Standard Entropy and Entropy Change of Reactions?

Using standard entropy values (from your text), calculate ΔS° for the following reactions.








a. C(s,diamond) -%26gt; C(s,graphite)





b. 2 CO(g) + 5 H2(g) -%26gt; C2H6(g) + 2 H2O(g)





c. 3 O2(g) -%26gt; 2 O3(g)

Standard Entropy and Entropy Change of Reactions?
The key to answering this question is the words "from your text". You need to look up the standard entropy values then use the equation:


ΔS° = Σ(S°,products) - Σ(S°,reactants)


making sure you allow for the correct number of moles of each substance.
Reply:a. This one is tough, however, entropy should be increasing. Why? Crystals(diamond) have ZERO randomness. Solids are very orderly, but still contain some randomness.





b. Entropy decreases, as there are more gas molecules on the reactant side.





c. Entropy decreases again because reactant has an additional molecule.

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