Aspirin synthesis and Analysis:

Calculate theoretical yield of ASA?
Used 3.5mL of acetic anhydride and 1.5g of salicylic acid.

This is a limiting reagent problem and you don't have enough information to work the problem. You have 3.5 mL acetic anhydride and you need to convert that to mols. You need the density of the acetic anhydride to convert 3.5 mL to grams.

Here is a site that will show you how to solve limiting reagent problems.
http://www.jiskha.com/science/chemistry/limiting_reagent_problem.html

To calculate the theoretical yield of acetylsalicylic acid (ASA), you need to follow these steps:

1. Determine the balanced chemical equation for the reaction. The synthesis of ASA from salicylic acid and acetic anhydride can be represented as follows:

C7H6O3 + (CH3CO)2O → C9H8O4 + CH3COOH

2. Calculate the molar mass of each compound involved in the reaction:
- Molar mass of salicylic acid (C7H6O3) = 138.12 g/mol
- Molar mass of acetic anhydride ((CH3CO)2O) = 102.09 g/mol
- Molar mass of acetylsalicylic acid (ASA) (C9H8O4) = 180.16 g/mol

3. Convert the given quantities into moles:
- Moles of salicylic acid = mass of salicylic acid / molar mass of salicylic acid
- Moles of salicylic acid = 1.5 g / 138.12 g/mol

4. Determine the limiting reagent. To do this, compare the moles of each reactant with their stoichiometric coefficients in the balanced equation. The reactant with fewer moles compared to the stoichiometric coefficient is the limiting reagent. In this case, we need to compare the moles of salicylic acid and acetic anhydride.

5. Calculate the moles of acetyl salicylic acid formed by using the stoichiometry of the balanced equation:
- It can be inferred from the balanced equation that 1 mole of salicylic acid reacts with 1 mole of acetic anhydride to produce 1 mole of acetylsalicylic acid.

6. Calculate the theoretical yield of acetyl salicylic acid using the following formula:
- Theoretical yield (g) = theoretical yield (moles) × molar mass of ASA

Now, let's calculate the theoretical yield of ASA using the given information:

Moles of salicylic acid = 1.5 g / 138.12 g/mol ≈ 0.010860 mol

Since 1 mole of salicylic acid reacts with 1 mole of acetic anhydride, the moles of acetic anhydride used would also be 0.010860 mol.

Theoretical yield (moles) = 0.010860 mol

Theoretical yield (g) = theoretical yield (moles) × molar mass of ASA
= 0.010860 mol × 180.16 g/mol
≈ 1.96 g

Therefore, the theoretical yield of acetylsalicylic acid (ASA) is approximately 1.96 grams.