Question

10 moles of ethane is supplied with 49 moles of oxygen, what is the percentage of excess oxygen?

(a) 20%

(b) 40%

(c) 50%

(d) 70%

This question was addressed to me by my college professor while I was bunking the class.

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

Answer 1

Correct option is (b) 40%

For explanation I would say: The balanced reaction is C2H6 + 3.5O2 -> 2CO2 + 3H2O, => O2 required = 3.5*10 = 35 moles, => percentage of excess oxygen = 100*(49 – 35)/35 = 40%.