AP Chemistry / Unit 9: Thermodynamics and Electrochemistry
9.2 Absolute Entropy and Entropy Change
Notes
$$\Delta S^\circ_{rxn}=\sum S^\circ(\text{products})-\sum S^\circ(\text{reactants})$$
- Standard entropies of elements are NOT zero.
Practice
$S^\circ$: A = 50, B = 120 J/(mol·K). For $A\to B$, $\Delta S^\circ=$
$120-50$.
The standard entropy of $O_2(g)$:
Only perfect crystals at 0 K have zero entropy.
A reaction with fewer moles of gas in the products probably has:
Less dispersal.
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