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A solution containing one mole per litre each of $Cu(NO_3)_2,AgNO_3,Hg_2(NO_3)_2,Mg(NO_3)_2$ is being electrolysed by using inert electrodes.The values of standard potentials are $E^0_{Ag^+/Ag}=0.8V$,$E^0_{Hg^{+2}/Hg}=0.79V$,$E^0_{Cu^{+2}/Cu}=0.34V$,$E^0_{Mg^{+2}/Mg}=-2.3V$ with increasing voltage the sequence of deposition of metals on the cathode will be

$\begin{array}{1 1}(a)\;Ag,Hg,Cu,Mg\\(b)\;Mg,Cu,Hg,Ag\\(c)\;Ag,Hg,Cu\\(d)\;Cu,Hg,Ag\end{array}$

1 Answer

The metal ions will be get preferentially deposited on the cathode in order of their decreasing reduction potentials.The order of deposition of metal will be Ag,Hg and Cu.Mg will not be deposited because $H^+$ will be preferentially discharged.
Hence (c) is the correct answer.
answered Feb 17, 2014 by sreemathi.v

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