Aim:
To separate a mixture of carboxylic acid and a neutral substance by treatment with aqueous sodium hydroxide and purifying the carboxylic acid, measuring the melting points of the neutral and the acid components.
METHOD:
A mixture of( 5g) Carboxylic acid and neutral compound were separated by adding 2 mol dm-3 sodium hydroxide (25cm3) to the mixture, which separated the water soluble sodium from the water insoluble neutral component, by filtration. The solid at the filter was washed with 10cm3of water twice and the solid was dried and the melting point was measured.
Concentrated hydrochloric acid was then added to the alkaline filtrate to recover the acid component, the solution was then cooled in an ice bath, and the precipitate was filtered. Hydrochloric acid was again added to the filtrate to make sure all the acid component has precipitated. It was then crystallized from water by boiling and letting it cool again.
RESULTS
Mass of the mixture taken =5.752g Mass of the neutral component =2.261g Mass of the carboxylic acid component =1.483g mp of the neutral component =81⁰c-83⁰c mp of the acid component
OBSERVATION:
It was observed that the mass of the neutral component was higher than the mass of the carboxylic acid component.
CONCLUSION:
The difference between the mass of the starting mixture and the resulting masses of the acid component and neutral component combined may have been caused by the loss of some of the solids during purification, as they may have been left in filter papers and beakers. A measurement was not obtained for the melting point of the acid component because of time restrictions.
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