KVPY Sample Paper KVPY Stream-SX Model Paper-14

Zn Amalgam is prepared by electrolysis of aqueous\[ZnC{{l}_{2}}\]using Hg cathode (9gm). How much current is to be passed through\[ZnC{{l}_{2}}\]solution for 1000 seconds to prepare a Zn Amalgam with 25% Zn by wt.\[(Zn=65,\,\,4)\]

A) 5.6 amp

B) 7.2 amp

C) 8.85 amp

D) 11.2 amp

Correct Answer: C

Solution :

Let x gm of Zn deposit on 9 gm of Hg

% of Zn in Amalgam\[=\frac{{{m}_{Zn}}\times 100}{{{m}_{Zn}}+{{m}_{Hg}}}=\frac{x}{9+x}\times 100=25\]

\[\therefore \] \[x=3\,gm\]

Eq. of \[Zn=\frac{3\times 2}{65.4}\]

\[\frac{{{n}_{Zn}}}{1}=\frac{{{n}_{{{e}^{-}}}}}{2}=\frac{Q}{2f}=\frac{it}{2f}\]

Current \[i=\frac{6}{65.4}\times \frac{96500}{1000}=8.85\,amp.\]