3 of 3 - + Automatic Zoom : Aspirin, acetylsalicylic acid (MM = 180.157 g/mol),
ID: 545717 • Letter: 3
Question
3 of 3 - + Automatic Zoom : Aspirin, acetylsalicylic acid (MM = 180.157 g/mol), is a monoprotic acid. A student synthesizes some aspirin and then analyzes it using sodium hydroxide solution that they standardized in an earlier experiment. The student dissolved 400.0 mg of the sample they synthesized in 250 mL of water. The titration analysis required 29.45 mL of 0.0745 M NaOH. How many mg of aspirin was in their sample? What is the percent aspirin in their sample? (Note: You do not need the formula for aspirin to complete this problem. What is the reaction between ANY monoprotic acid and NaOH?) [15 points] 6)Explanation / Answer
HA (acid) + NaOH ----------------------> NaA + H2O
moles of acid = moles of NaOH
moles of NaOH = 29.45 x 0.0745 / 1000 = 2.194 x 10^-3
moles of NaOH = moles of aspirin = 2.194 x 10^-3
mass = moles of aspirin x molar mass
= 2.194 x 10^-3 x 180.157
= 0.395 g
= 395 mg
in the sample 395 mg aspirin is present
percentage = 395 x 100 / 400
= 98.8 %
percentage of aspirin = 98.8 %
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