Exergonic/Endergonic predictions via chemical equations

[The Peon]

In terms of entropy, if a chemical reaction is endergonic, will the reactants always have more total molecules than the products? And if exergonic, will it be the opposite, and the reactants will have more total molecules than the products?

Ex:

2C4H10 + 13O2 ---> 8CO2 + 10H2O

 

Reactants: 15 total molecules

 

Products: 18 total molecules

 

Reaction is exergonic, because the product has more total molecules than the reactants.

 

 

 

Ex 2:

CuSO₄ + 2NaOH ---> Cu(OH)₂ + Na₂SO₄

 

_{Reactants: 3 total molecules}

 

_{Products: 2 total molecules}

 

_{Reaction is endergonic, because the product has less total molecules than the reactants.}

[Sensei]

In terms of entropy, if a chemical reaction is endergonic, will the reactants always have more total molecules than the products?

 

 

Example against your theory:

 

2H₂ + O₂ -> 2H₂O

 

Reactants: 3 total molecules

 

Products: 2 total molecules

 

Reaction is exothermic.

Other example:

 

2 C₂H₂ + 5 O₂ -> 4 CO₂ + 2 H₂O

Edited February 15, 2014 by Sensei

[studiot]

Remember that the terms exothermic and endothermic refer to heat energy only, and does not include entropy effects directly.

 

There are more general energy balances, Chemists tend prefer the Gibbs Free Energy, which does include entropy in the TdS term.

Edited February 15, 2014 by studiot

[studiot]

Here is areference that may assist

 

http://en.wikipedia.org/wiki/Exergonic_reaction

[The Peon]

Thank you for the replies!