Preparation of benzoic acid
Place 10 drops of methyl benzene , 10cm3 of water, 0.1g of sodium carbonate
and 1g of potassium manganate(VII) into a 50cm3 flask. Reflux the mixture
for 1 hour. Cool the mixture, and acidify with dilute sulphuric
acid. Add sodium metabisulphite to remove manganese dioxide. Filter
the white crystals of benzoic acid. Benzoic acid can be recystallised from
hot water. Melting point = 121oC.
Task 5.3(a)(ii).1 Describe in detail the steps needed to prepare a pure sample of benzoic acid from methyl benzene including the steps needed to determine the reaction yield.
Task 5.3(a)(ii).2 Calculate the yield of benzoic acid if 0.96g of methyl benzene forms 1.00g of benzoic acid. Explain why the yield is less than 100%.
Task 5.3(a)(ii).3 Explain how the melting point of the benzoic acid can be determined. What can be concluded about the product if its melting point is found to be 119oC?