question_answer

The Gibbs’ energy for the decomposition of\[A{{l}_{2}}{{O}_{3}}\] at \[{{500}^{o}}C\] is as follows

\[\frac{2}{3}A{{l}_{2}}{{O}_{3}}\xrightarrow[{}]{{}}\frac{4}{3}Al+{{O}_{2}};\] \[{{\Delta }_{r}}G=+\,960\,kJ\,mo{{l}^{-1}}\]

The potential difference needed for the electrolytic reduction of aluminium oxide \[(A{{l}_{2}}{{O}_{3}})\] at \[{{500}^{o}}C\] is at least             [AIPMT (M) 2012]

A)  4.5 V             

B)       3.0 V   

C)  2.5 V                  

D)       5.0 V

Correct Answer: C

Solution :

The half cell reaction are             at anode                         At cathode            

Net reaction

or

Here,

Potential difference