`Al_(2)O_(3)` is reduced by electrolysis at low potentials and high current. If `4.0 xx 10^(4)` amperes of currernt is passed through molten `Al_(2)O_(3)` for 6 hours, what mass of aluminium is produced? (Assume 100 % current efficiency, At. Mass of `Al = 27 u`)

Options

A. `9.0xx10^(3)g`
B. `8.1xx10^(4) g `
C. `2.4xx10^(5) g`
D. `1.3xx10^(4) g`

Answer

B

Explanation

(b) `Al_(2)O_(3)` ionises as,
`Al_(2)O_(3) iff underset("Cathode")(Al^(3+))+underset("Anode")(AlO_(3)^(3-)`
At cathode
`Al^(3+) + underset(3F)(3e^(-)) to underset(27 g)(Al)`
`:.` Mass of aluminium deposited by 3F of electricity =27g
`:.` Mass of aluminium deposited by `4.0xx10^(4)xx6xx3600 C` of electricity
`=(27xx4.0xx10^(4)xx6xx3600)/(3F) g `
`=(27xx4.0xx10^(4)xx6xx3600)/(3xx96500) g `
`=8.1xx10^(4)g`