Question

write the meaning of formula unit mass .Calculate the formula unit mass of compound Na2S2O3

Answer 1

It is the sum of the atomic masses of all the atoms present in the formula unit of that compound. It is calculated in the same manner as that of molecular mass. The only difference is that we use formula unit mass for those substances whose constituent particles are ions.

FORMULA UNIT MASS OF Na2S2O3:-

= 2*(at. mass of Na) + 2*(at. mass of S) + 3*(At. mass of oxygen)

= 2*23 + 2*32 + 3*16

=158u

Answer 2

formula unit mass is the sum of the atomic masses of all atoms present in formula unit of a compound it is calculated by adding atomic masses of all the atoms present in one formula unit

formula unit mass of Na2S2O3

=2×atomic mass of Na + 2×atomic mass of S + 3 × atomic mass of O

=2×23+2×32+3×16

=46+64+48

=158u