Question

Urea (NH₂)₂CO is prepared by reactign ammonia with carbon dioxide. The byproduct is water. 637.2g of ammonia are reacted with 787.3g of carbon dioxide.

A) write a balanced equation

B) Determine which of the reactants (ammonia or carbon dioxide) is a limiting reactant. Show calculations to support your choice

C) Which of the two reactants should you use to calculate the theoretical yield (=the maximum amount possible) of urea. Explain why

Answer 1

Urea (NH₂)₂CO is prepared by reactign ammonia with carbon dioxide. The byproduct is water. 637.2g of ammonia are reacted with 787.3g of carbon dioxide.

      A) write a balanced equation

Solution :-   Balanced reaction equation is as follows

               2NH3 + CO2 -------> (NH2)2CO + H2O

B) Determine which of the reactants (ammonia or carbon dioxide) is a limiting reactant. Show calculations to support your choice

Solution :- Les calculate the moles of each reactant

Moles = mass / molar mass

Moles of NH3 = 637.2 g / 17.03 g per mol = 37.42 mol NH3

Moles of CO2 = 787.3 g /44.01 g per mol = 17.889 mol CO2

Now lets calculate the moles of the NH3 needed to react with the 17.889 mol CO2 using the mole ratio of the NH3 and CO2

Mole ratio is 2 mol NH3 = 1 mol CO2

Therefore

17.889 mol CO2 * 2 mol NH3 / 1 mol CO2 = 35.8 mol NH3

Moles of NH3 needed for the reaction are less than moles of the NH3 available

Therefore NH3 is the excess reagent and CO2 is the limiting reactant.

Limiting reactant = CO2

C) Which of the two reactants should you use to calculate the theoretical yield (=the maximum amount possible) of urea. Explain why

Solution :-

We always use the limiting reactant to calculate the theoretical yield of the reaction, because the limiting reactant is the reactant which run out first during the reaction therefore no further product formed.

Hence we always have to use the mole ratio of the limiting reactant and product to calculate the theoretical yield of the reaction.