Question

define the formula unit mass of a compound. calculate the formula unit mass of(a) Na2Co2,10H2O (b)CuSo4.(given atomic mass of Na-23u,C-12u,Cu-63.5u,S-32u)

Answer 1

formula unit mass of a substance or compound is the sum of the atomic masses of all atoms in a formula unit of a compound. The term formula unit is used for those substances which are made up of ions. The formula unit mass of Na2Co3.10H2O(=Atomic mass of Na + Atomic mass of carbon + atomic mass of Oxygen + 10 Atomic mass of Hydrogen + Atomic mass of Oxygen, 2 into 23 + 12 + 3 into 16+ 10 into 2 into atomic hydrogen + Atomic mass of oxygen(2+16), 46+12+48+10 into 18=286u, (b) CuSo4= the atomic mass of Cu + the atomic mass of sulphur + 4 into atomic mass of oxygen= 63.5+32+4 (16)=159.5u

Answer 2

(a) (Na2Co3)

2×23+12×1+16×3+10(1×2+16×1)

46+12+48+180

=286u

(b) (CuSo4)

63.38+1×32+16×4

63.38+32+64

=159.38