See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Concept: Isotope tracking in chemical reactions. In this reaction, benzoic acid reacts with sodium bicarbonate (NaHCO3) where the carbon in NaHCO3 is isotopically labeled (marked with asterisk *). The reaction is: C6H5COOH + NaHCO3* --> CO2 + C6H5COONa + H2O. Step 1: Identify which carbon is labeled. The asterisk (*) is on the carbon of NaHCO3 (the bicarbonate carbon, i.e., the C in HCO3-). Step 2: Trace where the labeled carbon goes. In this acid-base reaction, the carboxylic acid (C6H5COOH) donates a proton to HCO3-, forming H2CO3 which decomposes to CO2 + H2O. The carbon from NaHCO3* becomes CO2. The carbon from benzoic acid's -COOH group goes into sodium benzoate (C6H5COONa). Step 3: Therefore, the labeled carbon C* ends up in CO2 (option a), not in sodium benzoate. Step 4: Why other options fail: Option (b) is wrong because the COONa carbon originates from the original benzoic acid, not from NaHCO3*. Option (c) is wrong because C* is only in CO2. Option (d) is wrong because C* is indeed with CO2. Therefore, the correct answer is A.