Question

In the Castner process for the extraction of sodium, the anode is made up of ………… metal.
a.) Copper
b.) Carbon
c.) Sodium
d.) Nickel

Answer 1

Hint: It is a metal from d-block elements. This metal is used extensively to make coins and nickel steel for armor plates and burglar-proof vaults and is also a component in Nichrome and constantan. Now try to find the correct answer.

Complete step by step answer:

Let us talk about the complete process of manufacturing sodium metal.

Castner process - Castner process is a process of manufacturing sodium metal from sodium hydroxide at 330-degree celsius. In this process anode is made of Nickel and cathode is made of Iron.
Below 330-degree Celsius temperature, the metal would solidify; above that temperature, the metal would start to dissolve in the melt.
A ceramic crucible with a steel cylinder suspended within is used for this process. Both cathode and anode are made of iron or nickel as we have already discussed.
The temperature is cooler at the bottom and hotter at the top so that the sodium hydroxide is solid in the neck and liquid in the body of the vessel.
Sodium metal forms at the cathode but is less dense than the fused sodium hydroxide electrolyte. Wire gauze confines the sodium metal to accumulate at the top of the collection device.
The cathode reaction is
$2N{a}^{+}+2e^{-}\to 2Na$
The anode reaction is
$2O{H}^{-}\to ½O^2+H_{2}O+2e^{-}$
Despite the elevated temperature, some of the water produced remains dissolved in the electrolyte. This water diffuses throughout the electrolyte and results in the reverse reaction taking place on the electrolyzed sodium metal.
$Na+H_{2}O\to ½H_2+N{a}^{+}+O{H}^{-}$
with the hydrogen gas also accumulating, this, of course, reduces the efficiency of the process.

Therefore, we can conclude that the correct answer to this question is option D.

Note: You should not confuse yourself with Castner–Kellner process. The Castner–Kellner process is a method of electrolysis on an aqueous alkali chloride solution (usually sodium chloride solution) to produce the corresponding alkali hydroxide, invented by American Hamilton Castner and Austrian Karl Kellner in the 1890s.