Question

One mole of alkane reacts with 8 moles of \( O_2 \). The molecular formula of alkane is:

• A. \( C_{10}H_{22} \)
• B. \( C_3H_{12} \)
• C. \( C_7H_{14} \)
• D. \( C_3H_8 \)

Hint:

In combustion reactions, the stoichiometry of oxygen can be used to determine the molecular formula of the alkane.

Answer 1

The Correct Option is D

The general combustion reaction of an alkane is: \[ C_xH_y + O_2 \rightarrow CO_2 + H_2O \] For the complete combustion of one mole of alkane, the stoichiometry of oxygen required is determined by balancing the equation. From the reaction: \[ C_xH_y + \left(x + \frac{y}{2}\right) O_2 \rightarrow xCO_2 + \frac{y}{2} H_2O \] Since one mole of alkane reacts with 8 moles of \( O_2 \), we equate \( x + \frac{y}{2} = 8 \). Solving for \( x \) and \( y \), the molecular formula of the alkane is \( C_3H_8 \). Final Answer:} \( C_3H_8 \).