Organic Chemistry Basics Result 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 ( $1 \mathrm{~mol}$ ) be $\mathrm{C} _x \mathrm{H} _y \mathrm{~N} _z$. In Dumas method,
$$ \begin{aligned} & \mathrm{C}_x \mathrm{H}_y \mathrm{~N}_z+\left(2 x+\frac{y}{2}\right) \mathrm{CuO} \rightarrow x \mathrm{CO}_2+\frac{y}{2} \mathrm{H}_2 \mathrm{O}+\frac{z}{2} \mathrm{~N}_2+\left(2 x+\frac{y}{2}\right) \mathrm{Cu} \\ \end{aligned} $$
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 $\mathrm{C}_6 \mathrm{H}_8 \mathrm{~N}_2$.
BETA
