Question

(a) Here is an electrode reaction :

$Cu\to C{u}^{2+}+2e^{-}$. At which electrode (anode or cathode) would such a reaction take place? Is this an example of oxidation or reduction ?

(b) A solution contains magnesium ions $\left(M{g}^{2+}\right)$, iron (II) ions $F{e}^{2+}$ and copper ions $C{u}^{2+}$. On passing an electric current through this solution, which ions will be the first to be discharged at the cathode? Write the equation for the cathode reaction.

(c) Why is carbon tetrachloride, which is a liquid, a non-electrolyte ?

(d) During the electrolysis of molten lead bromide, which of the following takes place ?

A. Bromine is released at the cathode,

B. Lead is deposited at the anode,

C. Bromine ions gain electrons,

D. Lead is deposited at the cathode.

Answer 1

(a) Cu(0) is changing to copper(+2) , thus there is loss of electrons. Loss of electrons refers to oxidation.
This reaction occurs at anode.

(b) Metals down in the reactivity will be discharged at cathode because at cathode gain of electrons occur. Least reactive metal have greater tendency to gain electrons. $C{u}^{2+}$ will be discharged at cathode.

$C{u}^{2+}$ + 2$e^{-1}$ $\Rightarrow$ Cu

(c)Carbon tetrachloride neither dissociates into ions nor induces ion formation in the solvent. The reason is that the C − C l bond is rather strong and won't break under normal solution conditions.

(d) Option d is the correct answer.
lead is a metal thus its ion will be positively charged, hence it will be relesed at the cathode.