The reaction
`Cr_2O_3+2AltoAl_2O_3+2Cr` `(triangleG^(ɵ)=-421kJ))`
Is thermodynamically feasible as is apparent from the Gibbs energy value. Why does it not take place at room temperature?

Explanation

The interpretation of `Delta G^(@)` is based upon on K ` (DeltaG^(@) = - RT ` ln K ), the equilibrium constant. Since in the given redox reaction, all the reactants and the products are solids at room temperature, therefore, there does not exist any equilibrium between the reactants and the products and hence the reaction does not occur at room temperature. However, at high temperature, when chromium melts, the value of ` T Delta S ` increases. Aa a result , the value of ` Delta _rG^(@)` becomes more - ve and hence the reaction proceeds rapidly.