Respuesta :
Answer:
340.0mg of aspirin in the tested sample tablet
Explanation:
The titration of aspirin with NaOH obeys the following equation:
HC₉H₇O₄ + NaOH → C₉H₇O₄⁻ + Na⁺ + H₂O
As the complete titration spent 18.87 mL of 0.1000M NaOH, moles of NaOH are:
0.01887L × (0.1000mol / 1L) = 0.001887 moles of NaOH. As 1 mole of base reacts with 1 mole of aspirin, moles of aspirin are: 0.001887 moles of aspirin.
As molar mass of aspirin is:
C: 12.01g/mol × 9: 108.09g/mol
H: 1.01g/mol × 8: 8.08g/mol
O: 16g/mol ×4: 64g/mol
180.17g/mol. Mass of aspirin in the tested sample are:
0.001887 moles of aspirin × (180.17g / mol) = 0.3400g = 340.0mg of aspirin in the tested sample tablet
The actual mass of aspirin, in mg, in the tested sample tablet is 340 mg
Titrimetric analysis
From the question, we are to determine the actual mass of aspirin in the tested sample.
First, we will determine the concentration of the aspirin solution.
The balanced chemical equation for the reaction is
HC₉H₇O₄ + NaOH → NaC₉H₇O₄ + H₂O
Now, from the titration formula,
[tex]\frac{C_{A}V_{A} }{C_{B}V_{B}}= \frac{n_{A} }{n_{B}}[/tex]
Where [tex]C_{A}[/tex] is the concentration of the acid
[tex]C_{B}[/tex] is the concentration of the base
[tex]V_{A}[/tex] is the volume of the acid
[tex]V_{B}[/tex] is the volume of the base
[tex]n_{A}[/tex] is the mole ratio of the acid
[tex]n_{B}[/tex] is the mole ratio of the base
From the given information
[tex]V_{A} = 230 \ mL[/tex]
[tex]C_{B} = 0.1000 \ M[/tex]
[tex]V_{B} = 18.87 \ mL[/tex]
From the balanced chemical equation,
[tex]n_{A} = 1[/tex]
[tex]n_{B} = 1[/tex]
Putting the parameters into the formula,
[tex]\frac{C_{A} \times 230}{0.1000 \times 18.87} =\frac{1}{1}[/tex]
Then,
[tex]C_{A} \times 230 \times 1= 1\times 0.1000 \times 18.87[/tex]
[tex]C_{A} =\frac{1\times 0.1000 \times 18.87}{230 \times 1}[/tex]
[tex]C_{A} = 0.0082 \ M[/tex]
∴ The concentration of aspirin in the solution prepared is 0.0082 M
Now, we will determine the number of moles of aspirin in this solution
Using the formula,
Number of moles = Concentration × Volume
Volume of solution = 230 mL = 0.230 L
Number of moles of aspirin in the solution = 0.0082 × 0.230
Number of moles of aspirin in the solution = 0.001886 mole
Now, for the mass of aspirin in the tested sample tablet
From the formula,
Mass = Number of moles × Molar mass
Molar mass of aspirin = 180.158 g/mol
∴ Mass of aspirin in the tested sample = 0.001886 × 180.158
Mass of aspirin in the tested sample = 0.339778 g
Mass of aspirin in the tested sample = 339.778 mg
Mass of aspirin in the tested sample ≅ 340 mg
Hence, the actual mass of aspirin, in mg, in the tested sample tablet is 340 mg
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