INFO NEEDED FOR THE FOLLOWING TWO QUESTIONS: A aspirin tablet is dissolved in 25
ID: 695277 • Letter: I
Question
INFO NEEDED FOR THE FOLLOWING TWO QUESTIONS:
A aspirin tablet is dissolved in 250.0 mL of water. A 0.10 mL sample of the solution is diluted to 10.00 mL and this diluted solution has an absorbance reading of 0.110. The spectrophotometer was calibrated and the equation for the standard curve is found to be: y=1538X - 0.01 where Y is the absorbance at 530nm and X is the molarity of an acetyl salicylic acid solution. The concentration of the diluted solution was measured to be 7.802 x 10^-5 M.
1. Remembering that the solution in the previous question was formed by a dilution of 0.10 mL to 10.00 mL in order to read the absorbance, what is the molarity of the original solution?
2. What is the total weight (mg) of acetyl salicylic acid in the aspirin tablet? The original solution had a volume of 250.0 mL.
Explanation / Answer
Absorbance reading = 0.11
Concentration of dilute solution = 7.802 x 10-5 M
1.
M1 V1 = M2 V2
7.802 x 10-5 M * 10 mL = M2 * 0.1 mL
Molarity of original solution, M2 = 7.802 x 10-3 M
2.
Total moles of acetyl salicylic acid in original solution = M2 * 250 mL / 1000 (mL/L)
= 0.00195
Molar mass of acetyl salicylic acid = 180.157 g/mol
Weight of acetyl salicylic acid in original solution = 0.3514 g
= 351.4 mg