A gaseous compound is composed of 85.7 % by mass carbon and 14.3 % by mass hydrogen. Its density is 2.28 g / litre at 300 K and 1.0 atm pressure. Determine the molecular formula of the compound.

Question

A gaseous compound is composed of 85.7 % by mass carbon and 14.3 % by mass hydrogen. Its density is 2.28 g / litre at 300 K and 1.0 atm pressure. Determine the molecular formula of the compound. (A) C 2 H 2 (B) C 2 H 4 (C) C 4 H 8 (D) C 4 H 10

Tardigrade Admin · Accepted Answer

d=(P M/R T) ⇒ M=(d R T/P)=(2.28 × 0.0821 × 300/1) =56.15 g / mol Atomic ratio =(85.7/12): (14.3/1)=7.14: 14.3=1: 2; ∴ E.F is CH 2 ; M.F. =( CH 2) n where n=(56.15/12+2) ≃ 4 ; ∴ M.F. is C 4 H 8

Q. A gaseous compound is composed of $85.7%$ by mass carbon and $14.3%$ by mass hydrogen. Its density is $2.28$ $g /$ litre at $300 K$ and $1.0 a t m$ pressure. Determine the molecular formula of the compound.

$C_{2} H_{2}$

$C_{2} H_{4}$

$C_{4} H_{8}$

$C_{4} H_{10}$

$d = \frac{PM}{RT} \Rightarrow M = \frac{d RT}{P} = \frac{2.28 \times 0.0821 \times 300}{1}$
$= 56.15 g / m o l$
Atomic ratio $= \frac{85.7}{12} : \frac{14.3}{1} = 7.14 : 14.3 = 1 : 2$ ;
$∴$ E.F is $C H_{2};$ M.F. $= (C H_{2}) n$
where $n = \frac{56.15}{12 + 2} ≃ 4;$
$∴$ M.F. is $C_{4} H_{8}$

Q. A gaseous compound is composed of 85.7% by mass carbon and 14.3% by mass hydrogen. Its density is 2.28 g/ litre at 300K and 1.0atm pressure. Determine the molecular formula of the compound.

C2​H2​

C2​H4​

C4​H8​

C4​H10​