The value of ∆f G0 for Cr2O3 is -540 kJ/mole & that of Al2O3 is - 82

1.	The value of ∆f G0 for Cr2O3 is -540 kJ/mole & that of Al2O3 is - 827kJ/mole. Is the reduction of Cr2O3 possible with aluminium?
Answer» The desired conversion is 4Al + 2Cr₂O₃ → 2Al₂O₃ + 4Cr It is obtained by addition of following two reactions: 4Al + 3O₂ → 2 Al₂O₃ ∆_fG⁰ = -827 kJ/mole 2Cr₂O₃ → 4Cr + 3O₂ ∆_f G⁰ = + 540 kJ/mole Therefore, ∆ G⁰ for desired reaction is -827+ 540 = -287, as a result reduction is possible.

The value of ∆f G0 for Cr2O3 is -540 kJ/mole & that of Al2O3 is - 827kJ/mole. Is the reduction of Cr2O3 possible with aluminium?

Answer»

The desired conversion is

4Al + 2Cr₂O₃ → 2Al₂O₃ + 4Cr

It is obtained by addition of following two reactions:

4Al + 3O₂ → 2 Al₂O₃ ∆_fG⁰ = -827 kJ/mole

2Cr₂O₃ → 4Cr + 3O₂ ∆_f G⁰ = + 540 kJ/mole

Therefore, ∆ G⁰ for desired reaction is -827+ 540 = -287, as a result reduction is possible.