Standard enthalpies of formation

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Adam_Alyafaie_1L
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Joined: Wed Sep 21, 2016 2:58 pm

Standard enthalpies of formation

Postby Adam_Alyafaie_1L » Sun Jan 29, 2017 7:11 pm

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

Postby Chem_Mod » Sun Jan 29, 2017 9:23 pm

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

Postby Caity Colt 2N » Sun Jan 29, 2017 9:26 pm

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.

Tyler_Honrada_1L
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Re: Standard enthalpies of formation

Postby Tyler_Honrada_1L » Sun Feb 12, 2017 11:59 pm

Okay, wait... so the things that can change the change of heat of the reaction include using the reverse reaction, and multiplying to change the coefficient?


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