The time required to coat a metal surface of `80 cm^(2)` with `5 xx 10^(-3) cm` thick layer of silver (density `1.05 g cm^(-3)`) with the passage of `3A` current through a silver nitrate solution is:

Options

A. 115 sec
B. 125 sec.
C. 135 sec.
D. 145 sec.

Answer

B

Explanation

`a=80cm^2, l=5xx10^(-3) cm^3`
`therefore V=80xx5xx10^(-3) cm^3 =0.4 cm^3`
`d=1.05 g//cm^3 therefore W=d.V=10.5xx0.4=0.420 gm`
then W=Zit =`(E)/(F) =It`
`therefore 0.42 =(108)/(96500) xx3xxt`
` therefore t=125 sec`