Question

$Cd$ amalgam is prepared by electrolysis of a solution of $CdC{l}_2$ using a mercury cathode. Current of how much ampere must be passed for $100$ seconds in order to prepare $20\%Cd-Hg$ amalgam on a cathode of $2g$ mercury? (At. wt. of $Cd=112.40$)

• A. $34.32$ ampere
• B. $8.58$ ampere
• C. $4.29$ ampere
• D. $17.16$ ampere

Answer 1

Answer: (B)

$20\%Cd-Hg$ amalgam means $80gHg$ has $20gCd$
$\therefore 2gHg$ require $=\frac{20}{80}\times =0.5gCd$
$C{d}^{2+}+2e^{-}\to Cd$
eq. wt. of $Cd=\frac{112.4}{2}$
Applying, $W=Z\times I\times t$
$Z=\frac{eq.wt}{96500}$
$I=0.5\times 96500\times \frac{2}{112.4}\times \frac{1}{100}=8.58$ ampere