Sodium hydroxide is prepared commercially from sodium chloride solution by?

Dave333

4 years ago

(i) Sodium hydroxide is prepared commercially by the electrolysis of brine solution in Castner- Keller cell. (iii) Sodium metal is discharged at the cathode and combines with mercury to form sodium amalgam. Chlorine gas is evolved at the anode.

abbaausain

2 years ago

The correct answer is A.

Explanation:
Sodium hydroxide, also known as caustic soda, is commonly prepared from sodium chloride, or common table salt, through a process called the Chloralkali process. This process employs electrolysis, a method where electric current is passed through a solution to cause a chemical change.

During this process, the sodium chloride solution is electrolyzed using mercury as a cathode. Here's a simplified version of what happens:

At the anode (positive electrode), chloride ions are oxidized to form chlorine gas. This can be represented by the half-equation:
2
C
l
−
→
C
l
2
+
2
e
−
.

At the cathode (negative electrode), sodium ions are reduced and amalgamate with mercury to form a sodium-mercury amalgam. The half-equation for this reaction is:
N
a
+
+
e
−
→
N
a
.

The sodium-mercury amalgam then reacts with water to form sodium hydroxide and hydrogen gas, thus producing the desired product, sodium hydroxide.

Note that mercury is used as the cathode due to its unique properties: it can dissolve certain metals, like sodium, to form an amalgam, which then reacts with water to produce sodium hydroxide.

The other options listed, such as hydrolysis in steam using a catalyst, using iron as an anode, or treating sodium chloride with ammonia and carbon (IV) oxide, are not typically used in the commercial production of sodium hydroxide.