Which of the following is not a volatile organic compound?

Acetaldehyde
Formaldehyde
Hydrochloric Acid
Dichloromethan

The correct answer is (c), Hydrochloric Acid.

A volatile organic compound (VOC) is a chemical compound that has a high vapor pressure at ordinary temperatures. VOCs are often found in gasoline, paint, and other household products. When VOCs are released into the air, they can contribute to ground-level ozone formation and smog.

Acetaldehyde (CH3CHO) is a colorless, flammable liquid with a characteristic, pungent odor. It is used in the production of plastics, resins, and other chemicals. Formaldehyde (CH2O) is a colorless, flammable gas with a pungent odor. It is used in the production of plastics, resins, and other chemicals. Dichloromethane (CH2Cl2) is a colorless, flammable liquid with a sweetish odor. It is used as a solvent and in the production of refrigerants and other chemicals.

Hydrochloric acid (HCl) is a colorless, fuming liquid with a strong, sour odor. It is used in the production of chemicals, pharmaceuticals, and other products. Hydrochloric acid is not a VOC because it does not have a high vapor pressure at ordinary temperatures.