Question

Describe and explain the possible effect on your results of the following experimental errors or variations. In each case , specify the components whose percentages would be too high or too low. (a) after adding dichloromethane to panacetin, you didnt stir or shakethe mixture long enough. (b) during the NAHCO3 extraction you failed to mix the aqueous and organic layers thourouglhy . (c) you mistakelny extracted the dichloromethane solution with 5% HCI rather than 5% NaHCO3. (d) instead of using pH paper, you neutralized the NaHCO3 solution to pH 7 using litmus paper.

Answer 1

a-Due to incomplete dissolution of dichloromethane , the crystals of sucrose would not form as much as it form at the bottom of the Erlenmeyer flask.As we needed to filter the sucrose from the aspirin and dichloromethane. So the yield is low.

b-when during the NAHCO3 extraction you failed to mix the aqueous and organic layers thourouglhy, you shoud not able to accurately extracting the aspirn from dichloromethane.% of both of them is not accurate.

c- whenyou mistakelny extracted the dichloromethane solution with 5% HCI rather than 5% NaHCO3,then HCl protonate the aspirin and it is present in organic layer.HCl makes the aspirin as acetylsalicylic acid .

d-By use of litmus paper accurate results would not be visible because at pH7 the HCO3 wouldnt be able to act as a base and extract a proton from aspirin. At this pH HCO3 is itself protonated so cannot react with aspirin.