Question

A compound (molecular mass 64.59u) has the following data:
(table)
Elements A B C
Relative No. of atom 3.10 7.80 1.55
% Composition 37.215 7.8 54.98
Determine:
(i) Atomic masses of the elements A,B and C
(ii) Simplest atomic ratios of the elements
(iii) Molecular formula of the compound

Answer 1

Explanation:

Step I : Calculation of the atomic masses of the elements

Atomic mass of element =Percentage of elementRelative no. of atoms

Atomic mass of A=37.2153.10=12u

Atomic mass of B=7.87.8=1.0 u

Atomic mass of C=54.981.55=35.5 u

Step II. Calculation of simplest atomic ratios of the elements

ElementABCRelative no. of atoms3.107.81.55Simplest atomic ratio3.101.55=27.81.55=51.551.55=1

Step III. Calculation of the molecular formula

Empirical formula of compound =A2B5C

Empitical formula mass of the compound =2×12+5×1.0+35.5=64.5 u

n=Molecular massEmpirical formula mass=64.5964.5=1

∴ Molecular formula =1(A2B5C)=A2B5C.