Vinegar is an aqueous solution of?

Step 1: Analyze the question The question asks which acid is the main component of vinegar, the common household liquid used in cooking and food preservation.

Step 2: Explain the concept Vinegar is made by the fermentation of ethanol (from sugary or starchy materials). Bacteria called Acetobacter oxidize the ethanol to ethanoic acid, which is also called acetic acid.

• Ethanol → Ethanoic acid (by oxidation)
• CH₃CH₂OH + O₂ → CH₃COOH + H₂O

Household vinegar is usually about 4-8% ethanoic acid dissolved in water.

Step 3: Check each option

• A. Hydrochloric acid (HCl): A strong mineral acid found in the stomach (gastric juice) and used in laboratories. It is not in vinegar.
• B. Ethanedioic acid (oxalic acid, (COOH)₂): Found in some plants, such as spinach and sorrel. It is toxic in large amounts and is not vinegar.
• C. Ethanoic acid (CH₃COOH): This is the acid in vinegar. ✔
• D. Hydrofluoric acid (HF): A very corrosive acid used to etch glass. It is definitely not in food.

Step 4: Answer Vinegar is an aqueous solution of ethanoic acid, which is option C.

Tip: Link the words: vinegar = acetic = ethanoic. Also remember that "eth-" means 2 carbons, and "-oic acid" means a carboxylic acid (-COOH). The name "ethanedioic" has "di" for two -COOH groups, which is oxalic acid, so don't confuse the two in the exam!