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Question
How many faradays of electricity are required to produce 13 gram of aluminium from aluminium chloride solution? (Given: Molar mass of Al = 27.0-gram mol–1)
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Solution
AlCl3 
Al+3 + 3Cl-
Al+3 + 3e- Al
1 mole of Al requires passage of 3 moles of electrons. The charge on 3 moles of e- is 3 Faraday.
Moles of Al produced = `"mass of Al"/"molar mass of Al"`
= `13/27`
= 0.48 moles
As 3F of electricity produces 1 mole of Al
∴ No. of faradays of electricity required to produce 0.48 mole of Al
= 0.48 x 3
= 1.44 Faraday
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