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Given below are two statements : 1. M aqueous solutions of each of Cu(NO3)2, AgNO3, Hg2(NO3)2, Mg(NO3)2 are electrolysed using inert electrodes. Given : E°Ag+/Ag = 0.80 V and E°Hg2^2+/Hg = 0.79 V, E°Cu2+/Cu = 0.24 V and E°Mg2+/Mg = -2.37 V Statement I : With increasing voltage, the sequence of deposition of metals at the cathode will be Ag, Hg and Cu. Statement II : Magnesium will not be deposited at cathode instead oxygen gas will be evolved at the cathode. In the light of the above statements, choose the most appropriate answer from the options given below.

1. Statement I is incorrect but Statement II is correct
2. Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Both Statement I and Statement II are correct

Correct answer: Both Statement I and Statement II are correct

Solution

Statement I is correct because the metals will deposit at the cathode in the order of their standard reduction potentials, with silver (Ag) having the highest potential followed by mercury (Hg) and copper (Cu). Statement II is also correct as magnesium has a very low reduction potential, making it less likely to be deposited; instead, water will be oxidized to produce oxygen gas at the cathode.

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