The mass of 12 daltons of carbon-12 is exactly 12 grams. This is because the dalton (symbol: Da) and the unified atomic mass unit (u) are defined as the same unit of measurement. The unified atomic mass unit is defined as 1/12th the mass of a carbon-12 atom. Therefore, by definition, the mass of one carbon-12 atom is 12 atomic mass units (12 amu), which is equivalent to 12 daltons. Consequently, 12 daltons of carbon-12 is equivalent to 12 grams.