Question

2.0 g of carbon has reacted with hydrogen gas that would take the volume of 4.48 L at STP .

            C + 2H₂ ===> CH₄

What is the % yield of this reaction if 1.4 g of CH₄ has been produced?

Answer 1

C + 2H₂ ===> CH₄

As per the stoichiometry of reaction

One mole of carbon (12 grams) will react with 2 moles of Hydrogen (2 X 2 gram) to give one mole of methane (16 grams)

The carbon used = 2 grams

Moles of carbon = Mass / Atomic weight of carbon = 2/12 = 0.167 moles

Moles of hydrogen gas required wil lbe calcualted as

The actual yield will be calcualted using ideal gas equation

PV = nRT

Pressure = 1 atm

Volume = 4.48 L

Temperature = 273.15 K

R = 0.0821 Latm / Mol K

moles = PV / RT = 1 X 4.48 / 298.15 X 0.0821 = 0.183 moles

So here the limiting reagent is hydrogen gas .

0.183 moles of H2 will react with = 0.183/2 moles of carbon = 0.0915 moles of carbon to give 0.0915 moles of methane

Theoretical yield = Moles of methane x mol wt = 0.0915 X 16 = 1.464 grams

Mass of methane produced = 1.4 grams

% yield = actual yield X 100 / theoretical yield = 1.4 X 100 / 1.464 = 95.62%