Question

Assuming that petrol is octane $(C_8H_{18})$ and has density $0. 8 \,g/ml, \,1.425$ litre of petrol on complete combustion will consume

• A. $50$ mole of $O_2$
• B. $125$ mole of $O_2$
• C. $100$ mole of $O_2$
• D. $200$ mole of $O_2$

Answer 1

Answer: (B)

Mass of octane $= 1.425 \times 103 \times 0.8\, g$
Moles of octane $= \frac{1425\times .8}{114} = 10$ moles
$C_8H_{18} + \frac{25}{2} O_2 \to 8CO_2 + 9H_2O$
From the equation it can be seen
For $1$ mole octane oxygen required $\frac{25}{2}$ moles
$\therefore $ for $1$ moles octane oxygen required
$\frac{25}{2} \times 10 = 125$ moles