Question

A gas mixture has 10% CH4 with pressure 5 Pa at 27^oC at the rate F, is passed through a reactor with another stream containing 60% CH4 with pressure 5 Pa at -73^oC at the rate 10 liter/s, if the percentage of CH4 with pressure 5 Pa at 27^oC in product is 80%, what is the value of F?

(a) 1 liter/s

(b) 1.4 liter/s

(c) 2 liter/s

(d) 2.6 liter/s

This question was posed to me in a job interview.

This key question is from Material Balances Involving Ideal Gases in section Recycle, Bypass, Purge, Ideal Gases and Real Gases of Basic Chemical Engineering

Answer 1

The correct choice is (b) 1.4 liter/s

Explanation: Overall material balance: F + 10 = P, Overall CH4 Balance: 0.1*F*5/300 + 0.6*10*5/200 = 0.8*P*5/300, => F + 90 = 8P, => F = 10/7 = 1.4 liter/s.