Hematite, Fe 2 O 3 (s), can be converted to pure iron, Fe(s), in many ways. The

ID: 696709 • Letter: H

Question

Hematite, Fe2O3(s), can be converted to pure iron, Fe(s), in many ways. The solid can be thermally decomposed:

(a) Fe2O3(s) 2 Fe(s) + 3/2 O2(g).

Or, it can be reacted with carbon, hydrogen, or aluminum:

(b) Fe2O3(s) + 3/2 C(s) 2 Fe(s) + 3/2 CO2(g)

(d) Fe2O3(s) + 2 Al(s) 2 Fe(s) + Al2O3(s)

At 1000 K, what is the standard Gibbs free energy for reaction (a)?

Select one:

a. +550 kJ mol-1

b. -86.6 kJ mol-1

c. -275 kJ mol-1

d. -913 kJ mol-1
Can you please show working :)

(a) Fe2O3(s) 2 Fe(s) + 3/2 O2(g).

H = H0fproducts – H0freactants

H = [(2x H0fFe(s) )+ ((3/2) x H0fO2 (g) )]- [ H0fFe2O3(s) ]

= [(2x(0))+((3/2)x(0))] - [-824.248] kJ/mol

= 824.248 kJ/mol

S = S0f products – S0f reactants

S = [(2x S0f Fe(s) )+ ((3/2) x S0f O2 (g) )]- [ S0fFe2O3(s) ]

= [(2x(27.28))+((3/2)x(205.03))] - [87.4] J/(mol-k)

= 274.7 J/(mol-k)

= 0.2747 kJ/(mol-K)

We know G = H - T S Where T = 1000K

= 824.248 - ( 1000 x 0.2747 ) kJ/mol

= +550 kJ/mol

Therefore option (a) is correct

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