Thirty pounds of coal (analysis 80% C and 20% H ignoring the ash) are burned with 600 lbs of air (with a variable humidity), yielding a gas have an Orsat analysis in which the ratio of CO₂ to CO is 3 to 2. What is the percent excess air?

It is proposed to produce ethylene oxide ((CH₂)₂O) by the oxidation of ethane (C₂H₆) in the gas phase:

 C₂H₆ + O₂ --> (CH₂)₂O + H₂O

The ratio of the air to the ethane in the gross feed into the reactor is 10 to one, and conversion of ethane on one pass through the reactor is 18%. The unreacted ethane is separated from the reactor products and recycled in a gas recycle with purge. The products can be separated out. For 100 moles of ethane feed into the system, what is the ratio of the recycle stream to the feed stream, and what is the composition of the outlet gas from the reactor. Both answers should be functions of the purge fraction (use xp as the variable for the purge fraction).