Calculate the formula unit masses of `ZnO , Na_(2) O , K_(2) CO_(3)` , given atomic masses of Zn = 65 u , Na = 23 u , K = 39 u , C = 12 u , and O = 16 u

Explanation

(i) Atomic mass of O = 16 u
Formula unit mass of ZnO
= At.mass of Zn + At.mass of O
= 65 + 16
= 81 u
(ii) Atomic mass of Na = 23 u
Atomic mass of O = 16 u
Formula unit mass of `Na_(2)O`
= 2 `xx` At.mass of Na + At.mass of O
`= 2 xx 23 + 16`
`= 46 + 16`
= 62 u
(iii) Atomic mass of K = 39 u
Atomic mass of C = 12 u
Atomic mass of O = 16 u
Formula unit mass of `K_(2) CO_(3)`
`= 2 xx` At. mass of K + At . mass of C + 3 `xx` At. mass of O
`= 2 xx 39 + 12 + 3 xx 16`
`= 78 + 12 + 48`
= 138 u