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

(i) Eq. wt. of Cr `=("Atomic weight")/("Change of oxidation number per mole")=(52)/(6)`
96500 coulomb deposit `=(52)/(6)` gm (Cr)
24000 coulomb will deposite `=(52)/(6) xx (2400)/(96500)gm =2.1554` gm of Cr
`W_(Cr)=1.5gm i=12.5"ampere"`
`E_(Cr)=(52)/(6), t=?`
`W=("Eit")/(96500) rArr 1.5 =(52 xx 12.5 xx t)/(6 xx 96500)`
t=1336.15 second