What is the chemical formula for water?

The chemical formula for water is H2O, which indicates that each molecule of water is composed of two hydrogen atoms and one oxygen atom. This specific arrangement creates a polar molecule with unique properties, such as being a solvent for many substances and having a high heat capacity, which are essential for sustaining life. Understanding the composition of water is fundamental in chemistry, as it is not only integral to biological processes but also plays a crucial role in various chemical reactions and environmental systems. The other options represent entirely different compounds; for instance, CO2 is carbon dioxide, O2 is molecular oxygen, and NaCl is table salt, none of which relate to the composition of water.