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Cd amalgam is preapred by electrolysis o...

Cd amalgam is preapred by electrolysis of a solution `CdCI_(2)` using a mercury cathode. How long should a current of `5A` be passed in order to prepare `12% Cd-Hg` amalgam on a cathode of `2g, Hg`( atomic weight of `Cd = 112.4)`

Text Solution

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The correct Answer is:
`t = 93.65 sec`
`2mg` of Hg contains `= (12)/(88) xx 2` gm of Cd
`= 0.27gm` of Cd
`Cd^(+2) +2e^(-) rarr Cd`
`n_(Cd^(+2)) = (0.27)/(112.4) n_(E) = (2 xx 0.27)/(112.4)`
`I = (q)/(t)`
`t = (2 xx 0.27)/(112.4) xx (96500)/(5)`
`t = 93.653`
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Chemical reactions involve interation of atoms and molecules. A large number of atoms // molecules ( approximately 6.023xx10^(23)) are present in a few grams of any chemical compound varying with their atomic // molecular masses. To handle such large numbers conveniently, the mole concept was introduced. This concept has implications in diverse areas such as analytical chemistry, biochemistry, electrochemistry, and radiochemistry. The following example illustrates a typical case, involving chemical // electrochemical reaction, which requires a clear understanding of the mole concept. A 4.0M aqueous solution of NaCl is prepared and 500mL of this solution is electrolyzed. This leads to the evolution of chlorine gas at one of the electrodes ( atomic mass of Na is 23 and Hg is 200)(1F=96500C) . If the cathode is an Hg electrode, the maximum weight (in g) of amalgam formed from this solution is