Calculate Delta S, G, H

[FarMD2012]

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So I am a little confused about how to calculate Delta S, G, and H for a reaction.
I know its usually Product - Reactant, but some of them depends on how many moles there are and some don't.

For example, for Delta S, (2)O3 ---> (3)O2,
it is suppose to be 3 x O2(S) - 2 x O3(S), but for delta H, you don't have to multiply by 2 or 3? Please enlighten me, this is still one of the confusing topics to me, thank you!

 

[Rabolisk]

If you are given enthalpy or free energy of formation, then you have to multiply by the number of moles. Enthalpy of formation is the change in enthalpy when you form one mole of a substance from its elements in standard state.

 

[FarMD2012]

So let me get this straight, it will always be number of moles multiply by (S, G, or H) of formation for each gas or aqueous molecule of the product minus reactant?

 

[SoonerLuke]

So let me get this straight, it will always be number of moles multiply by (S, G, or H) of formation for each gas or aqueous molecule of the product minus reactant?

Yes that's correct. I think the thing that may be confusing you is that you DO NOT pay attention to the number of moles when calculating EMF with the voltaic cell, because they do not matter in that case. It took me awhile to get the two things straight in my head as well.

 

[FarMD2012]

YES! That's it, you have made me realize the difference, that is exactly what I was confused on, thank you!

 

[SoonerLuke]

Happy to be able to help. Happens to the best of us