Final answer:
Baking soda contains the bicarbonate group, not the carboxyl group, which includes a carbon atom double-bonded to an oxygen and also bonded to a hydroxyl (-OH) group.
Step-by-step explanation:
Baking soda contains the functional group known as the bicarbonate group. While carboxylic acids contain a carboxyl group, and this group features a carbon-oxygen double bond (C=O) called the carbonyl group, with the same carbon also being bonded to a hydroxyl (-OH) group, this is not the group present in baking soda. Instead, baking soda, which is sodium bicarbonate (NaHCO3), has a bicarbonate ion (HCO3-) functional group.