Name: Biological Importance of Na and K
Uploaded: 2019-07-19
Duration: 4 min 59 s
Description: Sodium and Potassium are important alkali metals that have many industrial applications. But, they play a vital role in the human body, as well. Let’s watch...

Question

What do you know about Castner-Kellner process? Write the principle involved in it.

Accepted Answer

The principle of Castner-Kellner cell: In this process, an aqueous alkali chloride solution (usually sodium chloride solution) is electrolysed to produce the corresponding alkali hydroxide.

The electrodes used are: Mercury as cathode and carbon as anode.

Process:- When electric current is passed through brine (aqueous sodium chloride solution), positive and negative ions migrate towards their respective electrodes. ${Na}^{+}$ ions are discharged at mercury cathode. The sodium deposited at mercury forms $Na - Hg$ amalgam. Chlorine produced at the anode is removed from the top of the cell.

At Cathode : ${Na}^{+} (aq) + e^{-} \to Na (s)$ (amalgam)

At Anode : ${Cl}^{-} (aq) \to \frac{1}{2} {Cl}_{2} (g) + e^{-}$

The advantage of using $Hg$ as a cathode is that, the discharge potential of ${Na}^{+}$ ions is less than that of $H^{+}$ . ${Na}^{+}$ ions get discharged on mercury and sodium so deposited combines with mercury to form sodium amalgam flows out and treated with water to give sodium hydroxide and hydrogen gas.

$\underset{Amalgam}{2 Na - Hg (l)} + 2 H_{2} O (l) \to 2 NaOH (aq) + 2 Hg (l) + H_{2} (g)$

During electrolysis, hydrogen is evolved at cathode and chlorine is evolved at anode, which are the by product of this process. The mercury produced in last step is recycled.

What do you know about Castner-Kellner process? Write the principle involved in it.

Important Questions on The s -Block Elements

Learn and Prepare for any exam you want !