Question

II. Digestion of Acetylsalicylic acid(standard and tablet) with NaOH .

1. Digestion of Acetylsalicylic Acid Standard to Prepare Stock Solution:

Obtain ca. 0.1 g dried acetylsalicylic acid (MM = 180.16 g/mol), accurately weighed, and quantitatively transfer to a 125-ml Erlenmeyer flask. Add 5 ml 1.0 M NaOH and heat mixture to boiling on a hot plate. This will hydrolyze the acetylsalicylic acid to sodium salicylate. If necessary, rinse down the walls of the Erlenmeyer with DI water to ensure complete hydrolysis of the acid. Quantitatively transfer the sodium salicylate solution to a 25-ml volumetric flask and dilute to the mark with distilled water. This is known as the STOCK SOLUTION and will be used to prepare standards for calibration.

2. Digestion of Aspirin Tablet:

Weigh an aspirin tablet to the nearest 0.1 mg. Split the tablet in half and weigh to the nearest 0.1 mg the sample and place in a 125-ml Erlenmeyer flask. Process and dilute the half aspirin tablet as you did the acetylsalicylic acid standard.

III. Dilution to Prepare for Analysis:

1. Dilution of Stock Solution to prepare Acetylsalicylic Acid Standards

Prepare 10.00 ml acetylsalicylic acid standards by adding the appropriate amount of stock solution (Table 1) to a 10-ml volumetric flask and diluting to the mark with the iron chloride solution. Calculate the concentration of each standard (mg/L)

      Table 1. Volume of acetylsalicylic acid stock solution in preparation of standards

Standard Number	Volume of stock (mL)	[Acetylsalicylic Acid] (mg/L)
1	0.00
2	0.04
3	0.08
4	0.12
5	0.16
6	0.20

Answer 1

Standard Number I volume of Stock (ml) Acetyl salicylic acid (mg/L) 0.00 0.00 0.04 0.0000008 0.08 0.0000016 0.12 0.0000024 0:16 0.0000032 0.20 0.000204 . Concentration 9 Standard = concentration of Stock solm X volume of Stock flask volume Concentration on the stock M, V, X M2 V2 = Mvi solution where M, = Initial concentration v = Initial volume of more concentrated solution me = final concentration v = final volume of diluted solution

Concentration of the block yolution * MV, XMV 5 (0:1)(5ml) XM (25 mi) M = (0:1)(5 mi) 2 (as m') M = 0.02 M - 0.0 mm 0.0dy mi Conca of Standard number @ 10ml = 0.00008 M = 0.000000 8 mg 12