Question

The industrially important chemical, urea [CH4N2O; molar mass = 60.0 grams per mole], is prepared from the reaction of ammonia [NH3: molar mass = 17.0 grams per mole] with carbon dioxide [CO2; molar mass = 44.0 grams per mole] according to the following: 2 NH3 + CO2  CH4N2O + H2O If one reacts 132.0 grams of CO2 with 136.0 grams of ammonia, which of these would be the limiting reagent?

Answer 1

Molar mass of NH3 = 17.0 g/mol

mass(NH3)= 136.0 g

use:

number of mol of NH3,

n = mass of NH3/molar mass of NH3

=(136 g)/(17.03 g/mol)

= 7.984 mol

Molar mass of CO2 = 44.0 g/mol

mass(CO2)= 132.0 g

use:

number of mol of CO2,

n = mass of CO2/molar mass of CO2

=(132 g)/(44.0 g/mol)

= 3.00 mol

Balanced chemical equation is:

2 NH3 + CO2 ---> CH4N2O + H2O

2 mol of NH3 reacts with 1 mol of CO2

for 7.984 mol of NH3, 3.992 mol of CO2 is required

But we have 3.0 mol of CO2

so, CO2 is limiting reagent

Answer: CO2