In each of the following pairs, which compound would you expect to have the higher standard molar entropy: (a) C2H2(g) or C2H6(g)? (b) CO2(g) or CO(g)?

Name: Chemistry: The Central Science
Author: Brown
ISBN: 9780134414232

검증된 단계별 안내

Step 1: Understand that standard molar entropy (S°) is a measure of the amount of disorder or randomness in a system. Generally, more complex molecules and those with more atoms have higher entropy.

Step 2: For part (a), compare C2H2(g) and C2H6(g). Consider the molecular structure and the number of atoms in each compound. C2H6(g) has more atoms and is more complex than C2H2(g), which suggests it might have higher entropy.

Step 3: For part (b), compare CO2(g) and CO(g). Look at the molecular structure and the number of atoms. CO2(g) has more atoms than CO(g), which typically leads to higher entropy due to increased complexity and more possible microstates.

Step 4: Consider the phase of the compounds. Both pairs are in the gaseous state, so phase does not affect the comparison in this case.

Step 5: Conclude that in both comparisons, the compound with more atoms and greater molecular complexity is expected to have the higher standard molar entropy.

주요 개념

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Standard Molar Entropy

Standard molar entropy is a measure of the amount of disorder or randomness in a system at standard conditions (1 bar, 25°C). It reflects the number of accessible microstates for a given amount of substance. Generally, larger and more complex molecules have higher entropies due to increased molecular motion and greater vibrational modes.

Molecular Complexity

Molecular complexity refers to the size and structure of a molecule, including the number of atoms and the types of bonds present. More complex molecules, such as those with more carbon and hydrogen atoms, typically have higher entropies because they can adopt more configurations and have more ways to distribute energy among their atoms.

Phase of Matter

The phase of matter significantly influences entropy, with gases generally having higher entropies than liquids and solids. This is due to the greater freedom of movement and higher kinetic energy of gas molecules, which allows for a larger number of microstates compared to more ordered phases.