Units for heat of reaction
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Units for heat of reaction
If you are given the heat of reaction in kJ but want to express it in terms of a reactant or product, is it correct to write "kJ per mole of said reactant or product?" Or is this an invalid statement?
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Re: Units for heat of reaction
I'm not sure exactly what you are asking for; however, kJ/mol is a perfectly valid unit.
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Re: Units for heat of reaction
If you want to do it in terms of product or reactant it would also be in terms of KJ/mole and that is called the heat of formation for the product or reactant.
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Re: Units for heat of reaction
I think that the unit should just be kJ/mol, because I think that adding or removing something from a unit would make things weird and even the unit invalid. If you want specify that you are calculating enthalpy of formation of a particular substance, you could specify that at the beginning of your equation, right after delta H rxn and before the = sign.
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Re: Units for heat of reaction
Yup! The standard enthalpy of formation for products and/or reactants should be in kJ/mol
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Re: Units for heat of reaction
805097738 wrote:do you have to explicitly state per mole or is that implied already
You should explicitly state it per mole in the case of standard reaction enthalpy or standard formation enthalpy because those are definitionally for one mole of a compound. I guess it's mostly for the consistency of units, though.
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Re: Units for heat of reaction
Yes, for the heat of reaction, you must state it in kj/mol because in a reaction, there could be 2 moles of a reactant being used to form a product, and in that case, the per mole part of the heat of reaction matters, because in that case you must divide the amount of heat by two. So yes, the per mole of reactant or product matters.
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Re: Units for heat of reaction
Also, if you keep track of units, it makes it easier to do any calculations you may need.
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Re: Units for heat of reaction
cancelling units when you solve the problem and keeping track of them is what I do to get the final units
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