Question

H2 at 27^oC with pressure 10 atm and volume 10 liter is passed through a reactor with 6 moles of oxygen, if the limiting reagent reacts completely, how many moles of oxygen is left unreacted?

(a) 1

(b) 2

(c) 4

(d) 6

I got this question during an internship interview.

Enquiry is from Material Balances Involving Ideal Gases topic in chapter Recycle, Bypass, Purge, Ideal Gases and Real Gases of Basic Chemical Engineering

Answer 1

Correct choice is (c) 4

Explanation: The reaction is 2H2 + O2 -> 2H2O, moles of H2 passed = 10*10/(0.0821*300) = 4, => moles of H2 reacted = 4, => moles of O2 reacted = 4, => moles of O2 left unreacted = 6 – 2 = 4.