Problems and questions 1. Irritation of the stomach is caused by what functional

Question

Problems and questions 1. Irritation of the stomach is caused by what functional group on the aspirin molecule? If a bottle of aspirin tablets has the aroma of vinegar, it is time to discard those tablets. Explain why, and include the chemical equation for the hydrolysis of aspirin in the explanation 2. 3. Why is starch added to aspirin? 4. In step B.9 of this experiment, excess acetic anhydride is destroyed by the addition of water, which converts the anhydride into acetic acid. Write the balanced equation for this reaction. 5. FeCl, is used to test for the presence of unreacted salicylic acid in this experiment. A chemistry journal article from 1941 described using salicylic acid to test for the presence of Fe". Instead of using salicylic acid, its sodium salt (sodium salicylate) was used because the salt is more soluble in water than the carboxylic acid. Sodium salicylate is prepared by reacting salicylic acid with sodium hydroxide. Write the neutralization reaction of salicylic acid with NaOH to produce sodium salicylate. Remember, the other product is water.

Explanation / Answer

Q1

pH at stomach is very acidic, i.e. pH < 3

pKa for aspirin is about 3-4

then, the aspirin molecular C9H8O4 (protonateD) compound is what "hurst" the stomach (carboxilic acid COOH)

Q2

note that aspirin is acetylsalycilic acid, when it has vinegar "odor"

when exposed to water, it will break down back to

salycilic acid + acetic acid, therefore, acetic acid is the "vinegar" odor

Q3

starch is added --> binding agnet + filler

It helps to have a "pill" sized dose. Instead of 500 mg of pure aspirin.

It also aids in the distribution of the acid

Q4

(CH3CO)2O + H2O <--> 2CH3COOH

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