Question

A gaseous hydrocarbon gives upon combustion, 0.72 g water and 3.08 g of the empirical formula of hydrocarbon is :

Answer 1

Answer:

0.72 gram of H2O will contain 0.8 gram of H

44 gram of CO2 will contain 12 gram of C

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

Hence, Empirical formula is C7H8

Answer 2

Question:

A gaseous hydrocarbon gives upon combustion 0.72 g of H2O and 3.08 g of CO2. The empirical formula of the hydrocarbon is

Solution:

We know,

Hydrocarbon contains C and H. Let he formula be  

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 C₇H₈.