Organic Chemistry Basics 2 Question 8
8. An organic compound is estimated through Dumas method and was found to evolved 6 moles of $\mathrm{CO}{2}, 4$ moles of $\mathrm{H}{2} \mathrm{O}$ and 1 mole of nitrogen gas. The formula of the compound is
(2019 Main, 11 Jan I)
(a) $\mathrm{C}{6} \mathrm{H}{8} \mathrm{~N}$
(b) $\mathrm{C}{12} \mathrm{H}{8} \mathrm{~N}$
(c) $\mathrm{C}{12} \mathrm{H}{8} \mathrm{~N}_{2}$
(d) $\mathrm{C}{6} \mathrm{H}{8} \mathrm{~N}_{2}$
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Answer:
Correct Answer: 8. (d)
Solution:
- In Dumas method, organic compound is heated with dry cupric oxide in a combustion tube in the atmosphere of $\mathrm{CO}{2}$. Upon heating, $\mathrm{C}$ and $\mathrm{H}$ present are oxidised to $\mathrm{CO}{2}$ and water vapours while $\mathrm{N}{2}$ is set free. Let, the molecular formula of the organic compound (1 mol) be $\mathrm{C}{x} \mathrm{H}{y} \mathrm{~N}{z}$. In Dumas method,
$x \mathrm{~mol} \quad \frac{y}{2} \mathrm{~mol} \quad \frac{z}{2} \mathrm{~mol}$
Now, $x=6, \frac{y}{2}=4 \Rightarrow y=8$ and $\frac{z}{2}=1 \Rightarrow z=2$
$\therefore$ Molecular formula of the compound is $\mathrm{C}{6} \mathrm{H}{8} \mathrm{~N}_{2}$.
