Example of Hydrogen for Fuel Cells

As a specific example, consider the water-gas shift reaction that can be used in a chemical process to make hydrogen for fuel cell applications  

Thermodynamic data give the value of In K = 5 (or K = 148.4) at 500 K. If you start with a stoichiometric mixture of carbon monoxide and water, what will the equilibrium composition be In this case, the number of moles remains the same when the reaction takes place, and you are left with 

Step 1 To begin, make a mole balance table (see Table 4.1), with a basis of 1 mol each of carbon monoxide and water, which then react to equilibrium. Use x to represent the number of moles reacting, thus giving the values in the table. 

You can easily solve this equation by taking the square root, giving x = 0.924. In more complicated cases it would not be possible to solve it so easily. Instead, you would 

TABLE 4.1. Solution for Equilibrium of Water-Gas Shift Reaction 

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