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Topic: molar enthalpy  (Read 5261 times)

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Offline mandyj

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molar enthalpy
« on: July 08, 2008, 06:56:16 PM »
what is the molar enthalpy for iron (II) sulfide in this rxn?
4FeS(s) + 7O2(g) ---> 2 Fe2O3 (s) + 4 SO2 (g)    (delta) Hc = -2456 kJ


~is this question asking for the energy of one mole of iron (II) sulfide?
« Last Edit: July 08, 2008, 07:13:08 PM by mandyj »

Offline Dan

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Re: molar enthalpy
« Reply #1 on: July 09, 2008, 04:02:42 AM »
~is this question asking for the energy of one mole of iron (II) sulfide?

Probably. It looks like you've been given the enthalpy of combustion for 4 mol of FeS, so you have to work out the amount of heat released or consumed per mole of FeS.

It isn't a very well written question, and given the absence of any other data I don't see what else you could really be expected to calculate.
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Offline cliverlong

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Re: molar enthalpy
« Reply #2 on: July 09, 2008, 04:33:34 PM »
what is the molar enthalpy for iron (II) sulfide in this rxn?
4FeS(s) + 7O2(g) ---> 2 Fe2O3 (s) + 4 SO2 (g)    (delta) Hc = -2456 kJ


~is this question asking for the energy of one mole of iron (II) sulfide?
My book (CGP A2 Chemistry revision guide) defines Enthalpy change of formation DHf as

The enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions

So if molar enthalpy for iron (II) sulfide means Enthalpy change of formation of iron (II) sulfide then the relevant equation would be

Fe(s) + S(s) -> FeS(s)

Then you would be able to use the information you are given but you would need a lot more data and plug it into a relevant Born-Haber cycle to work out Enthalpy change of formation of iron (II) sulfide

However, if molar enthalpy for iron (II) sulfide means something different then I don't have any ideas.


Clive

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