Question

One mole of an alkane on complete combustion required 8 mole of $O_2$, find out sum of carbon and hydrogen atoms in one molecule of the alkane.

Answer 1

This problem is based on the general combustion reaction of alkanes. Alkanes follow the general formula $C_n H_{2n+2}$.
1. General reaction for combustion:
$C_n H_{2n+2} + \left(\frac{3n+1}{2}\right)O_2 \rightarrow nCO_2 + (n+1)H_2O$

2. Stoichiometry:
From the reaction, 1 mole of alkane requires $\frac{3n+1}{2}$ moles of $O_2$.
According to the question, moles of $O_2$ required = 8.

3. Equate and solve for n:
$\frac{3n+1}{2} = 8$
$3n + 1 = 16$
$3n = 15$
$n = 5$

4. Identify the alkane:
Since $n=5$, the alkane is Pentane ($C_5H_{12}$).

5. Calculate sum of atoms:
Number of Carbon atoms = 5
Number of Hydrogen atoms = 12
Total atoms = $5 + 12 = 17$.