1. Atomic Masses

* Carbon (C): 12.011 atomic mass units (amu)

* Oxygen (O): 15.9994 amu

2. Calculation

* CO₂ has one carbon atom and two oxygen atoms.

* Total mass = (1 x 12.011 amu) + (2 x 15.9994 amu)

* Total mass = 12.011 amu + 31.9988 amu

* Total mass = 44.0098 amu

Therefore, the mass of a carbon dioxide molecule is approximately 44.0098 atomic mass units.