Electrochemistry Test - 10

The dry cell contains a conducting solution (electrolyte) of ammonium chloride, a cathode (positive terminal) of carbon, a depolariser of manganese dioxide, and an anode (negative terminal) of zinc.

During the electrolysis of NaCl, if we use Pt electrode, then H₂ is liberated at cathode; while in the presence of Hg cathode, it forms sodium amalgam because at Hg, more voltage is required to reduce H⁺ than at Pt electrode.

The reaction is Cu²⁺(aq) + 2e^– → Cu(s), i.e. 1 mol of Cu is deposited by 2 moles of electrons.

For the deposition of 6.35 g Cu (= 0.1 mol Cu), 0.2 mol of electrons will be needed.
The deposition of Ag(s) involves the reaction: Ag⁺(aq) + e^– → Ag(s).

Thus, for 0.2 mol of electrons, 0.2 mol of Ag will be deposited, which is 0.2 x 108 g, i.e. 21.6 g.

The reaction that occurs at the anode is as follows:
Cu(s) → Cu⁺²(aq) + 2e^-
Thus, 3.15 g of Cu from the anode dissolves and comes into the electrolyte and hence, the mass of the anode decreases.

To prevent rusting of iron, it is coated with more reactive white tin because it has lower reduction potential than iron and has greater oxidising power.

The lower the reduction potential, the higher is the oxidising power.