The basicity of CH3COOH is

Analysis

The question asks for the basicity of ethanoic acid ($CH_3COOH$). In chemistry, the basicity of an acid refers to the number of replaceable hydrogen ions ($H^+$) that one molecule of the acid can release in an aqueous solution.

Concept Explanation

• Basicity of an acid: This is determined by the number of ionizable hydrogen atoms present in the carboxyl group ($-COOH$) of an organic acid.
• Structure of Ethanoic Acid ($CH_3COOH$): Although the formula contains four hydrogen atoms, only the hydrogen atom attached to the oxygen in the carboxyl group ($-COOH$) is acidic. The three hydrogen atoms attached to the carbon atom ($CH_3-$) are covalently bonded and do not dissociate in water.
• Dissociation: When ethanoic acid dissolves in water, it ionizes as follows: $$CH_3COOH_{(aq)} \rightleftharpoons CH_3COO^-_{(aq)} + H^+_{(aq)}$$Since only one$H^+$ ion is produced per molecule, the acid is monobasic.

Step-by-Step Solution

1. Identify the functional group: Ethanoic acid belongs to the carboxylic acid family, characterized by the $-COOH$ group.
2. Determine ionizable hydrogens: In carboxylic acids, only the hydrogen in the $-COOH$ group is replaceable by a metal or a base.
3. Count the replaceable hydrogen: There is only one such hydrogen atom in $CH_3COOH$.
4. Conclusion: Since it releases only one $H^+$ ion, its basicity is 1.

Identifying the Answer

Comparing our result to the given options: A. 4 B. 1 C. 2 D. 3

The correct option is B.

Exam Tip

Always remember: Basicity is for acids (number of $H^+$), and Acidity is for bases (number of $OH^-$). For organic acids like $CH_3COOH$, $HCOOH$, or $C_2H_5COOH$, the basicity is almost always 1 because they only contain one $-COOH$ group. Don't be tricked by the total number of hydrogen atoms in the formula!