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Offline sandiegofan328

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Thermochem question...
« on: September 30, 2018, 07:51:44 PM »
Hello all,
I'm having quite a bit of trouble finding the answer to this Thermochemistry question, it is not located in either our textbook or lecture...I apologize for not showing my beginning work as I just lack direction on where to begin. I appreciate all attempts or hints to get me started. :)

4 Fe(s) + 3 O2(g)  2 Fe2O3(s)      ΔH = -1652 kJ
How much heat is released when 12.8 g Fe and 1.66 g O2 are reacted?

Would I convert to moles, multiply by the coefficient, and then multiply by delta H?
Thank you much

Offline sjb

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Re: Thermochem question...
« Reply #1 on: October 01, 2018, 02:27:29 AM »
Check your units, but almost there

Offline Borek

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Re: Thermochem question...
« Reply #2 on: October 01, 2018, 02:43:21 AM »
Deciding what is the limiting reagent won't hurt, but yes, as sjb suggested, you are on the right track.
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Offline aSad

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Re: Thermochem question...
« Reply #3 on: October 01, 2018, 03:54:24 PM »
hi, this is my first message on this forum...
is the given enthalpy for 1 mol of product?
if it is so, you should find the limiting reactant and with it, find the amount of Fe2O3.
then, multiply the mol number with the enthalpy, the result is the heat released...

Offline Borek

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Re: Thermochem question...
« Reply #4 on: October 01, 2018, 04:05:48 PM »
is the given enthalpy for 1 mol of product?

If it is not listed as per mole in most cases it is meant for a "reaction as written", so my bet would be 2 moles.
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Offline Enthalpy

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Re: Thermochem question...
« Reply #5 on: October 01, 2018, 06:37:07 PM »
Yes, 2 moles of Fe2O3. The Hdbk of Chem & Phys gives -824.2kJ/mol.

Offline sandiegofan328

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Re: Thermochem question...
« Reply #6 on: October 02, 2018, 09:09:22 AM »
Thanks for your help everyone, I plugged it in as 1 mole per the delta H and it worked.

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