Analysis of Aspirin - Analysis of Aspirin Objective: The...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Analysis of Aspirin Objective: The objective of this experiment is to determine the purity of a sample of aspirin. Introduction: Acetylsalicylic acid, aspirin can be prepared by the reaction of salicylic acid and acetic anhydride. C C C C C C H O C H H H H C C H H H O O H C O C H H H C C C C C C H O H H H + O O H O C C O O CH 3 CH 3 C O O H salicylic acid acetic anhydride acetylsalicylic acid acetic acid + The synthesis of aspirin is commonly carried out in general and nursing chemistry labs to illustrate an organic reaction. If the aspirin is not kept dry it can decompose to form salicylic acid and acetic acid, the reverse of the synthesis reaction shown above. c c c c c c C OH H H H H O OH C H H H C OH O + c c c c c c C O H H H H O OH + C O CH 3 H 2 O In this experiment you will determine the purity of aspirin prepared in your previous lab by using a titration. The first reaction that will be carried out is an acid – base reaction between the carboxylic acid of the aspirin with sodium hydroxide solution. c c c c c c C O H H H H O OH C O CH 3 + OH 1- c c c c c c C O H H H H O O 1- C O CH 3 + H 2 O If there were no acidic impurities in the aspirin, you could determine the purity of the aspirin using a direct titration of the aspirin with standardized base. However if there are acidic impurities, they will also react with the base increasing the amount needed to reach the endpoint. In order to determine the amount of aspirin in your sample you will react the substance with additional base at elevated temperature, according to the following reaction:
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
c c c c c c C O H H H H O O 1- C O CH 3 + OH 1- c c c c c c C OH H H H H O O 1- + H 3 C C O 1- O This reaction represents a “base-promoted hydrolysis” or saponification reaction. After you neutralize all of the acidic material in your sample you will add a known excess of NaOH solution to cause this reaction to occur. The excess base that is not used in the hydrolysis reaction will then be titrated with a standardized hydrochloric acid solution. This is called a “back-titration”. From the data you collect you will be able to determine the amount of aspirin that is in your sample. Protocol: Your group will perform two trials. 1. Using the analytical balance, mass approximately 0.5 g of the aspirin sample into a clean dry 250-mL Erlenmeyer flask. 2. Prime and fill two 50-mL burets (one with the standardized acid and the other with the standardized
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 10

Analysis of Aspirin - Analysis of Aspirin Objective: The...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online