Question

Which of the following metals are obtained by electrolysis of their chlorides in a molten state?$\left(\mathrm{i}\right)\mathrm{Na}\left(\mathrm{ii}\right)\mathrm{Ca}\left(\mathrm{iii}\right)\mathrm{Fe}\left(\mathrm{iv}\right)\mathrm{Cu}$

• A. (i) and (iv)
• B. (iii) and (iv)
• C. (i) and (iii)
• D. (i) and (ii)

Answer 1

The correct option is D

(i) and (ii)

Explanation for correct option:

D. (i) and (ii)

Electrolysis

• It is a process that leads to chemical change when an electric current is passed through an electrolyte.
• During the electrolysis process, the negatively charged electrode loses the electrons and undergoes oxidation while the positively charged electrode gains the electrons and undergoes the reduction process.
• Sodium and calcium are obtained by electrolysis of their chlorides in a molten state.
• Both are reactive metals.

Electrolysis of molten sodium chloride:

• During electrolysis of molten sodium chloride.
• The chemical reactions at anode and cathode can be depicted as:

$$\begin{gathered} \mathrm{At}\mathrm{anode}:\hspace{0.17em}2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)\to {\mathrm{Cl}}_2\left(\mathrm{g}\right)+2{\mathrm{e}}^{-} \\ \mathrm{At}\mathrm{cathode}:\hspace{0.17em}2{\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}\to 2\mathrm{Na}\left(\mathrm{s}\right) \end{gathered}$$

• The overall reaction can be depicted as:

$2\mathrm{NaCl}\left(\mathrm{l}\right)\to 2\mathrm{Na}\left(\mathrm{s}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)$

The explanation for incorrect options

(iii) Fe

Iron is moderately reactive. So, iron is extracted by reduction of its oxides using carbon.

(iv) $\mathrm{Cu}$

$\mathrm{Cu}$ is present in the form of sulfide ores and cannot be obtained by electrolysis of their chlorides.

Hence, the correct option is D i.e. (i) and (ii). Metals that are obtained by electrolysis of their chlorides in a molten state are sodium and calcium.