Q14 / 90 · JEE Main 2023 (31 Jan Shift 2) · Chemistry

When a hydrocarbon $A$ undergoes complete combustion it requires $11$ equivalents of oxygen and produces $4$ equivalents of water. What is the molecular formula of $A$ ?

Solution

By using the formula of combustion analysis:

$C_{x} H_{y} + (x + \frac{y}{4}) O_{2} \to {CO}_{2} + \frac{y}{2} H_{2} O$

Given, $(x + \frac{y}{4}) a = 11 a$

$x + \frac{y}{4} = 11$

$(\frac{y}{2}) a = 4 a$

$y = 8$ ,

then $x + \frac{8}{4} = 11$

$x = 11 - \frac{8}{4}$

$x = 9$

Formula $= C_{9} H_{8}$

Hence, the correct answer is option: 'D'.