Question

Hydrogen gas is a very useful reagent with many uses in the petroleum, food, and chemical industries. Most hydrogen exists in covalently bonded molecules, and atmospheric air contains less than 1 ppm of diatomic hydrogen. Therefore, hydrogen gas is produced on a large scale for these uses, where steam reforming with methane and electrolysis of water are two of the primary methods. The more economic reaction of steam reforming is the reverse of the reaction depicted in Carbon Monoxide and Hydrogen - Sample 1 in the Simulation. Hydrogen has also been considered as an alternative fuel for vehicles designed to combust hydrogen and oxygen, which produces water as a product. However, concerns were raised because methane is typically used on a large scale to produce hydrogen gas. Assume that a gallon of gasoline contains 2400 g of carbon. If a gasoline engine achieves 30 miles per gallon, each mile consumes 80 g of carbon (about 107 g of methane contains 80 g of carbon). Alternatively, a hydrogen engine can achieve 80 miles per kilogram of hydrogen gas. What is the mass of methane (CH4) needed to produce enough hydrogen gas (H2) to drive one mile using the theoretical hydrogen engine? Express the mass in grams to two significant digits.

Answer 1

From the given data,

80 miles of engine is driven from 1 kg of H2 or 1000 g. of H2

then, 1 mile can be driven from 1000 / 80 = 12.5 g. of H2

So, theoretically to drive 1 mile of it needs 12.5 g. of H2 gas.

Prodcution of H2 from methane can be writeen as,

CH4 + H2O -------------> CO + 3 H2

From the above balanced equaiton,

1 mol of CH4 produces 3 mol H2

(OR)

16 g. of CH4 produces 6 g. of H2

Then,

12.5 g. of H2 can be produced from 12.5 * 16 / 6 = 33. g. of Methane.