The reaction of methane and water is one way to prepare hydrogen: CH_4(g) + H_2O (g) -> CO (g) + 3H_2(g) [Molar masses 16.04 18.02 28.01 2.02]. If you begin with 995 g of CH_4 and 2510 g of water, what is the maximum possible yield of H_2?

1 Answer
Aug 1, 2017

Methane is the limiting reactant, therefore the maximum possible yield of hydrogen gas is 376 g.

Explanation:

Balanced Equation

"CH"_4("g") + "H"_2"O(g)"rarr"CO(g)" + "3H"_2("g")"

This is a limiting reactant stoichiometry problem. We will determine whether methane or water is the limiting reactant. The limiting reactant will give us the maximum possible yield of hydrogen gas.

color(blue)("Maximum Yield of") color(blue)("H"_2" color(blue)("Produced by" color(blue)("995 g CH"_4

Determine the moles "CH"_4 in "995 g CH"_4 by dividing the given mass by its molar mass by multiplying by the inverse of the molar mass.

995color(red)cancel(color(black)("g CH"_4))xx(1"mol CH"_4)/(16.04color(red)cancel(color(black)("g CH"_4)))="62.0 mol CH"_4

Multiply the moles "CH"_4 by the mole ratio between "H"_2 and "CH"_4, "3 mol H"_2:"1 mol CH"_4.

62.0color(red)cancel(color(black)("mol CH"_4))xx(3"mol H"_2)/(1color(red)cancel(color(black)("mol CH"_4)))="186 mol H"_2"

color(teal)"Maximum Yield of" color(teal)("H"_2) color(teal)("produced by" color(teal)(2510"g H"_2"O"

Determine the moles "H"_2"O" by dividing the given mass by its molar mass by multiplying by the inverse of the molar mass.

2510color(red)cancel(color(black)("g H"_2"O"))xx(1"mol H"_2"O")/(18.02color(red)cancel(color(black)("g H"_2"O")))="139 mol H"_2"O"

Multiply the moles "H"_2"O" by the mole ratio between "H"_2 and "H"_2"O", "3 mole H"_2:1"mol H"_2"O".

139color(red)cancel(color(black)("mol H"_2"O"))xx(3"mol H"_2)/(1color(red)cancel(color(black)("mol H"_2"O")))="417 mol H"_2"

The limiting reactant is "CH"_4 since it produced the least number of moles of "H"_2. In order to determine the mass "H"_2" that is possible, multiply the moles "H"_2 by the molar mass of "H"_2.

color(magenta)("Maximum Possible Yield of H"_2"

186color(red)cancel(color(black)("mol H"_2))xx(2.02"g H"_2)/(1color(red)cancel(color(black)("mol H"_2)))="376 g H"_2" (rounded to three sig figs)