Question

$Cd$ amalgam is prepared by electrolysis of a solution of $CdCl_{2}$ 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 $2 g$ 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 $80 \,g \,Hg$ has $20 \,g\, Cd$
$\therefore 2g Hg$ require $= \frac{20}{80} \times = 0.5 \,g\, Cd$
$Cd^{2+} +2e^{-} \to Cd$
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