Aspirin is a monoprotic acid called acetylsalicylic acid. Its formula is HC9H7O4. A certain pain reliever was analyzed for aspirin by dissolving 0.311 g of it in water and titrating it with 0.0398 M KOH solution. The titration required 22.32 mL of base. What is the percentage by weight of aspirin in the drug?

mols KOH = M x L = ?

mols aspirin = the same since both are monoprotic
g aspirin = mols x molar mass
%aspirin = (g aspirin/mass sample)*100 = ?

To find the percentage by weight of aspirin in the drug, we need to calculate the number of moles of aspirin and the mass of aspirin in the drug.

Step 1: Calculate the number of moles of KOH used in the titration.
We know the volume of KOH solution used is 22.32 mL, which is equal to 0.02232 L. The molarity of KOH solution is 0.0398 M.
moles of KOH = volume of KOH solution (L) × molarity of KOH
moles of KOH = 0.02232 L × 0.0398 M

Step 2: Calculate the moles of aspirin reacted in the titration.
From the balanced chemical equation, we know that 1 mole of KOH reacts with 1 mole of aspirin.
moles of aspirin = moles of KOH

Step 3: Calculate the mass of aspirin in the drug.
We are given the mass of the pain reliever as 0.311 g.
mass of aspirin = mass of pain reliever

Step 4: Calculate the percentage by weight of aspirin in the drug.
percentage by weight = (mass of aspirin / mass of pain reliever) × 100

Let's plug in the numbers to calculate the percentage by weight of aspirin in the drug:

Step 1: moles of KOH = 0.02232 L × 0.0398 M = 0.000886176 moles

Step 2: moles of aspirin = 0.000886176 moles

Step 3: mass of aspirin = 0.311 g

Step 4: percentage by weight = (0.000886176 moles / 0.311 g) × 100 = 0.2847%

Therefore, the percentage by weight of aspirin in the drug is approximately 0.2847%.

To find the percentage by weight of aspirin in the drug, we need to determine the number of moles of aspirin and the mass of the drug.

1. Determine the moles of KOH used in the titration:
- Molarity of KOH solution = 0.0398 M
- Volume of KOH used = 22.32 mL = 0.02232 L
- Moles of KOH = molarity × volume = 0.0398 mol/L × 0.02232 L = 0.00088536 mol

2. Determine the moles of aspirin used in the titration:
- From the balanced chemical equation between KOH and aspirin, we know that 1 mole of KOH reacts with 1 mole of aspirin.
- Therefore, the number of moles of aspirin is also 0.00088536 mol.

3. Determine the mass of the drug:
- Mass of aspirin = moles × molar mass
- Molar mass of aspirin (HC9H7O4) = (1.01 g/mol × 9) + (12.01 g/mol × 9) + (16.00 g/mol × 4) = 180.16 g/mol
- Mass of aspirin = 0.00088536 mol × 180.16 g/mol = 0.1594 g

4. Calculate the percentage by weight of aspirin in the drug:
- Percentage by weight = (Mass of aspirin / Mass of drug) × 100%
- Percentage by weight = (0.1594 g / 0.311 g) × 100% = 51.2%

Therefore, the percentage by weight of aspirin in the drug is approximately 51.2%.