what is the theoretical yield in grams of aspirin if 2.04g of salicycli acid reacts with an excess of acetic anhydride ?

Here is a worked example of a stoichiometry problem. Just follow the steps.

http://www.jiskha.com/science/chemistry/stoichiometry.html

To find the theoretical yield of aspirin, we need to know the balanced chemical equation for the reaction between salicylic acid and acetic anhydride. The equation is as follows:

C7H6O3 + (C2H3O)2O → C9H8O4 + CH3COOH

From the balanced equation, we can see that 1 mole of salicylic acid (C7H6O3) reacts with 1 mole of acetic anhydride ((C2H3O)2O) to produce 1 mole of aspirin (C9H8O4) and 1 mole of acetic acid (CH3COOH).

To find the moles of salicylic acid, we divide the given mass by its molar mass. The molar mass of salicylic acid is calculated as follows:

Molar mass (salicylic acid) = 7(12.01 g/mol) + 6(1.008 g/mol) + 3(16.00 g/mol)
= 138.12 g/mol

Given mass of salicylic acid = 2.04 g

Moles of salicylic acid = 2.04 g / 138.12 g/mol

Now, since salicylic acid is in excess, it will be the limiting reagent while acetic anhydride is in excess. Therefore, the number of moles of aspirin produced will be equal to the number of moles of salicylic acid used.

Now, we can calculate the moles of aspirin produced. Since the molar ratio of salicylic acid to aspirin is 1:1 (from the balanced equation), the moles of aspirin will also be 2.04 g / 138.12 g/mol.

Finally, to calculate the theoretical yield of aspirin in grams, we multiply the moles of aspirin produced by its molar mass:

Theoretical yield (aspirin) = Moles of aspirin × Molar mass (aspirin)

Remember to use the correct molar mass for aspirin in your calculation.