Answer the following questions about acetylsalicylic acid, the active ingredient
ID: 1067844 • Letter: A
Question
Answer the following questions about acetylsalicylic acid, the active ingredient in aspirin. The amount of acetylsalicylic acid in a single aspirin tablet is 325 mg, yet the tablet has a mass of 2.00 g. Calculate the mass percent of acetylsalicylic acid in the tablet. The elements contained in acetylsalicylic acid are hydrogen, carbon, and oxygen. The combustion of 3.000 g of the pure compound yields 1.200 g of water and 3.72 L of dry carbon dioxide, measured at 750. mm Hg and 25 degree C. Calculate the mass, in g. of each clement in the 3 000 g sample. A student dissolved 1.625 g of pure acetylsalicylic acid in distilled water and titrated the resulting solution to the equivalence point using 88.43 mL of 0.102 M NaOH (aq). Assuming that acetylsalicylic acid has only one ionizable hydrogen, calculate the molar mass of the acid. A 2.00 times 10^-3 mole sample of pure acetylsalicylic acid was dissolved in 15.00 mL of water and then titrated with 0.100 M NaOH(aq). The equivalence point was readied after 20.00 ml. of the NaOH solution had been added. Using the data from the titration, shown in the table below, determine the value of the acid dissociation constant, K_0, for acetylsalicylic acid and the pH of the solution after a total volume of 25.00 mL of the NaOH solution had been added (assume that volumes are additive).Explanation / Answer
(a) % mass of salicilic acid = (mass of sailicilic acid / mass of tablet) * 100
% mass = (0.325 g. / 2.00 g. ) * 100 = 16.25 %
(b) moles of H2O = 1.20 /18 = 0.0667 mol
1 mol H2O = 2 mol H
0.0667 mol H2O = 0.133 mol H
Then, mass of of H = 0.133 * 1 = 0.133 g.
Assuming ideal behaviour,
n = P V / R T = (750/760) * 3.72 / (0.0821 * 298.15) = 0.150 mol of CO2
1 mol CO2 = 1 mol C
then, 0.150 mol CO2 = 0.150 mol C
Now, mass of C = 0.150 * 12 = 1.8 g.
Therefore, Mass of Oxygen = 3.000 - 0.133 - 1.80 = 1.067 g.
(c) Moles of NaOH used = 0.102 * 88.43 / 1000 = 0.00902 mol
1 mol NaOH can neutralise 1 mol salicilic acid,
then 0.00902 mol NaOh can neutralise 0.00902 mol salicilic acid.
we know that,
number of moles = mass / molar mass
Molar mass = 1.625 / 0.00902 = 180.16 g/mol