Chromium metal can be plated out from an acidic solution containing `CrO_(3)` according to following equation,
`CrO_(3(aq.))+6H^(+)+6e rarr Cr_((s))+3H_(2)O`
Calculate :
(i) How many gram of chromium will be plated out by 2400 columb ?
(ii) How long will it take to place out 1.5g Cr by using 12.5 ampere current ?

Explanation

WE known,
Eq. wt. of
`Cr=("At.wt")/("No.of electrons lost or gained by one molecule of Cr")=(52)/(6)`
(i) `because 96500` coluomb deposit `=(52)/(6)g Cr`
`therefore 24000` coluomb deposit
`=(52)/(6)xx(24000)/(96500)=(52)/(6)xx(24000)/(96500)=2.1554g` of Cr
(ii) Also given, `w_(Cr)=1.5g , i = 12.5` ampere , t = ? `E_(Cr)=52//6`
`therefore w=("E.i.t")/(96500)`
`1.5=(52xx12.5xxt)/(6xx96500)=1336.15` second