## Standard enthalpies of formation

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### Standard enthalpies of formation

So I am confused on when calculating the change in enthalpy under standard conditions in order to find the change in Gibbs free energy. Say they asked calculate the change in enthalpy for the formation of CO. Would you use the chemical reaction: 2C + O2 --> 2CO or C + 1/2O2 --> CO. How do you know which one to use since they are both balanced correctly but give different answers. Thanks

Chem_Mod
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### Re: Standard enthalpies of formation

By definition, standard enthalpy of formation is per the formation of 1 mole of a compound.

Caity Colt 2N
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### Re: Standard enthalpies of formation

You can use either equation, but because the equation 2C + O2 --> 2CO is for two moles of CO, you would need to multiply the ∆H°by 2. Then you should end up getting the same answer.