1. Iron metal is produced commercially by reducing iron(iI) oxide in iron ore wi

Question

1. Iron metal is produced commercially by reducing iron(iI) oxide in iron ore with carbon monoxide: Fe2Ods) + 3 CO(g) 2 Fe(s) + 3 CO2(g) "(a) (i) Calculate the standard enthalpy change for this reaction at 25°C. Answer: *(ii) Calculate the standard entropy change for this reaction at 25 °C. Answer: (ii) Calculate the standard free energy change for this reaction at 25 °c. Write down the equation that shows the relationship between free energy, enthalpy and entropy. Hint: Use the information found in (i) and (ii) to calculate free energy. Answer: (b) Is the reaction spontaneous under standard-state conditions at 25 °C? Hint: Is the sign for Go positive or negative? Answer: (c) Does the reverse reaction become spontaneous at higher temperatures? Explain. Answer:

Explanation / Answer

Q1

a)

dH = Hproducts - reactants

dH = (2Fe + 3CO2) - (Fe2O3 + 3CO)

dH = (2*0 + 3*-393.2) -(-824.2 + 3*-110.5)

dH = -23.9 kJ/mol

ii)

dS = sproducts - sreactatns

dS =  (2Fe + 3CO2) - (Fe2O3 + 3CO)

dS =  (2*27.3 + 3*213.8) - (87.4+ 3*197.7)

dS = 15.5 J/molK

iii

GRxn = Gprod - Greact

dG = (2Fe + 3CO2) - (Fe2O3 + 3CO)

dG = 2*0 + 3*(-394.4) - ( -742.2 +3*(-137.2))

dG = -29.4 kJ/mol

It can also be clacualted via

dG = dH - T*dS

dG = -23.9 - 298 * 15.5 /1000 = -28.519kJ/mol ( approx)

b)

since dg is negative

this must be spontaneous

c)

if reverse reaction:

dH = positive, dS = negative

then, this will NEVER be spotnaneous

dG = dH - T*dS = positive - T*negative = + + +

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