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General Principles and Processes of Isolation of Elements
the reaction nbsp nbsp nbsp cr2o3 nbsp...

Question:
The reaction,

Cr₂O₃ + 2Al → Al₂O₃+ 2Cr (ΔG_o= -421kJ)

is thermodynamically feasible as is apparent from the Gibbs energy value. Why does it not take place at room temperature?

Answer:

The change in Gibbs energy is related to the equilibrium constant, K as

ΔG = - RT in K

At room temperature, all reactants and products of the given reaction are in the solid state. As a result, equilibrium does not exist between the reactants and the products. Hence, the reaction does not take place at room temperature. However, at a higher temperature, chromium melts and the reaction takes place.

We also know that according to the equation,

ΔG = ΔH - TΔS

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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Question:
The reaction,

Cr₂O₃ + 2Al → Al₂O₃+ 2Cr (ΔG_o= -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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Question: The reaction, Cr2O3 + 2Al → Al2O3 + 2Cr (ΔGo = -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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Question:
The reaction,

Cr₂O₃ + 2Al → Al₂O₃+ 2Cr (ΔG_o= -421kJ)

is thermodynamically feasible as is apparent from the Gibbs energy value. Why does it not take place at room temperature?