COMEDK 2025 Afternoon Solved Paper

Concept:Acetic acid reacts with $\mathrm{HI}$ and red phosphorus at $473 \, \mathrm{K}$ to give iodomethane (methyl iodide), not iodoethane.Explanation:In the presence of red phosphorus and $\mathrm{HI}$, acetic acid undergoes decarboxylation.The reaction proceeds as:$P + I_2 \longrightarrow PI_3$$CH_3COOH + PI_3 \xrightarrow{473 \, \mathrm{K}} CH_3I + CO_2 + H_3PO_3$Thus, the product is iodomethane ($\mathrm{CH_3I}$), not iodoethane ($\mathrm{C_2H_5I}$).Hence, option A is incorrect.Check the other statements:Acetic acid ($pK_a \approx 4.75$) is weaker than formic acid ($pK_a \approx 3.75$). So B is correct.Acetic acid reacts with aqueous $\mathrm{NaHCO_3}$ to produce $\mathrm{CO_2}$ gas, causing effervescence. So C is correct.Acetic acid is a weak acid and does not reduce Fehling's solution (only aldehydes or $\alpha$-hydroxy ketones reduce it). So D is correct.Answer:Option A is the incorrect statement.