Question

Calculate the formula masses of the following compounds.

(a) Sodium oxide, Na₂O

(b) Aluminium oxide, Al₂O₃

Answer 1

Recall the atomic mass values required,

Na = 23u, O = 16u, Al = 27u

To derive the values,

(a) Formula masses for Sodium oxide, Na₂O

= (2 x Atomic mass of Na) + (Atomic mass of O)

= (2 x 23) + (16) = 46 + 16

= 62u

(b) Formula masses for Aluminium oxide, Al₂O₃

= (2 x Atomic mass of Al) + (Atomic mass of O)

= (2 x 27) + (3 x 16) = 54 + 48

= 102u

From the above, the formula masses for the compounds are,

(a) Sodium oxide, Na₂O = 62u

(b) Aluminium oxide, Al₂O₃ = 102u