A hydrocarbon contains a benzene ring. It is made up of 91.43% carbon and its molar mass is about 105g/mol. What is the molecular formula of this hydrocarbon?

1 Answer
Oct 31, 2016

The given hydrocarbon contains

#C->91.43% and H->8.57%#

Dividing the percentage composition of constituent elements with respective atomic mass and takig their ratio we get the ratio of number of atoms of Carbon and Hydrogen as

#N_C:N_H=91.43/12:8.57/1=7.62:8.57=1:8.57/7.62=1:1.125=8:9#

So empirical formula of the hydrcarbon is #C_8H_9#

Let its MF be #(C_8H_9)_n#

As per this formula its molar mass becomes #(8*12+9*1)n=105n" g/mol"#

Its molar has been given #105" g/mol"#

So #105n=105=>n=1#

Hence MF of the HC is #C_8H_9#