Compound A contains 8.7% Hydrogen, 74% Carbon and 17.3% Nitrogen. The molecular formula of the compound is,
Given : Atomic masses of C, H and N are 12, 1 and 14 amu respectively.
The molar mass of the compound A is 162 g mol$-$1.
Solution
<p>Mole ratio of H, C and N</p>
<p>$= {{8.7} \over 1}:{{74} \over {12}}:{{17.\,3} \over {14}}$</p>
<p>$= 8\,.7:6.167:1.23$</p>
<p>$= {{8.7} \over {1.23}}:{{6.167} \over {1.23}}:{{1.23} \over {1.23}}$</p>
<p>$= 7:5:1$</p>
<p>$\therefore$ Emperical formula = ${{C_5}{H_7}N}$</p>
<p>$\therefore$ Molecular formula $= {\left( {{C_5}{H_7}N} \right)_n}$</p>
<p>Given molecular mass = 162</p>
<p>Molecular mass of ${\left( {{C_5}{H_7}N} \right)_n}$</p>
<p>$= (5 \times 12 + 7 \times 1 + 14) \times n$</p>
<p>$= (81) \times n$</p>
<p>$\therefore$ $81 \times n = 162$</p>
<p>$\Rightarrow n = 2$</p>
<p>$\therefore$ Molecular formula = C<sub>10</sub>H<sub>14</sub>N<sub>2</sub></p>
About this question
Subject: Chemistry · Chapter: Some Basic Concepts of Chemistry · Topic: Mole Concept
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