At 300 K and 1 atmospheric pressure, 10 mL of a hydrocarbon required 55 mL of $\mathrm{O}_{2}$ for complete combustion, and 40 mL of $\mathrm{CO}_{2}$ is formed. The formula of the hydrocarbon is:

(B) $\mathrm{C}_{4} \mathrm{H}_{6}$

(A) $\mathrm{C}_{4} \mathrm{H}_{10}$

(C) $\mathrm{C}_{4} \mathrm{H}_{7} \mathrm{Cl}$

(D) $\mathrm{C}_{4} \mathrm{H}_{8}$

JEE Main · 2019 · 10 Apr 2019 · Shift 1 · Some Basic Concepts of Chemistry

At 300 K and 1 atmospheric pressure, 10 mL of a hydrocarbon required 55 mL of

O_{2}

for complete combustion, and 40 mL of

CO_{2}

is formed. The formula of the hydrocarbon is:

Answer: (B)

Apply the law of combining volumes at constant temperature and pressure. Burning

10

mL of

C X_{x} H X_{y}

yields

40

mL of

CO X_{2}

, so each molecule carries

4

carbons and

x = 4

. The oxygen balance for

C X_{x} H X_{y} + (x + \frac{y}{4}) O X_{2}

requires

10 (4 + \frac{y}{4}) = 55

, hence

4 + \frac{y}{4} = 5.5

and

y = 6

. The hydrocarbon is

C X_{4} H X_{6}

JEE Main · 2019 · 10 Apr 2019 · Shift 1 · Single correct option