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Energetics Chemistry Question (Delta H)

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Hey guys, so it's something that's been bothering me quite alot lately :P

When solving Delta H questions, how do you know when to do DeltaH products - DeltaH reactants or DeltaH reactants - DeltaH products?

Thanks in advance! :)

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Okay, so this is a stupid rule, but I seem to remember it. 

 

For enthalpies of combustion, it is reactants minus products, which I remember as CRAP (Combustion Reactants minus Products) :P Then bond enthalpies are also reactants minus products, which I don't really have a rule for. 

 

Everything else (including delta G and delta S calculations) are products minus reactants. 

Edited by Sofia.
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Okay, so this is a stupid rule, but I seem to remember it. 

 

For enthalpies of combustion, it is reactants minus products, which I remember as CRAP (Combustion Reactants minus Products) :P Then bond enthalpies are also reactants minus products, which I don't really have a rule for. 

 

Everything else (including delta G and delta S calculations) are products minus reactants. 

Ahh okay great! Thank you Sofia! :D I'll remember it, especially the CRAP rule.. very handy and useful (Y) 

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