Question

A gaseous hydrocarbon gives upon combustion 0.72 g of water and 3.08 g. of CO₂. The empirical formula of the hydrocarbon is :
(a) C₂H₄
(b) C₃H₄
(c) C₆H₅
(d) C₇H₈

Answer 1

Hey there!

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 C₇H₈.

Hope It Helps You!