y.a.m160
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Hi, I’m revising over the energetics section for AQA & I’m just really confused as to what method to use to find things like enthalpy of formation & combustion.

I thought we could use the ‘products take away reactants’ method for enthalpy of formation & ‘reactants take away products’ for combustion, but we have a new teacher this year who told me it’s better to use the method where you draw out the arrows & stuff to find it but I get confused easily with those & he said not to use the equation method bc it’s easy to make a mistake with it...
is that true bc the method I’ve been using is nowhere in the revision books or guides so I’m worried if I actually do need to learn the diagram method instead even tho I struggle with it.

Thank you for any advice!! Xx
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Pigster
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If you get the right answer, it is the right method.

I used to teach it the way you can do it, but a long time ago, I found that using arrows tended to be easier for my students to understand (and apply correctly), so I swapped.
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JessNaomi19600
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I personally find it easier to use Hess cycles (with the arrows) as it helps me to visualise which direction the reaction is going in. However, if you find it easier using the formula and are getting the answers right, I don't see why it should be a problem. Just check with your exam board specification that you won't be requires to use or draw a Hess cycle in your exam. If you do have to, here are some resources to help you better understand it:

Hope this helps
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