Class 12 Chemistry - Chapter General Principles and Processes of Isolation of Elements NCERT Solutions | The reaction, Cr
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?
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.
More Questions From Class 12 Chemistry - Chapter General Principles and Processes of Isolation of Elements
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Outline the principles of refining of metals by the following methods:
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Popular Questions of Class 12 Chemistry
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For the reaction R → P, the concentration of a reactant changes from 0.03 M to 0.02 M in 25 minutes. Calculate the average rate of reaction using units of time both in minutes and seconds.
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(iii) Tris(ethane-1,2-diamine) chromium(III) chloride
(iv) Amminebromidochloridonitrito-N-platinate(II)
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(iv) 4-Oxopentanal
(v) Di-sec-butyl ketone
(vi) 4-Fluoroacetophenone
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(i) 2-Chloro-3-methylpentane
(ii) 1-Chloro-4-ethylcyclohexane
(iii) 4-tert. Butyl-3-iodoheptane
(iv) 1,4-Dibromobut-2-ene
(v) 1-Bromo-4-sec. butyl-2-methylbenzene
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