What is the chemical formula for water?

The chemical formula for water is H2O. This formula indicates that each molecule of water consists of two hydrogen atoms (represented by the "H2") and one oxygen atom (represented by the "O"). This specific combination is crucial because the unique arrangement of these atoms contributes to water’s many essential properties, such as its solvent abilities, surface tension, and high heat capacity.

The other options represent different substances: CO2 is the formula for carbon dioxide, H2SO4 is sulfuric acid, and NaCl is table salt. Each of these compounds has distinct chemical properties and functions that are unrelated to water.