Question

If an alkane contains 'n' number of carbon atoms, the numbers of oxygen molecules required for combustion of alkane are

• A. $\frac{2n+1}{2}$
• B. 2n+1
• C. $\frac{3n+1}{2}$
• D. n

Answer 1

Answer: (C)

$\frac{3n+1}{2}$

Answer 2

For an alkane $C_nH_{2n+2}$, the balanced combustion reaction is:

$$C_nH_{2n+2} + \frac{3n+1}{2} O_2 \rightarrow nCO_2 + (n+1)H_2O$$

Thus, the number of $\text{O}_2$ molecules required is $\frac{3n+1}{2}$.

Balanced the combustion equation to get $\frac{3n+1}{2}$ molecules of $\text{O}_2$.