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Activity Series (OR) Electro chemicals series

Question

An aqueous solution containing one mole per litre of each Cu(NO₃)₂, AgNO₃. Hg(NO₃)₂, Mg(NO₃)₂ is being electrolysed using inert electrodes. The values of standard electrode potential in volts (reduction potential) are
Ag / Ag⁺ = + 0.80V Hg²⁺ / Hg = + 0.79V
Cu²⁺ / Cu = + 0.34V Mg²⁺ / Mg = – 2.37V
With increasing voltage, the sequence of deposition of metals on cathode will be

Moderate

A

Ag, Hg, Cu, Mg
B

Mg, Cu, Hg, Ag
C

Ag, Hg, Cu
D

Cu, Hg, Ag

Solution

At Cathode higher reduction potential is reduced first.Mg reduces all the three metals because it is having lowest SRP.
Cu reduces Hg²⁺ to Hg and also reduces Ag⁺ to Ag.
Hg reduces only Ag⁺ to Ag.
Mg²⁺is not reduced because there is no element given with lower SRP.
Order of deposition is
Cu < Hg < Ag.

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