The mass of an oxygen–18 atom is 18.0042 amu. Compute the calculated mass.

The calculated mass of one atom of oxygen-18  is approximately  2.99×10⁻²³ grams

Explanation:

The given mass of an oxygen-18 atom = 18.0042 amu

The definition of the atomic mass unit is the mass equivalent to the mass of one twelfth the atomic mass of one atom of carbon-12. The atomic mass unit is used to express the mass of an isotope of an element

1 amu = 1.66 × 10⁻²⁴ grams

Therefore;

18.0042 amu = 18.0042 ×  1.66 × 10⁻²⁴ grams ≈ 2.99×10⁻²³ grams

The calculated mass of one atom of oxygen-18 ≈ 2.99×10⁻²³ grams

The atomic mass unit can be taken as the mass in grams of one mole of the substance

Therefore, the mass of one mole of the oxygen 18 atom = 18.0042 g