Question

Which of the following compound(s) has /have percentage of carbon same as that in ethylene (C2H4)
(a) propene
(b) ethyne
(c) benzene
(d) ethane

Answer 1

Answer ⇒ Option (a) is correct. Propene. 

Solutions ⇒ 
Molar mass of the Ethylene = 12 × 2 + 1 × 4
= 24 + 4
= 28 g/mole.

Mass of the Carbon Present in Ethylene = 12 × 2 
= 24

∴ % composition of the Carbon = 24/28 × 100
  = 85.71 %

(a) Molar mass of the Propene(C₃H₆) = 12 × 3 + 1 × 6
 = 36 + 6
 = 42 g/mole.

Mass of the Carbon present in the Propene = 36 g.

∴ % composition of C = 36/42 ×100
 = 85.71 %

(b) Molar mass of the Ethyne (C₂H₂) = 12 × 2 + 1 × 2
 = 24 + 2
 = 26 g.

Mass of the Carbon Present in Ethyne = 12 × 2 
 = 24 g.

% compo. of C = 24/26 × 100
 = 92.31 %

(c). Molar mass of the Benzene (C₆H₆) = 12 × 6 + 1 × 6
 = 72 + 6
 = 78 g.

Mass of the C present in Benzene = 12 × 6 
 = 72 g

% comp.  = 72/78 × 100
 = 92.31 %

(d). Molecular Mass of the Ethane (C₂H₆) = 12 × 2 + 1 × 6
 = 24 + 6
 = 30 g

Mass of the C present in Ethane = 12 × 2
 = 24 g.

% comp. of the C = 24/30 × 100
= 80 %

From these Calculations we can see that the % composition of the C of the Ethylene is same as that of the Propene. 
Hence Propene is correct.


Hope it helps.

Answer 2

The correct answer is propene