The Gibbs energy for the decomposition of

Question:

The Gibbs energy for the decomposition of $\mathrm{Al}_{2} \mathrm{O}_{3}$ at $500{ }^{\circ} \mathrm{C}$ is as follows : $\frac{2}{3} \mathrm{Al}_{2} \mathrm{O}_{3} \longrightarrow \frac{4}{3} \mathrm{Al}+\mathrm{O}_{2}, \Delta_{\mathrm{I}} \mathrm{G}=+966 \mathrm{KJ} \mathrm{mol}^{-1}$ The potential difference needed for electrolytic reduction of $\mathrm{Al}_{2} \mathrm{O}_{3}$ at $500^{\circ} \mathrm{C}$ is at least :-

  1. 5.0 V 

  2. 4.5 V

  3. 3.0 V

  4.  2.5 V


Correct Option: , 4

Solution:

$966 \times 10^{3}=4 \times 96500 \times \mathrm{E} \Rightarrow \mathrm{E}=2.5 \mathrm{~V}$

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