CHEM 104 Homework 6 20 points-Ch. 19.1, 19.2 Aspirin is one of the most widely u
ID: 702227 • Letter: C
Question
CHEM 104 Homework 6 20 points-Ch. 19.1, 19.2 Aspirin is one of the most widely used and versatile medicines, used for treating pain, controling fever, and preventing heart attacks and blood clots. The active ingredient in aspirin in acetylsalicylic acid. From the experimental information below, determine the molar mass of acetylsalicylic acid and its K, value. State any assumptions you must make to find your answer! 4. A 2.51 g sample of acetylsalicylic acid is titrated exactly with 27.36 mL of 0.5106 M NaOH solution. Addition of 13.68 mL of 0.5106 M HCI to the resulting mixture produces a solution with pH 3.48. Data:Explanation / Answer
no of moles of NaOH used = 0.5106 x 27.36 = 13.97 mmol
no fo moles of NaOH used = no of moles of aspirin = 13.97 mmol = 0.01397 mol
mass of aspirin in sample = 180.17 x 0.01397 = 2.51 g
no of moles of HCl addeed = 0.5106 x 13.68 = 6.99 mol
as this is exctly half the no of moles of salicylic acid present in the mixture = 13.97/2 = 6.99 mmoles
thus pH = pKa = 3.48
pKa of aspirin = 3.48
Ka = 10-3.48 = 3.3 x 10 -4