Q.

The elemental composition of a compound is 54.2% C, 9.2% H and 36.6% O. 

If the molar mass of the compound is 132 g mol-1 the molecular formula of the compound is: 

[Given : The relative atomic mass of C : H : O = 12 : 1 : 16]                       [2025]

1 C6H12O3  
2 C4H8O2  
3 C4H9O3  
4 C6H12O6  

Ans.

(1)

Element Mass % Number of moles of atom in 100 g compound = Mass% / molar mass of atom Relative number Simple ratio
C 54.2 54.2 / 12 = 4.517 4.517 / 2.2875 = 1.97 2
H 9.2 9.2 / 1 = 9.2 9.2 / 2.2875 = 4.02 4
O 36.6 36.6 / 16 = 2.2875 2.2875 / 2.2875 = 1 1

 

Empirical formula=C2H4O

Empirical formula mass=(2×12+4×1+16) g=44 g

n=Molecular formula massEmpirical formula mass=13244=3

Molecular formula=(Empirical formula)n=(C2H4O)3=C6H12O3