Question

Urea (CH4N2O) is a common fertilizer that can be synthesized by the reaction of ammonia (NH3) with carbon dioxide as follows: 2NH3(aq)+CO2(aq)→CH4N2O(aq)+H2O(l) In an industrial synthesis of urea, a chemist combines 132.0 kg of ammonia with 211.4 kg of carbon dioxide and obtains 172.7 kg of urea. determine the limiting reactant

Answer 1

Answer:

NH₃ is the limiting reagent

Explanation:

Mass of ammonia = 132.0kg

Mass of carbon dioxide = 211.4kg

Mass of urea = 172.7kg

Unknown:

Limiting reagent = ?

Solution

 First, we write the balanced stoichiometeric equation:

     2NH₃ + CO₂ → CH₄N₂O + H₂O

The reactant that is present in short supply determines the amount of product that is formed in a reaction. This reactant is called the limiting reagent.

    To establish the limiting reagent, we need to go find out what is happening at the start of the reaction:

Convert the masses of the reactants to moles.

Number of moles of NH₃ = $\frac{mass}{molar mass}$

   Molar mass of NH₃ = 14 + (3x1) = 17g/mol

   Number of moles of NH₃ =  $\frac{132}{17}$ = 7.765mole

Number of moles of CO₂ =  $\frac{mass}{molar mass}$

    Molar mass of CO₂ = 12 + (2 x 16) = 44g/mol

     Number of moles of CO₂ =  $\frac{211.4}{44}$ = 4.805mole

From the reaction equation:

   2 moles of NH₃ reacted with 1 mole of CO₂

so 7.765 mole of NH₃ will require $\frac{7.765}{2}$mole, 3.883 of CO₂

But we are given 4.805mole of CO₂.

Therefore, CO₂ gas is in excess and NH₃ is the limiting reagent.