Question

The production capacity for acrylonitrile (C₃H₃N) in the United States exceeds 2 million pounds per year. Acrylonitrile, the building block for polyacrylonitrile fibers and a variety of plastics, is produced from gaseous propylene, ammonia, and oxygen.

2 C₃H₆(g) + 2 NH₃(g) + 3 O₂(g) → 2 C₃H₃N(g) + 6 H₂O(g)

(a) What mass of acrylonitrile can be produced from a mixture of 1.22 kg of propylene (C₃H₆), 1.62 kg of ammonia, and 1.87 kg of oxygen, assuming 100% yield?

Answer 1

Given reaction

2 C₃H₆(g) + 2 NH₃(g) + 3 O₂(g) → 2 C₃H₃N(g) + 6 H₂O(g)

calculation of mass of acrylonitrile:

given : Mass of propylene = 1.22 kg = 1.22 E3 g

mass of ammonia = 1.62 kg = 1.62 E 3 g

mass of Oxygen = 1.87 E 3 g

First step is to determination of limiting reactant:

Limiting reactant is determined by calculation of moles of product from each of the reactants.

The reagent which gives less number of moles of product that would be limiting reactant and the moles of the product that are formed from limiting reactant are the maximum and we then calculate the mass of it by using molar mass.

Determination of limiting reactant.

We use following formula and mol ratio.

Moles = mass in g / molar mass.

Mole ratio between propylene and acrylonitrile is 2 : 2

Ammonia : acrylonitrile is 2 : 2

Oxygen : acrylonitrile is 3 : 2

Moles of acrylonitrile from propylene

Moles of acrylonitrile = ( 1.22 E 3 g / 42.0804 g per mol) x 2 mol acrylonitrile / 2 moles propylene

= 28.99 mol

From ammonia

Moles of acrylonitrile = ( 1.62 E 3 g / 17.0307 g per mol) x 2 mol acrylonitrile / 2 mol NH3

= 95.12 mol

From oxygen

Moles of acrylonitrile = ( 1.87 E 3 g / 31.998 g per mol ) x 2 mol acrylonitrile / 3 moles of oxygen

= 38.96 mol

We can see that moles of acrylonitrile from moles of propylene are less so propylene is limiting reactant and so the maximum moles of acrylonitrile that can be produced in this reaction = 28.99 mol

Calculation of mass of acrylonitrile

Mass of acrylonitrile = moles x molar mass

= 28.99 mol x 53.0637 g /mol

= 1538.43 g

And mass of acrylonitrile in kg = 1.538 kg