The reaction involves a Grignard reagent (RMgBr) reacting with CO₂, followed by acid hydrolysis. This is a standard method to prepare carboxylic acids. The Grignard reagent acts as a nucleophile, attacking the electrophilic carbon of CO₂. After nucleophilic addition, acid workup protonates the resulting carboxylate anion to give the carboxylic acid. The general reaction is:

$$\begin{gathered} R-\mathrm{MgBr}+\mathrm{CO}2 \\ \to \\ \mathrm{RCOO}{}^{-}{\mathrm{MgBr}}^{+} \\ \stackrel{H3O^{+}}{\to } \\ \mathrm{RCOOH} \end{gathered}$$

Therefore, the final product is a carboxylic acid with one more carbon atom than the original alkyl/aryl group (R) of the Grignard reagent.

Final Answer: Carboxylic Acid