Question

When electricity is passed through an aqueous solution of brine, it decomposes to form 'X'. This process is called 'Y' becuase of the products formed. Products 'Z' and 'W' are formed at the cathode and the anode respectively. Identify, X, Y, Z and W.

• A. X - Sodium hydroxide Y- Chlor-alkali Z - Hydrogen W - Chlorine
• B. X - Hydrogen Y- Chlor-alkali Z - Chlorine W - Sodium hydroxide
• C. X -Chlorine Y -Sodium hydroxide Z- Hydrogen W -Chlor-alkali
• D. X -Sodium hydroxide Y-Hydrogen Z-Chlorine W -Chlor-alkali

Answer 1

The correct option is A

X - Sodium hydroxide Y- Chlor-alkali Z - Hydrogen W - Chlorine

It is the chlor-alkali process, and is called so, as chlorine and sodium hydroxide (caustic soda, an alkali) are produced by the electrolysis of NaCl soln. (brine soln.). The cathode products are NaOH and $H_2$ while the anode product is Chlorine.
For a Chlor- Alkali process:
$Anodereaction:C{l}^{-}\left(aq\right)\to C{l}_2+e^{-}$ $Cathodereaction:N{a}^{+}\left(aq\right)+H_{2}O+e^{-}\to NaOH+\frac{1}{2}{H}_2$ $Overallreaction:NaCl\left(aq\right)+H_{2}O\to NaOH+\frac{1}{2}{H}_2+\frac{1}{2}C{l}_2$