Molten aluminim chloride is electrolysed with a current of 0.5 ampere to produce 27.0 g of aluminium.
(a) How many gram equivalents of aluminium were producted ?
(b) How long did the electrolysis take place ?
(c ) How many litres of chlorine were evolved at S.T.P. ?

Answer

(a)3 g `equiv^(-1)` (b) 160.83 hr (c ) 33.6 L

Explanation

The electrolysis of molten aluminium chloride is represented as :
`AlCl_(3)hArrAl^(3+)(l)+3Cl^(-)(l)`
`Al^(3+)(l)+3e^(-) to Al(s) , 3Cl^(-)(l) to 3//2 Cl_(2)(g)+3e^(-)`
(a) Gram equivalent of aluminium deposited
`=("Mass of Al deposited")/("Equivalent mass of" Al)=(27g)/((9equiv^(1)))=3 g equiv^(-1)`.
(b) Time for which electrolysis was carried :
`Al^(3+)(l)+underset((3 Faraday))3e^(-) to underset((27 g))Al(s)`
Let the current be passed for time =t sec.
`:." "` Quantity of charge (Q) passed`=(0.5 amp)xxt(s)=0.5xxt(C)`
Actual amout of charge passed`=3F=3xx96500" C"`
`:.` Time (t) for which electrolysis was carried `=(3xx96500(C))/(0.5(C))=579000 s=(579000)/(60xx60)=160.83` hr.
(c ) Litres of chlorine evolved :
`3Cl^(-) to underset(3//2xx22.4 L) Cl_(2)(g)+underset(3F)(3e^(-))`
=33.6 L
3 Faraday of charge will evolve `Cl_(2)`(g)=33.6 L.