Question

Aluminium carbide on hydrolysis gives a compound 'X'. X can also be prepared by:
1. Hydrogenation of olefines
2. kolbe's electrolysis
3. decarboxylation
4. Wurtz reaction

Answer 1

Correct Answer - Option 3 : decarboxylation

Concept -

Hydrolysis of aluminium carbide: 

• Hy­drol­y­sis is a reaction that occurs between a substance and water, resulting in the breakdown of the substance and the formation of new compounds.
• Al₄C₃ is a salt-like car­bide that is essen­tial­ly the result of met­al atoms dis­place­ing the hydrogen atom in meth­ane.
• Reverse dis­place­ment occurs easily in its hy­drolysis, and meth­ane forms.
• When a water molecule is added to the aluminium carbide molecule, both the water molecule and the reactant molecule split in the reaction.
• Alu­minum car­bide hy­drol­y­sis is an irreversible re­action.
• Meth­ane and alu­minum hy­drox­ide are released during this re­ac­tion.
• This re­ac­tion is a simpl­i­fied way to get meth­ane in the lab­o­ra­to­ry.

Al₄C₃ + 12H₂O → 4Al(OH) ₃ + 3CH₄ 

Decarboxylation reaction to obtain methane - 

• A decarboxylation reaction is a chemical reaction in which a carboxyl group is removed.
• It is a process in which carboxylic acids remove a carbon atom from a carbon chain.
• Heating carboxylic acid sodium salts with soda lime (a combination of sodium hydroxide and calcium oxide) produces methane with one less carbon atom than the carboxylic acid.                                    

CH₃COO^-Na⁺ + NaOH → CH₄ + Na₂CO₃ 

 (in the presence of CaO and heat)

Explanation - 

• The product 'X' released after the hydrolysis of aluminium carbide is methane. 
• Methane can be produced with the hydrolysis of aluminium carbide as well as through decarboxylation reaction.
• Decarboxylation - Acetic acid salt on heating with soda lime gives our pure methane. 

Hence, the correct answer to this question is Decarboxylation, another method that can be used to prepare methane.