Incorrect Practical Q's

suggest why ethanoic anhydride is preferred to ethanoyl chloride for preparing aspirin

less corrosive

role of H3PO4 in producing aspirin

catalyst

suggest why reflux is not essential when flask is heated to 85^oC for 10 minutes

boiling points of reactants above 85^oC

describe two ways that testing melting point would show a product is impure (producing aspirin)

• melting point lower than data book value

• melts over a wide range of temperatures

draw a diagram to show how an impure solid is filtered under reduced pressure

describe the process of recrystallisation for purifying aspirin/6

• dissolve crude product in minimum volume

• of hot solvent

• filter whilst hot

• leave to cool

• filter under reduced pressure with Buchner funnel

• wash with water and dry with pieces of filter paper

NaOH reacts with ethyl benzoate to produce benzoic acid

suggest why an excess of NaOH is used in making benzoic acid

ensures all the ethyl benzoate is completely reacted

state why reflux is used in this hydrolysis/1

prevents reactant vapours from escaping, returned to reactant mixture

suggest why sodium benzoate is soluble in cold water but benzoic acid is insoluble in cold water/2

• sodium benzoate is ionic and therefore very soluble

• benzoic acid has a non polar benzene ring making it insoluble

suggest why the percentage yield of recrystallisation was more than 100% /1

products were not dried properly

give two practical steps needed before recording the initial burette reading/2

• make sure there are no air bubbles

• remove the funnel