Question

Select the correct answer from the choices a, b, c and d which are given.
Write only the letter corresponding to the correct answer.
(i) A compound which liberates reddish brown gas around the anode during the electrolysis in its molten state is:
(a) Sodium chloride
(b) Copper (II) oxide
(c) Copper (II) sulphate
(d) Lead (II) bromide

(ii) During ionization metals lose electrons, this change can be called:
(a) Oxidation
(b) Reduction
(c) Redox
(d) Displacement

Answer 1

(i) (d) Lead (II) bromide
Reaction at anode: Bromide ions lose 2 electrons to anode and get oxidised to bromine atoms, that combine together to form red vapours of bromine molecule at anode.
$$\begin{gathered} 2{\mathrm{Br}}^{-}\stackrel{\mathrm{Oxidation}}{\to }{\mathrm{Br}}_2+2{\mathrm{e}}^{-} \\ (\mathrm{Bromine}\mathrm{molecule}) \end{gathered}$$

(ii) (a) Oxidation
Metals lose electrons and get oxidised to cations. For example, the reaction :
$\mathrm{K}\stackrel{}{\to }{K}^{+}+e^{-}$
is an oxidation reaction. Here, potassium metal loses one electron and gets oxidised to potassium ion.