Question

Consider the following reaction, which is involved in the purification of iron from its ores. Some relevant thermodynamic data is shown below.

Fe2O3 (s) + 3CO(g) → 2Fe(s) + 3 CO2 (g) ΔS° = 15.2 J/K

Substance	∆Hf° (kJ/mol)	S° (J/K/mol)	∆Gf° (kJ/mol)
Fe2O3(s)	–824.2	87.40	??
CO(g)	–110.5	197.6	–137.2
Fe(s)	0	??	0
CO2(g)	–393.5	213.6	–394.4

a) Find ΔH° for the reaction above.

b) Find S° for solid iron.

c) Find ∆Gf° for Fe2O3.

*** I know the answers, I just need help on the steps. ***

Answer 1

a)

dH= Hprod - Hreact

dH = (2*0 + 3*-393.5) - (-824.2 + 3*-110.5)= -24.8 kJ

b)

dS = Sprod - Sreact

dS = 2*S-Fe + 3*S-CO2 - (S-Fe2O3 + 3*S-CO)

15.2 = 2*S-Fe + 3*213.6 - (87.4 + 3*197.6)

S-Fe = ((15.2) - (3*213.6 - (87.4 + 3*197.6) ))/2

S-Fe = 27.3 J/molK

c)

dG for Fe2O3

so

dG = dGprod - dGreact

dG = dH - T+dS = (-24800) - 298*(15.2) = -29329.6 J/mol = -29.32 kJ/mol

so

-29.32 = 2*0 + 3*-394.4 - (G-Fe2O3 + 3*-1372.)

-29.32 + 3*394.4 -3*(137.2) = dG-Fe2O3

dG - Fe2O3 = -742.28 kJ/mol