What is HCOOH commonly known as? 

Formic acid 

The correct answer is option 4. Formic acid.

Formic acid, with the chemical formula \(HCOOH\), is a colorless, pungent-smelling liquid. It is the simplest carboxylic acid and occurs naturally in various plants and animal venom, such as ants. Here's a brief explanation:

1. Chemical Structure:  Formic acid consists of a carboxyl group (-COOH), which is a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group (-OH). The other carbon atom in formic acid is attached to a hydrogen atom.

2. Occurrence:  Formic acid is found in nature, primarily in the venom of certain insects, particularly ants. It is also present in the stings of bees and the secretions of some caterpillars. Additionally, formic acid can be produced synthetically through various chemical processes.

3. Properties: Formic acid is highly soluble in water and has a pungent odor. It is considered a weak acid, meaning it does not completely dissociate in water. However, it can still corrode certain metals and cause burns upon contact with the skin.

4. Uses: Formic acid has several industrial applications. It is used as a preservative and antibacterial agent in animal feed and silage. It is also used in the production of leather, textiles, and rubber. In addition, formic acid is utilized in various chemical processes, such as the synthesis of other organic compounds.

5. Health Effects: Concentrated formic acid can be corrosive and toxic if ingested or inhaled. Exposure to formic acid vapors can irritate the respiratory system and eyes. However, dilute solutions of formic acid are generally safe when handled properly.

In summary, formic acid is a versatile compound with both natural and industrial applications. Its presence in nature and its chemical properties make it a valuable substance in various contexts