Hess' law cycles-Standard enthalpy changes Watch

TheonlyMrsHolmes
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I am going over Hess' law cycles and I can't seem to remember why standard enthalpy change of formation always needs 1 mole of product on the right hand side and why combustion always has 1 mole of elements and compounds on the left side of the equation.

All I know is that it does! But whyyy?

Thanks
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Pigster
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To do it in a standard way.
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ETRC
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Formation is forming products- chemists need a way to calculate enthalpy change keeping most things constant so they calculate for 1 mol of products formed.

Combustion is reacting 1 mol of o2 and reactants.

Basically its all to do it in a standard way.
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Pigster
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(Original post by ETRC)
Formation is forming products- chemists need a way to calculate enthalpy change keeping most things constant so they calculate for 1 mol of products formed.

Combustion is reacting 1 mol of o2 and reactants.

Basically its all to do it in a standard way.
It is 1 mol of substance with as many mol of O2 as required for complete combustion.
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Parallex
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By definition - "The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy from the formation of 1 mole of the compound from its constituent elements, with all substances in their standard states at 1 atmosphere."
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ETRC
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(Original post by Pigster)
It is 1 mol of substance with as many mol of O2 as required for complete combustion.
oh yeah i worded it wrong, i was typing quickly
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