Final answer:
To find the theoretical oxygen demand of urea, the moles of urea are calculated and then used to determine the moles of oxygen required for complete combustion based on the balanced chemical equation. The moles of oxygen are then converted to mass, resulting in the theoretical oxygen demand.
Step-by-step explanation:
The theoretical oxygen demand of urea can be calculated using stoichiometry principles. Urea, with the chemical formula CO(NH₂)₂, requires oxygen for complete combustion. The balanced chemical equation for the combustion of urea is:
CO(NH₂)₂ + 3O₂ → CO₂ + 2H₂O + 2N₂
This equation shows that 1 mole of urea requires 3 moles of oxygen for complete combustion. To calculate the theoretical oxygen demand, we first need to calculate the number of moles of urea. Since the molar mass of urea is 60.06 g/mol, 5.00 g of urea is equivalent to 5.00 g / 60.06 g/mol = 0.0832 moles of urea. Following the stoichiometry, the oxygen demand is 0.0832 moles urea × 3 moles O₂/mole urea = 0.2496 moles O₂. To convert this to mass, we multiply by the molar mass of O₂, which is 32.00 g/mol, resulting in a theoretical oxygen demand of 0.2496 moles × 32.00 g/mol = 7.9872 g O₂.