The Gibbs energy for the decomposition of `Al_(2),O_(3)` , at `500^(@)` C is as follows:
`2/3 AI_(2)O_(3)rarr 4/3 AI+O_(2), triangle_(r )G =|966 kj mol^(-1)` The potential difference needed for the electrolytic reduction of `AI_(2)O_(3)` at `500^(@)` C is at least:

Options

A. -2.5 V
B. +5.0 V
C. 4.5 V
D. 3.0 V

Answer

A

Explanation

In the given reaction `2/3[2A^(3+)]+4e rarr 4/3 AI (n=4)`
`therefore triangleG==nFE,E=(triangleG)/(nF)=(966xx100)/(4xx96500)=-2.5 V`