Ammonia , NH₃ , dissociates into hydrogen and oxygen gases , according to the following equation :

2 NH₃ --> 3 H₂ + N₂

A student was asked to determine how many moles of hydrogen gas, H₂ , would be produced from 7.5 moles of NH₃ . The student set up his calculation correctly as :

(7.5 mol NH3) x [conversion factor ] = # mol of H2 .

What was the conversion factor used in this calculation ?

a. Conversion factor = [ ( 3 mol H₂ ) / ( 2 mol NH₃ ) ]
b. Conversion factor = [ ( 2 mol NH₃ ) / ( 3 mol H₂ ) ]
c. Conversion factor = [ ( 3 mol H₂ ) / ( 1 mol N₂ ) ]
d. Conversion factor = [ ( 2 mol NH₃ ) / ( 1 mol N₂ ) ]