a. The percentage yield of SiO₂ for Trial 1 is approximately 93.31%
The leftover reactants are 10.8892 g of SiCl₄ and 173.794944 g of O₂
b. The ratio of the reactants, SiCl₄ to O₂, in Trial 2 of 3:2 is more efficient than that of Trial 1, which is 3:4
Explanation:
a. The chemical reaction can be expressed as follows;
SiCl₄ (g) + O₂ (g) → SiO₂ (s) + 2Cl₂ (g)
Therefore, for the theoretical yield, we have;
1 mole of SiCl₄ combines with 1 mole of O₂ to yield 1 mole of SiO₂ and 2 moles of Cl₂
The molar mass of SiCl₄ = 169.9 g/mol
The molar mass of O₂ ≈ 32 g/mol
The molar mass of SiO₂ (s) = 60.08 g/mol
The number of moles of SiCl₄ present in 150 g of SiCl₄ = 150 g/(169.9 g/mol) ≈ 0.883 moles
The number of moles of O₂ present in 200 g of O₂ = 200 g/(32 g/mol) ≈ 6.25 moles
The number of moles of SiO₂ present in 49.2 g of SiCl₄ = 49.2 g/(60.08 g/mol) ≈ 0.818908 moles
Therefore, the theoretical yield of SiO₂ from 0.883 moles of SiCl₄ is 0.883 moles of SiO₂
The mass of 0.833 moles of SiO₂ = 0.833 moles × 60.08 g/mol = 50.04664 grams
The percentage yield = Actual yield/(Theoretical yield) × 100
∴ The percentage yield of SiO₂ for Trial 1 = 49.2 g/(50.04664 g) × 100 ≈ 93.31%
The percentage yield of SiO₂ for Trial 1 ≈ 93.31%
The left over reactant are given as follows;
The number of moles of SiO₂ produced = 0.818908 moles = The number of moles of SiCl₄ used
∴ The number of moles of SiCl₄ remaining = (The number of moles of SiCl₄ present) - (The number of moles of SiCl₄ used)
The number of moles of SiCl₄ remaining = 0.883 moles - 0.818908 moles = 0.064092 moles
The mass of the SiCl₄ remaining = 0.064092 moles × 169.9 g/mol ≈ 10.8892 g
The mass of the SiCl₄ remaining ≈ 10.8892 g
The number of moles of O₂ remaining = (The number of moles of O₂ present) - (The number of moles of O₂ used)
The number of moles of O₂ used in the reaction = The number of moles of SiO₂ produced = 0.818908 moles
∴ The number of moles of O₂ remaining = 6.25 moles - 0.818908 moles = 5.431092 moles
The mass of O₂ remaining = 32 g/mol × 5.431092 moles = 173.794944 grams
The leftover reactants are 10.8892 g of SiCl₄ and 173.794944 g of O₂
b. For trial 2, we have;
The number of moles of SiCl₄ present in 75 g of SiCl₄ = 75 g/(169.9 g/mol) ≈ 0.441436139 moles
The number of moles of O₂ present in 50 g of O₂ = 50 g/(32 g/mol) ≈ 1.5625 moles
The number of moles of SiO₂ present in 25.2 g of SiCl₄ = 25.2 g/(60.08 g/mol) ≈ 0.419440746 moles
Therefore, the theoretical yield of SiO₂ from 0.441436139 moles of SiCl₄ is 0.441436139 moles of SiO₂
The mass of 0.441436139 moles of SiO₂ = 0.441436139 moles × 60.08 g/mol = 26.5214832 grams
The percentage yield of SiO₂ for Trial 2 = 25.2 g/(26.5214832 g) × 100 ≈ 95.02%
Therefore, the ratio of reactants in Trial 2 which is of the ratio SiCl₄ to O₂ of 3:2 is more efficient than that of 3:4 of Trial 1.