Fuel cells have been proposed for use in cars and for power generation as part of a hydrogen economy. They offer the advan-tages of higher efficiency (not limited by heat cycle efficiencies) and cleaner fuel with no significant pollutants. The net reaction is as follows:

2H ₂ + O ₂ → 2H ₂ 0

Where O ₂ comes from the air (which, for this problem, can be assumed to be 21 mole% O ₂ and 79 mole% N ₂ ). Hydrogen (112) flows into a fuel cell implemented in a prototype vehicle at a rate of 27 gmollmin. Air (consisting of oxygen and nitrogen) enters the fuel cell in a separate stream. The amount of oxy-gen entering the fuel cell is 50% more than that needed to react stoichiometrically with all of the entering hydrogen. The con-version of hydrogen in the fuel cell is 85%. Assume that only a single stream exits the fuel cell. What is the flow rate of each of the species leaving the fuel cell? Note that the flow rates given correspond to a fuel cell rated at approximately 50 kW using 2004 technology.

Answer rating: 100% (QA)

The reaction in question is 2H 2 O2 2H 2 O So the reaction uses 2 moles of hydrogen and 1 mole of O ... View the full answer