To calculate the percent yield of a chemical reaction, you need to compare the actual yield (what you collected) to the theoretical yield (what you expected to collect based on stoichiometry).
In this case, you collected 4.18 grams of aluminum chloride. To calculate the theoretical yield, you need to know the balanced chemical equation for the reaction and the stoichiometry involved. Let's assume you're reacting aluminum with chlorine gas to produce aluminum chloride. The balanced equation is:
2 Al + 3 Cl₂ → 2 AlCl₃
This equation tells you that 2 moles of aluminum react with 3 moles of chlorine gas to produce 2 moles of aluminum chloride. Therefore, you need to calculate the theoretical yield based on the amount of aluminum used.
Calculate the molar mass of AlCl₃:
Al: 1 * 26.98 g/mol = 26.98 g/mol
Cl: 3 * 35.45 g/mol = 106.35 g/mol
AlCl₃: 26.98 g/mol + 106.35 g/mol = 133.33 g/mol
Calculate the moles of AlCl₃ from the 4.18 grams you collected:
Moles of AlCl₃ = 4.18 g / 133.33 g/mol ≈ 0.0314 moles
Now, using the stoichiometry from the balanced equation, calculate the theoretical yield of AlCl₃ based on the moles of aluminum used:
Moles of AlCl₃ (theoretical) = Moles of Al (0.0314 moles) * (2 moles AlCl₃ / 2 moles Al) = 0.0314 moles
Calculate the theoretical mass of AlCl₃:
Mass of AlCl₃ (theoretical) = Moles of AlCl₃ (theoretical) * Molar mass of AlCl₃
Mass of AlCl₃ (theoretical) = 0.0314 moles * 133.33 g/mol ≈ 4.18 grams
Now you have the theoretical yield, which is also approximately 4.18 grams. To find the percent yield, use the following formula:
Percent Yield
=
Actual Yield
Theoretical Yield
×
100
Percent Yield=
Theoretical Yield
Actual Yield
×100
Substitute the values:
Percent Yield
=
4.18
grams (actual yield)
4.18
grams (theoretical yield)
×
100
=
100
%
Percent Yield=
4.18 grams (theoretical yield)
4.18 grams (actual yield)
×100=100%
So, your percent yield is 100%. You collected the same amount as the theoretical yield, which is ideal in a chemical reaction.