January 16, 2025, 12:18:31 PM
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Topic: determine the temperature at which carbon can reduce iron (III) oxide to iron  (Read 4995 times)

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Offline NewtoAtoms

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2Fe2O3 (g)  +  3C (s) ----------> 4 Fe (s)  +  3 CO2 (g)

I am assuming that this is an enthalpy question, therefore I would calculate it according to:

   ΔHorxn= [4(0 kJ/mol) + 3(-393.5 kJ/mol)] – [2(-824.2 kJ/mol) + 3(0 kJ/mol)] =
   ΔHorxn= [-1180.5 kJ/mol] – [-1648.4] = 467.9 kJ/mol

This means that 2 moles of Fe2O3 and 3 moles of C will need to 467.9 kJ/mol of heat added to be reduced to iron.
However I am confused because this is not answering the question : Determine the temperature at which carbon can reduce iron (III) oxide to iron.

Can anyone help direct me on the right path?
I would be so grateful for anyone's help.

Thank you so much

NewtoAtoms

Offline Astrokel

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What were you given? Enthalpies only? What about heat capacities?
No matters what results are waiting for us, it's nothing but the DESTINY!!!!!!!!!!!!

Offline NewtoAtoms

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I wasn't give any more information than the question itself, therefore I was stuck. 
Heat capacities are in the same chapter as enthalpies and I don't know which one is the one to use here?

I know that enthalpies show whether a reaction is endothermic or exothermic and that heat capacities is the amount of heat required to raise the temperature of a given quantity of a substance by one degree C. 

I thought when asking to determine the temperature "at which carbon can reduce iron (III) oxide to iron, it referred soley to enthalpy. 

Can you explain why you might suggest heat capacities???

Thank you for your time.

Offline Astrokel

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Quote
Can you explain why you might suggest heat capacities???
If you assume it is a closed system,  :delta: q = - :delta: w. You could relate it to temperature if you have values for molar heat capacities.
No matters what results are waiting for us, it's nothing but the DESTINY!!!!!!!!!!!!

Offline shanmac

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I also am working on this question and am wondering if I have done it properly... could someone let me know if I am on the right track?  Here is my leg work:

ΔH of CO2 (g) = -393.5 kJ/mol ∴ 3 mol CO2 (g) = -1180.5 kJ/mol
ΔH  of Fe (s) = 0 kJ/mol ∴ 4 mol Fe (s) = 0 kJ/mol
ΔH  of Fe2O3 (s) = -822.2 kJ/mol ∴  2 mol Fe2O3 (s) = -1644.4 kJ/mol
ΔH  of C (s) = 0 kJ/mol ∴ 3 mol C (s) = 0 kJ/mol
ΔH°rxn= ∑nΔHf(products) - ∑nΔHf(reactants)

ΔH°rxn= (-1180.5) + 0 - (-1644.4) + 0 = 463.9 kJ/mol

S° of CO2 (g) = 213.6 J/K•mol ∴ 3 mol CO2 (g) = 640.8 J/K•mol
S°  of Fe (s) = 27.2 J/K•mol ∴ 4 mol Fe (s) = 108.8 J/K•mol
S°  of Fe2O3 (s) = 90.0 J/K•mol ∴  2 mol Fe2O3 (s) = 180.0 J/K•mol
S°  of C (s) = 5.69 J/K•mol ∴ 3 mol C (s) = 17.07 J/K•mol
S°rxn= ∑S°(products) - ∑S°(reactants)

S°rxn= 552.53 J/K•mol = 0.5525 kJ/mol

T = ΔH
      ΔS

T = 463.9 kJ/mol ÷ 0.5525 kJ/mol = 839.6 K

Am I on the right track?  Thanks in advance...

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