JEE MAIN - Chemistry (2002 - No. 53)

In a compound C, H and N atoms are present in 9 : 1 : 3.5 by weight . Molecular weight of the compound is 108 g mol-1 . Molecular formula of compound is
C2H6N2
C3H4N
C6H8N2
C9H12N3

Explanation

Element Weight ratio No of atoms of element Simplest Ratio
C 9 9/12 = 3/4 3
H 1 1/1 = 1 4
N 3.5 3.5/14 = 1/4 1

Empherical Formula of the compound (EF) will be C3H4N

Now to find molecular formula at first find number of moles of given mass

No. of moles (n) =
Given mass
Molar mass


$$ \Rightarrow $$ $${{108} \over {54}}$$

$$ \Rightarrow $$ 2

$$\therefore$$ No. of Moles is 2

Molecular formula (MF) = n (no. of moles) $$\times$$ Empherical Formula (EF)

$$ \Rightarrow $$ 2 $$\times$$ C3H4N

$$ \Rightarrow $$ C6H8N2

$$\therefore$$ Option (C) is correct

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