1. Calculate the molarity of a solution made by dissolving 0.4000 g of acetylsal
ID: 954006 • Letter: 1
Question
1. Calculate the molarity of a solution made by dissolving 0.4000 g of acetylsalicylic acid (180.15 g/mol) in 250.00 mL of water.
2. Calculate the volume of the solution prepared in (1) needed to make 100.00 mL of solution with a concentration of 4.00 x 10–4 M.
3. What are the correct units for molar absorptivity according to Beer’s Law?
4. Describe how you will determine the concentration of acetylsalicylic acid in your individual diluted aspirin-tablet solutions. (Hint: Think Beer’s Law Plot)
5. Set up the calculation for the concentration of acetylsalicylic acid in the undiluted 250-mL aspirin-tablet solution. (Assume a conc. of 3.60 x 10-4 M from the standard curve).
6. Set up the calculation for the mass percent of acetylsalicylic acid in the tablet your team tested. (Use your answer from previous question and use a total mass for the tablet of 0.4000g).
Explanation / Answer
1. Calculate the molarity of a solution made by dissolving 0.4000 g of acetylsalicylic acid (180.15 g/mol) in 250.00 mL of water.
moles of aspirin = mass / molar mass
= 0.400 / 180.15
= 2.22 x 10^-3
molarity = moles / volume (lit)
= 2.22 x 10^-3 / 0.250
= 8.88 x 10^-3 M
2. Calculate the volume of the solution prepared in (1) needed to make 100.00 mL of solution with a concentration of 4.00 x 10–4 M.
C1 = 8.88 x 10^-3 M , V1 = ?
C2 = 4.00 x 10^–4 M. , V2 = 100 mL
C1 V1 = C2 V2
8.88 x 10^-3 x V1 = 4 .00 x 10^-4 x 100
V1 = 4.5 mL
volume needed = 4.5 mL
3. What are the correct units for molar absorptivity according to Beer’s Law?
molar absorptivity units = M-1 cm-1
or M-1 mm-1
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