Question

A reactor is supplied with 5 moles each of CH3OH and O2, and the following reactions occur, CH3OH + 1/2O2 -> CH2O + H2O and then CH2O + 1/2O2 -> CO + H2O, the conversion of methanol is 80% in first reaction, and conversion of CH2O is 50% in second reaction. How many moles of O2 are there in the products?

(a) 1.75

(b) 2

(c) 3.25

(d) 5.5

This question was posed to me in an international level competition.

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

Answer 1

Correct choice is (a) 1.75

The best explanation: Extent of reaction E1 = (-0.8)/(-1) = 0.8, E2 = (-0.5)/(-1) = 0.5, => moles of O2 = (2.5 – 2.5*0.8) + (2.5 – 2.5*0.5) = 1.75.