[Nick12]

For the reduction of Cr₂)O₃ by Al, Delta G is aprrox -350kJ/mol.

The question: This reaction is thermodynamically spontaneous at all temperatures.  Explain why mixtures of Cr₂O₃ and Al do not, however, spontaneously react at all temperatures.

This is a past exam question and Id like a model answer to help me understand it.

[Borek]

For the same reason papers on my desk don't burn at the moment (although they are very slowly oxidized).