6.3 The reaction, Cr2O3+2Al → Al2O3+2Cr (?rG0 = – 421kJ) is thermodynamically feasible as is apparent from the Gibbs energy value. Why does it not take place at room temperature?
6.3 The reaction, Cr2O3+2Al → Al2O3+2Cr (?rG0 = – 421kJ) is thermodynamically feasible as is apparent from the Gibbs energy value. Why does it not take place at room temperature?
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1 Answer
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The reaction,
Cr2O3 + 2 Al → Al2 O3 + 2 Cr (ΔG0 = – 421 kJ)
Is thermodynamically feasible as is apparent from Gibbs energy value. The change in Gibbs free energy is
related to the equilibrium constant, k as
ΔG = - RT ln K
A certain amount of energy activation is required even for such reactions which are thermodynamically feasible, therefore heating is required.
ΔG = ΔH + S
Increasing the temperature increases the value of TΔS, making the value of ΔG more and more negative.
Therefore, the reaction becomes more and more feasible as the temperature is increased.
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