1. **Stating the problem:** Calculate the relative molecular mass of carbon dioxide (CO₂) using the given atomic masses. 2. **Formula:** The relative molecular mass (M_r) of a compound is the sum of the relative atomic masses of all atoms in its formula. 3. **Given data:** - Carbon (C) atomic mass = 12 - Oxygen (O) atomic mass = 16 4. **Molecular formula of CO₂:** 1 carbon atom and 2 oxygen atoms. 5. **Calculation:** $$M_r = (1 \times 12) + (2 \times 16) = 12 + 32 = 44$$ 6. **Explanation:** We multiply the atomic mass of each element by the number of atoms of that element in the molecule, then add all these values to get the total molecular mass. 7. **Final answer:** The relative molecular mass of CO₂ is **44**.