influenced by its pressure. At higher pressures, gas molecules are compressed, leading to fewer available microstates and thus lower entropy. Conversely, at lower pressures, gas molecules have more space to move, resulting in higher entropy. This concept is crucial when comparing gases at different pressures.
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Entropy and Physical Changes

Volume and Entropy in Gases

The volume occupied by a gas also affects its entropy. A larger volume allows gas molecules to occupy more positions and states, increasing the system's entropy. Therefore, when comparing the same amount of gas in different volumes, the gas in the larger volume will have higher entropy due to the greater number of accessible microstates.
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