Question

Propane is burnt with 20% excess O2, what is the percentage of CO2 in products?

(a) 12.5%

(b) 25%

(c) 45%

(d) 75.5%

This question was posed to me during an interview.

My doubt stems from Material Balances Involving Combustion in portion The Chemical Reaction Equation & Stoichometry, Material Balances for Processes Involving Reaction and Multiple Units of Basic Chemical Engineering

Answer 1

Correct option is (a) 12.5%

Explanation: The reaction is C3H8 + 5O2 -> 3CO2 + 4H2O. Basis: 10 moles of C3H8, => moles of O2 reacted = 50, => moles of O2 entered the process = 60, => moles of CO2, H2O and O2 in products are 30, 40 and 10, => percentage of CO2 = 10/80*100 = 12.5%.