Question

Calculate the formula unit mass of Na₂CO₃. [Atomic mass of Na = 23 u, C = 12 u, O = 16 u]

Answer 1

The formula unit mass of a substance is the sum of the atomic masses of all the atoms in the formula unit of an ionic compound. 

Therefore, formula unit mass of Na₂CO₃ 

= 2Na + 1C + 3O = (2 × 23) + (1 × 12) +( 3 × 16) = 46 + 12 + 48 = 106 u.