If you use 1 gram of salacylic acid and 3ml of acetic anhydride & 3 drops of phosphoric acid and 1 ml of water after boiling = 0.55 g of aspirin. What is the % yield?
You must first determine which is the limiting reagent; i.e., salicylic acid or acetic anhydride. And you need the density of acetic anhydride to do that.
mols salicylic acid = grams/molar mass = ?
mols acetic anhydride = grams/molar mass. grams you get by grams = volume x density.
Convert mols S.A. to mols of the product.
Do the same for acetic anhydride.
It is likely you will obtain two different answers; the correct one in limiting reagent problems is ALWAYS the smaller one and the reagent producing that number is the limiting reagent.
mols product x molar mass = grams. This is the theoretical yield (T. E.)
%yield = (actual yield/T. E.)*100 = ?
To calculate the percent yield, you need two values: the actual yield and the theoretical yield.
The actual yield is the amount of product obtained from the reaction, which in this case is 0.55g of aspirin.
The theoretical yield is the maximum amount of product that can be obtained based on stoichiometry and assuming 100% conversion of reactants. To determine the theoretical yield of aspirin, you need the balanced chemical equation for the reaction involved. The balanced equation for the synthesis of aspirin from salicylic acid is:
C7H6O3 + C4H6O3 -> C9H8O4 + C2H4O2.
From this equation, you can see that 1 mole of salicylic acid (C7H6O3) reacts with 1 mole of acetic anhydride (C4H6O3) to produce 1 mole of aspirin (C9H8O4). Therefore, the molar ratio between salicylic acid and aspirin is 1:1.
Now you can calculate the theoretical yield using the given mass of salicylic acid. The molar mass of salicylic acid (C7H6O3) is approximately 138 g/mol.
1 g of salicylic acid * (1 mol / 138 g) = 0.0072 mol of salicylic acid.
Since the molar ratio between salicylic acid and aspirin is 1:1, the theoretical yield of aspirin is also 0.0072 mol.
To convert the theoretical yield from moles to grams, use the molar mass of aspirin (C9H8O4) which is approximately 180 g/mol:
0.0072 mol * (180 g / 1 mol) = 1.29 g of aspirin.
Now that you have both the actual yield (0.55 g) and the theoretical yield (1.29 g), you can calculate the percent yield using the formula:
% yield = (actual yield / theoretical yield) * 100.
% yield = (0.55 g / 1.29 g) * 100 = 42.6%.
Therefore, the percent yield of the reaction is approximately 42.6%.