3) A student dissolves a 1.18g aspirin tablet in water and titrates the
solution with a .265M NaOH. 22.05mL of NaOH are required to reach the
equivalence point. Calculate the percentage of acetylsalicylic acid in the tablet.
moles NaOH needed = M x L = ??
moles ASA = same as moles NaOH since this is a 1:1 titration. I assume you know the reaction.
grams ASA = moles ASA x molar mass ASA.
%ASA = (grams ASA/mass sample)*100 = ?
To calculate the percentage of acetylsalicylic acid in the tablet, we need to determine the number of moles of acetylsalicylic acid in the 1.18g tablet. Then, using the volume and concentration of NaOH used in the titration, we can find the number of moles of NaOH that reacted with the acetylsalicylic acid. From these values, we can calculate the percentage of acetylsalicylic acid in the tablet.
First, let's calculate the number of moles of acetylsalicylic acid in the tablet:
1. Determine the molar mass of acetylsalicylic acid (C9H8O4).
- Look up the atomic masses of carbon (C), hydrogen (H), and oxygen (O) from the periodic table.
- Multiply the atomic masses by the number of atoms in each element in the formula (9 carbons, 8 hydrogens, and 4 oxygens).
- Add up the results to get the molar mass of acetylsalicylic acid.
2. Use the formula: Moles = Mass / Molar Mass, where the mass is 1.18g and the molar mass is calculated in step 1.
Next, let's determine the number of moles of NaOH used in the titration:
1. Use the formula: Moles = Concentration x Volume, where the concentration is 0.265M (given) and the volume is 22.05mL.
Now that we have the number of moles of acetylsalicylic acid and NaOH, we can calculate the percentage of acetylsalicylic acid in the tablet:
1. Use the formula: Percentage = (Moles of Acetylsalicylic Acid / Moles of NaOH) x 100.
Plug in the values and calculate the percentage.
Remember to pay attention to the significant figures throughout the calculations and round the final answer to an appropriate number of decimal places.
To calculate the percentage of acetylsalicylic acid in the tablet, follow these steps:
Step 1: Determine the number of moles of NaOH used in the titration.
Given that the volume of NaOH used is 22.05 mL and the concentration of NaOH is 0.265 M, we can calculate the moles of NaOH using the formula:
moles NaOH = concentration of NaOH × volume of NaOH
moles NaOH = 0.265 M × (22.05 mL / 1000 mL/1 L)
moles NaOH = 0.00582525 moles
Step 2: Use the balanced chemical equation for the reaction between NaOH and acetylsalicylic acid (aspirin) to determine the mole ratio between NaOH and acetylsalicylic acid.
The balanced equation is:
C9H8O4 + NaOH → NaC9H7O4 + H2O
From the balanced equation, we can see that the mole ratio between NaOH and acetylsalicylic acid is 1:1.
Step 3: Calculate the number of moles of acetylsalicylic acid.
Since the mole ratio between NaOH and acetylsalicylic acid is 1:1, the number of moles of acetylsalicylic acid is also 0.00582525 moles.
Step 4: Calculate the mass of acetylsalicylic acid.
Using the molecular weight of acetylsalicylic acid, which is 180.16 g/mol, we can convert the moles of acetylsalicylic acid to grams:
mass of acetylsalicylic acid = moles of acetylsalicylic acid × molecular weight
mass of acetylsalicylic acid = 0.00582525 mol × 180.16 g/mol
mass of acetylsalicylic acid = 1.0523 g
Step 5: Calculate the percentage of acetylsalicylic acid.
Using the given mass of the tablet, which is 1.18 g, we can calculate the percentage of acetylsalicylic acid:
percentage of acetylsalicylic acid = (mass of acetylsalicylic acid / mass of tablet) × 100%
percentage of acetylsalicylic acid = (1.0523 g / 1.18 g) × 100%
percentage of acetylsalicylic acid ≈ 89.1%
Therefore, the percentage of acetylsalicylic acid in the tablet is approximately 89.1%.