Identifying Acids in Common Substances

Different naturally occurring substances, especially fruits and foods, contain various organic acids. These acids contribute to the taste, preservation, and other characteristics of the substance. The question asks to identify the option where the substance and the acid present in it are NOT correctly matched.

Let's examine each option:

1. The acid present in tomato – Formic acid

   Tomatoes are acidic, but the primary acids found in them are citric acid and malic acid. Formic acid, also known as methanoic acid (\(\text{HCOOH}\)), is notably found in the venom of ant stings and bee stings, and in some plants like nettles. Therefore, matching tomato with formic acid is incorrect.

2. The acid present in orange – Citric acid

   Oranges are citrus fruits and are well-known for their high content of citric acid (\(\text{C}_6\text{H}_8\text{O}_7\)). Citric acid is a common organic acid found in many fruits, especially citrus fruits like lemons, limes, and oranges. This pairing is correct.

3. The acid present in grapes – Tartaric acid

   Grapes are a significant natural source of tartaric acid (\(\text{C}_4\text{H}_6\text{O}_6\)). Tartaric acid is one of the main acids in grapes and is important in winemaking. This pairing is correct.

4. The acid present in rancid butter – Butyric acid

   Butter primarily consists of fats. When butter goes rancid, a process called hydrolysis occurs, breaking down the fats into fatty acids, including butyric acid (\(\text{C}_4\text{H}_8\text{O}_2\)). Butyric acid is a short-chain fatty acid that gives rancid butter its characteristic unpleasant smell and taste. This pairing is correct.

Based on the analysis of each option, the only incorrect match is the one pairing tomato with formic acid.

Summary of Common Acids and Sources

The question asks for the option that is NOT the correct match. We determined that tomato contains citric and malic acid, not formic acid.

Conclusion on Acid Matching

Evaluating the given options, the pairing "The acid present in tomato – Formic acid" is incorrect because tomatoes contain primarily citric and malic acids, not formic acid.

Revision Table: Acids in Foods

Additional Information on Organic Acids

Organic acids are a large group of organic compounds that have acidic properties. They are commonly found in living organisms, including fruits, vegetables, and animal products. They often contain a carboxyl group (\(\text{-COOH}\)).

• Citric acid: A weak organic acid found in citrus fruits. Used as a natural preservative and flavouring agent.
• Tartaric acid: A white, crystalline organic acid found in grapes and some other fruits. Used in baking (as cream of tartar), as a food additive, and in winemaking.
• Butyric acid: A saturated fatty acid with the chemical formula \(\text{CH}_3\text{CH}_2\text{CH}_2\text{COOH}\). It is found in butter and is produced by bacteria in the gut. Its smell is unpleasant, especially when concentrated.
• Formic acid: The simplest carboxylic acid (\(\text{HCOOH}\)). It is an intermediate in chemical synthesis and occurs naturally in the venom of some insects (like ants) and the stinging hairs of nettles.
• Malic acid: An organic acid found in many fruits, including apples and tomatoes. It contributes to the sour taste.
• Lactic acid: Produced in muscles during anaerobic respiration and by bacteria during fermentation of milk (in yogurt, cheese).

Understanding the common acids found in different foods is helpful for chemistry and biology studies, as well as in cooking and food science.