A gaseous hydrocarbon gives upon combustion 0.72 g of water and 3.08 g of $\mathrm{CO}_{2}$. The empirical formula of the hydrocarbon is:

(C) $\mathrm{C}_{7} \mathrm{H}_{8}$

(A) $\mathrm{C}_{3} \mathrm{H}_{4}$

(B) $\mathrm{C}_{6} \mathrm{H}_{5}$

(D) $\mathrm{C}_{2} \mathrm{H}_{4}$

JEE Main · 2013 · 07 Apr 2013 · Offline · Some Basic Concepts of Chemistry

A gaseous hydrocarbon gives upon combustion 0.72 g of water and 3.08 g of

CO_{2}

. The empirical formula of the hydrocarbon is:

Answer: (C)

Read the carbon and hydrogen back from the combustion products. The

3.08 g

CO X_{2}

\frac{3.08}{44} = 0.07 mol

, carrying

0.07 mol

of carbon, while the

0.72 g

of water is

\frac{0.72}{18} = 0.04 mol

, carrying

0.08 mol

of hydrogen. The ratio

C : H = 0.07 : 0.08 = 7 : 8

, so the empirical formula is

C X_{7} H X_{8}

JEE Main · 2013 · 07 Apr 2013 · Offline · Single correct option