Organic Chemistry Basics Result Question 16
16. A gaseous hydrocarbon gives upon combustion $0.72 \mathrm{~g}$ of water and $3.08 \mathrm{~g}$ of $\mathrm{CO} _2$. The empirical formula of the hydrocarbon is
(2013 Main)
(a) $\mathrm{C} _2 \mathrm{H} _4$
(b) $\mathrm{C} _3 \mathrm{H} _4$
(c) $\mathrm{C} _6 \mathrm{H} _5$
(d) $\mathrm{C} _7 \mathrm{H} _8$
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Answer:
Correct Answer: 16. ( d )
Solution:
$\begin{aligned} & 18 \mathrm{~g} \mathrm{H}_2 \mathrm{O} \text { contains } 2 \mathrm{~g} \mathrm{H} \\ & \therefore 0.72 \mathrm{~g} \mathrm{H}_2 \mathrm{O} \text { contains } 0.08 \mathrm{~g} \mathrm{H} \\ & 44 \mathrm{~g} \mathrm{CO}_2 \text { contains } 12 \mathrm{~g} \mathrm{C} \\ & \therefore 3.08 \mathrm{~g} \mathrm{CO}_2 \text { contains } 0.84 \mathrm{~g} \mathrm{C} \\ & \therefore \quad \mathrm{C}: \mathrm{H}=\frac{0.84}{12}: \frac{0.08}{1} \\ & =0.07: 0.08=7: 8 \\ & \therefore \text { Empirical formula }=\mathrm{C}_7 \mathrm{H}_8 \\ & \end{aligned}$
BETA
