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Home » The value of ∆fG0 for formation of Cr2 O3 is – 540 kJmol−1 and that of Al2 O3 is – 827 kJmol−1 Is the reduction of Cr2 O3 possible with Al ?
The value of ∆fG0 for formation of Cr2 O3 is – 540 kJmol−1 and that of Al2 O3 is – 827 kJmol−1 Is the reduction of Cr2 O3 possible with Al ?
CBSE | Chemistry | Class 12 | General Principles and Processes of Isolation of Elements | NCERT
The value of ∆fG0 for formation of Cr2 O3 is – 540 kJmol−1 and that of Al2 O3 is – 827 kJmol−1 Is the reduction of Cr2 O3 possible with Al ?

Cr2O3 has a higher value of formation ( −540 kJ mol−1 ) than Al2O3 ( −827 kJ /mol ).

Therefore, Al can reduce Cr2O3 to Cr.

2Al + (3/2)O2 ⇒ Al2O3

2Cr + (3/2)O2 ⇒ Cr2O3

Subtracting,

2Al + Cr2O3⇒ Al2O3 +2Cr; ∆fGθ = -827 – ( -540 ) = -287kJ / mol

Since ∆fGθ is negative for the reduction reaction of Cr2O3 by Al , the reaction can take place.

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