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Cr(2)O(3)+2Al rarr Al(2)O(3)+2Cr, (Delta...

`Cr_(2)O_(3)+2Al rarr Al_(2)O_(3)+2Cr, (DeltaG^(@)=-"421 kJ")` is a thermodynamically feasible reaction as is apparent from the Gibbs energy value. Why does it not take place at room temperature?

Text Solution

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The interpretation of thermodynamic feasibility of a reaction `(DeltaG^(@))` is based on the equilibrium constant, K `(because DeltaG^(@)=-RT ln K)`. In the given redox reaction, the reactants and the products are solids at room temperature and hence, equilibrium does not exist between them. Therefore, the given reaction does not occur at room temperature.
However, at higher temperature, as chromium melts, the value of `TDeltaS` increases. Consequently `DeltaG^(@)` becomes more `-ve` and hence the reaction proceeds fast.
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