Question

Octane is burnt with 40% excess O2, what is the percentage of CO2 in products?

(a) 18.18%

(b) 36.36%

(c) 54.54%

(d) 72.72%

I got this question in an interview for job.

I would like to ask this question from Material Balances Involving Combustion topic in portion The Chemical Reaction Equation & Stoichometry, Material Balances for Processes Involving Reaction and Multiple Units of Basic Chemical Engineering

Answer 1

Correct choice is (b) 36.36%

The best I can explain: The reaction is C8H18 + 12.5O2 -> 8CO2 + 9H2O. Basis: 10 moles of C8H18, => moles of O2 reacted = 125, => moles of O2 entered the process = 175, => moles of CO2, H2O and O2 in products are 80, 90 and 50, => percentage of CO2 = 80/220*100 = 36.36%.