2Fe 2 O 3 (s) + 3C (s) –––> 4Fe (s) + 3CO 2 (g) H (KJ/mol) S (J/molK) (A) Calcul

ID: 929555 • Letter: 2

Question

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

H (KJ/mol)

S (J/molK)

(A) Calculate G° for this reaction

(B) How many electrons are transferred in the balanced reaction above?

(D) Using the Nernst Equation,what is the E value of the reaction if the partial pressure of CO2 drops to 0.0346 atm?

(E) Explain in a complete sentence why this reaction is or is not spontaneous using both G and E found above

Reaction 2Fe2O3 (s) 3C (s) –––> 4Fe (s) 3CO2 (g)

H (KJ/mol)

-824.2 0 0 -397.5

S (J/molK)

87.4 5.74 27.23 213.6

G = dH- TdS

dH = (4*0-3*397.5)-(2*-824.2 + 3*0) = 455.9 kJ/mol

DS = 4*27.23+3*213.6 -2*87.4-3*5.74 = 557.7 J/molK

then

G = 455.9*1000 - 298*557.7 = 289705.4 J/mol K

Fe+3 --> Fe0

C0 --> C+4

n = 3*4 = 6 electrons

G = -nF*E°cell then

E°cell = G/(-nF) = 289705.4 /(-6*96500) = -0.500354

Ecell = E°cell - 0.0592/n*LogQ

Ecell = 0.500354- 0.0592/6*LogQ

Q = PCO2^3 = (0.0346^3) = 0.000041421 atm

Ecell = 0.500354- 0.0592/6*Log0.000041421 = 0.54359

This is not spontanous

since G < 0 and E < 0

for the addition of CO2 it will fhist equilibrium toward reactants, therefore it is not spontanous!

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