Question

Methane is at the rate 50 moles is supplied to a reactor with air at the rate 1000 moles, the reactor leaves O2, N2, CO2 and H2O, what is the percentage of H2O in products?

(a) 5.8%

(b) 9.5%

(c) 15.4%

(d) 20.7%

This question was addressed to me in an internship interview.

My question is taken from Material Balances Involving Combustion in section The Chemical Reaction Equation & Stoichometry, Material Balances for Processes Involving Reaction and Multiple Units of Basic Chemical Engineering

Answer 1

Right choice is (b) 9.5%

The explanation is: The reaction is CH4 + 2O2 -> CO2 + 2H2O. O2 supplied = 1000*21/100 = 210 moles, N2 supplied = 1000*79/100 = 790 moles, => Osub>2 unreacted = 210 – 100 = 110 moles, COsub>2 formed = 50 moles, Hsub>2O formed = 100 moles. => Percentage of H2O = 100/1050*100 = 9.5%.