In the synthesis of asprin we react salicylic acid (HOOCC6H4OH) with acetic anhydride (C4H6O3) . The unbalanced chemical equation is:
HOOCC6H4OH + C4H6O3 --> HOOCC6H4O2C2H3 + H2O
If we mix together 28.2 g of salicylic acids with 15.6 g of acetic anhydride in this reaction we obtain 30.7 grams of asprin. What is the percent yield for this reaction?
To calculate the percent yield for this reaction, we first need to determine the theoretical yield, which is the amount of asprin that would be obtained if the reaction went to completion.
To do this, we need to convert the given masses of salicylic acid and acetic anhydride to moles using their respective molar masses.
The molar mass of salicylic acid (HOOCC6H4OH) is calculated as follows:
(1 H * 1.0079 g/mol) + (1 O * 15.999 g/mol) + (3 C * 12.011 g/mol) + (6 H * 1.0079 g/mol) + (1 C * 12.011 g/mol) + (1 O * 15.999 g/mol) + (1 O * 15.999 g/mol) + (1 H * 1.0079 g/mol) = 138.122 g/mol
The molar mass of acetic anhydride (C4H6O3) is calculated as follows:
(4 C * 12.011 g/mol) + (6 H * 1.0079 g/mol) + (3 O * 15.999 g/mol) = 102.089 g/mol
Next, we need to determine the limiting reactant, which is the reactant that is completely consumed in the reaction and determines the maximum amount of product that can be formed.
To determine the limiting reactant, we calculate the number of moles of each reactant using the given masses and their respective molar masses:
Moles of salicylic acid = 28.2 g / 138.122 g/mol
Moles of acetic anhydride = 15.6 g / 102.089 g/mol
Next, we need to compare the ratio of moles of each reactant to the stoichiometric coefficients in the balanced equation. The balanced equation shows that the ratio of moles of salicylic acid to moles of acetic anhydride is 1:1.
In this case, we can see that the moles of salicylic acid and acetic anhydride are equal, indicating that they are present in the stoichiometric ratio specified by the balanced equation. Therefore, neither salicylic acid nor acetic anhydride is in excess, and they will react completely.
Now, we can calculate the theoretical yield of asprin using the stoichiometry of the balanced equation:
The molar mass of asprin (HOOCC6H4O2C2H3) is calculated as follows:
(1 H * 1.0079 g/mol) + (1 O * 15.999 g/mol) + (3 C * 12.011 g/mol) + (6 H * 1.0079 g/mol) + (4 C * 12.011 g/mol) + (2 O * 15.999 g/mol) + (2 H * 1.0079 g/mol) + (3 C * 12.011 g/mol) + (4 H * 1.0079 g/mol) = 180.158 g/mol
The number of moles of asprin formed is the same as the number of moles of salicylic acid or acetic anhydride, which we calculated above.
Moles of asprin = 28.2 g / 138.122 g/mol
Now, we can calculate the theoretical yield of asprin by multiplying the number of moles of asprin by its molar mass:
Theoretical yield of asprin = Moles of asprin * molar mass of asprin
Finally, we can calculate the percent yield by dividing the actual yield (30.7 g) by the theoretical yield and multiplying by 100:
Percent yield = (Actual yield / Theoretical yield) * 100
Substituting the given values:
Percent yield = (30.7 g / Theoretical yield) * 100
Therefore, to calculate the percent yield, we need to first determine the theoretical yield using the method described above, and then divide the actual yield by the theoretical yield and multiply by 100.