What is HCHO commonly known as? 

Formaldehyde 

The correct answer is option 2. Formaldehyde.

Formaldehyde, with the chemical formula HCHO, is a colorless, strong-smelling gas that is highly soluble in water. It is the simplest aldehyde and is commonly encountered in various industrial, commercial, and household applications. Here's an explanation of formaldehyde:

1. Chemical Structure: Formaldehyde consists of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydrogen atom (H-C=O). It is the simplest member of the aldehyde family, characterized by the presence of the carbonyl functional group (-CHO).

2. Occurrence: Formaldehyde is naturally produced by certain metabolic processes in plants and animals. It is also found in trace amounts in some foods and beverages. Additionally, formaldehyde is widely used in industry for the production of resins, plastics, and other organic chemicals.

3. Properties: Formaldehyde is a highly reactive compound that readily undergoes polymerization and other chemical reactions. It has a pungent odor and is a potent irritant to the eyes, nose, throat, and respiratory system. Formaldehyde gas can also cause skin irritation upon contact.

4. Uses: Formaldehyde has numerous industrial applications due to its ability to crosslink and polymerize with other molecules. It is commonly used in the production of urea-formaldehyde resins, phenol-formaldehyde resins, and melamine-formaldehyde resins, which are used in the manufacture of plywood, particleboard, and other wood products. Formaldehyde is also used as a disinfectant, preservative, and embalming agent. In the medical field, formaldehyde solutions are used to preserve biological specimens.

5. Health Effects: Formaldehyde is classified as a carcinogen by several health organizations, including the International Agency for Research on Cancer (IARC). Prolonged or repeated exposure to formaldehyde vapor can increase the risk of respiratory problems, allergic reactions, and certain types of cancer, particularly leukemia.

In summary, formaldehyde is a versatile chemical compound with widespread industrial applications. While it plays a vital role in various manufacturing processes, precautions should be taken to minimize exposure to formaldehyde vapor due to its potential health risks.