Question

Explain how a very reactive metal like sodium is extracted from common salt?

Answer 1

Hint: As we know that sodium is a very reactive and an important alkali metal. It is usually extracted from a common salt that is sodium chloride (NaCl) by using Down’s method. This method is based on the electrolysis of fused NaCl. So here we have to explain regarding the extraction of sodium metal from common salt.

Complete answer:
Let us discuss about sodium followed by its extraction from common salt as follows:-
-Sodium: It is a chemical element denoted by symbol Na and has atomic number 11. It is usually a soft, silvery-white metal which is highly reactive in nature. It is an alkali metal and belongs to group 1 of the periodic table. It is industrially extracted from common salt by using Down’s method.
-Extraction of sodium metal by using Down’s method:-
This method is generally based on the electrolysis of fused NaCl. This method involves the usage of Down’s cell which consists of a rectangular container of steel like a tank which is lined by firebricks. Here the anode is graphite which projects centrally up through the base of the cell and the cathode is an iron ring (around the anode). Both anode and cathode are separated from each other by a cylindrical steel gauze diaphragm in order to keep sodium metal and chlorine gas apart.
A mixture of sodium chloride (NaCl) and calcium chloride ($CaC{l}_2$) is electrolyzed in down's cell where the composition of NaCl is 42% and $CaC{l}_2$ is 58%.
When electric current is passed through the mixture, sodium chloride decomposes to sodium and chloride ions. Sodium ions ($N{a}^{+}$) migrate toward the cathode (negative electrode) and chloride ions ($C{l}^{-}$ ) migrate towards the anode. We can collect molten sodium at anode and chlorine gas at cathode.
The reaction takes place as follows:-
$2NaCl\to 2N{a}^{+}+2C{l}^{-}$
At cathode: $2N{a}^{+}+2e^{-}\to 2Na$
Sodium ions get reduced at cathode to form sodium metal.
At anode: $2C{l}^{-}\to C{l}_2+2e^{-}$
Chloride ions get oxidized at anode to form chlorine gas.

Note:
-Remember that mixture of NaCl and $CaC{l}_2$is used because melting point of NaCl is 801${}^{\circ }C$ and at this temperature sodium chloride and sodium metal can form a metallic fog in the container which is impossible to separate. Therefore we used the above mixture as the melting point of the mixture is 600${}^{\circ }C$.