Question

A gaseous hydrocarbon gives upon combustion 0.72g of warter and 3.08 g of CO2 the empirical formula of hydrocarbon is

Answer 1

hey there !

18 gram of H20 contains 2 gram of hydrogen

0.72 gram of H2O contains 0.8 gram of H

44 gram of CO2 contains 12 gram of C

C: H =   0.84/12  : 0.08/1 =  0.07 : 0.08 = 7/8

empirical formula is C7H8 

Answer 2

We know,

Hydrocarbon contains C and H. Let he formula be $C_xH_y$
 
And

18 g of H₂O consist of 2 moles of H atoms.
Then, 0.72 g of H₂O consist of:
2/18 x 0.72 = 0.08

So, 0.72 g of H₂O consist of 0.08 moles of H atoms.

We know,

44 g of CO₂ consist of 1 mole of C atom.
Then, 3.08 g of CO₂ consist of:
1/44 x 3.08 = 0.07 

So, 3.08 g of CO₂ consist of 0.07 mole of C atom.

Then, ratio of x and y :
= 0.07/0.08 
= 7 : 8

So, empirical formula is $C_7H_8$