Calculate the formula unit masses of ZnO, Na\( _2 \)O, K\( _2 \)CO\( _3 \), given atomic masses of Zn = 65u, Na = 23 u, K=39u, C = 12u, and O=16u.

Given, atomic masses of Zn = 65u, Na = 23u, K = 39u, C = 12u, O = 16u

We know that formula unit mass of a substance is the sum of the atomic masses of all the atoms in the formula unit of the substance.

So, the formula unit mass of ZnO  = Atomic mass of Zn + Atomic mass of O = 65 + 16 = 81u

The formula unit mass of Na\( _2 \)O  = 2 × Atomic mass of Na + Atomic mass of O = (2 × 23) +16 = 46 + 16 = 62u

The formula unit mass of K\( _2 \)CO\( _3 \)  = 2 × Atomic mass of K + Atomic mass of C + 3 × Atomic mass of O = (2 × 39) + 12 + (3 × 16) = 78 + 12 + 48 = 138u