Urea (NH2)2CO is prepared by reacting ammonia with carbon dioxide. The byproduct is water.

637.2g of ammonia are reacted with 787.3 g of carbon dioxide.
a. Which of the two reactants is a limiting reactant? Show your calculations (including the correctly
balanced chemical equation) to explain your choice.

what is the Balanced Chemical Equation:

Calculations:

Explanation and conclusion:

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

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

1a. mols NH3 = grams/molar mass
1b. mols CO2 = grams/molar mass

2a. Using the coefficients in the balanced equation, convert mols NH3 to mols of urea.
2b. Do the same to convert mols CO2 to mols urea.
2c. It is likely that these two values will not agree which means one of them is not right; the correct value in limiting reagent problems is ALWAYS the smaller value and the reagent producing that value is the limiting reagent.

3. Convert mols urea to grams urea by g urea = mols urea x molar mass urea. This is the theoretical yield.

a. The balanced chemical equation for the reaction between ammonia and carbon dioxide to form urea is:

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

To determine which reactant is the limiting reactant, we need to compare the moles of each reactant. First, we need to convert the given masses of ammonia (637.2g) and carbon dioxide (787.3g) to moles.

The molar mass of ammonia (NH3) is 17.03 g/mol, and the molar mass of carbon dioxide (CO2) is 44.01 g/mol.

For ammonia:
Moles of NH3 = mass of NH3 / molar mass of NH3
Moles of NH3 = 637.2g / 17.03 g/mol
Moles of NH3 ≈ 37.44 mol

For carbon dioxide:
Moles of CO2 = mass of CO2 / molar mass of CO2
Moles of CO2 = 787.3g / 44.01 g/mol
Moles of CO2 ≈ 17.86 mol

From the balanced chemical equation, the stoichiometry indicates that 2 moles of ammonia react with 1 mole of carbon dioxide to produce 1 mole of urea. Therefore, the ratio of moles of ammonia to carbon dioxide required for the reaction is 2:1.

Since the moles of ammonia (37.44 mol) are much greater than the moles of carbon dioxide (17.86 mol), ammonia is in excess, and carbon dioxide is the limiting reactant.

b. We should use the limiting reactant (carbon dioxide) to calculate the theoretical yield because it determines the maximum amount of product that can be formed. Theoretical yield is the amount of product that would be obtained if all of the limiting reactant is completely converted to the product based on the stoichiometry of the balanced equation.

a. The balanced chemical equation for the reaction between ammonia (NH3) and carbon dioxide (CO2) to form urea is:

2 NH3 + CO2 → (NH2)2CO + H2O

To determine the limiting reactant, we need to compare the number of moles of each reactant to the stoichiometry of the balanced equation.

First, we convert the masses of ammonia and carbon dioxide to moles using their molar masses. The molar mass of NH3 is approximately 17.03 g/mol, and the molar mass of CO2 is approximately 44.01 g/mol.

Number of moles of NH3 = 637.2 g / 17.03 g/mol ≈ 37.47 mol
Number of moles of CO2 = 787.3 g / 44.01 g/mol ≈ 17.86 mol

From the balanced chemical equation, we can see that 2 moles of NH3 react with 1 mole of CO2 to form 1 mole of (NH2)2CO. Therefore, the ratio of NH3 to CO2 is 2:1.

Ratio of NH3 to CO2 = 37.47 mol / 17.86 mol ≈ 2.10

Since the ratio is greater than 2, NH3 is in excess, and CO2 is the limiting reactant. CO2 determines the maximum amount of urea that can be formed.

b. The limiting reactant should be used to calculate the theoretical yield because it determines the maximum amount of product that can be formed. In this case, CO2 is the limiting reactant. By using its stoichiometry in the balanced equation, we can calculate the maximum amount of urea (theoretical yield) that can be obtained from the reaction.

Good