Question

In Kolbe’s electrolysis reaction:
(A) ${{H}_{2}},C{{O}_{2}}$ are liberated at cathode
(B) Hydrocarbon, $C{{O}_{2}}$ are liberated at anode
(C) pH of the solution increases
(D) aq. Solution of sodium acetate forms ethane

Answer 1

Hint: When Kolbe’s electrolysis is carried, then electrochemical decarboxylation of sodium or potassium salts of carboxylic acid take place. Now, by using this we can easily answer the given question.

Complete answer:
- Kolbe’s electrolysis is basically an organic reaction which is also known as decarboxylation dimerization, since the reaction proceeds with radical reaction mechanism and evolution of carbon dioxide takes place.
- In this method, the decarboxylation of sodium or potassium salts of carboxylic acids takes place and are converted into their corresponding alkanes.
-It involves the formation of symmetrical hydrocarbons through the coupling of radicals generated from carboxylic acid at an anode via electrolysis.
- Kolbe’s electrolysis reaction has been modified to occur in liquid ammonia and is known to be useful for the preparation of hydrocarbons.
- Using this electrolysis process, the aqueous solution of sodium acetate is electrolysed, i.e. the acetate ions get decomposed and form methyl radicals. These combine with other free methyl radicals which leads to the generation of ethane.
- After completing the reaction, the solution becomes alkaline, and so, the pH will increase.

Therefore, we can easily conclude that option (B), (C), and (D) are correct answers to the given question.

Note: It should be recalled that this method is not used for the preparation of methane or alkanes having odd numbers of carbon atoms. Furthermore, during electrolysis, pH of electrolyte increases gradually due to the formation of alkalis.