exam specific answers (carboxylic acids and derivatives)
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required practical 10 suggest why ethanoic anhydride is preferred to ethanoyl chloride for this preparation? (1)
it doesn’t produce HCl
required practical 10 suggest why reflux is not essential when the flask is heated to 85 degrees for 10 minutes? (1)
the boiling points are above 85 degrees
required practical 10 what would be needed in a diagram to show how an impure solid is filtered? (2)
• funnel top and bottom shown open • bung drawn with funnel spout going through it • Buchner flask • horizontal filter paper • labels - filter paper and vacuum
required practical 10 describe the recrystallisation process used to purify the aspirin - incude the method and apparatus used (6)
• dissolve crude product in hot solvent • of minimum volume • filter to remove insoluble impurities • cool to recrystallise • filter under reduced pressure with Buchner apparatus • wash with cold solvent and dry
explain how carbon dioxide causes global warming. (2)
• C=O bonds in CO2 absorb infrared radiation • IR radiation emitted by the Earth doesn’t escape from the atmosphere
State why reflux is used in this hydrolysis. (1)
doesn’t allow any reactant vapours to escape
Suggest why sodium benzoate is soluble in cold water but benzoic acid is insoluble in cold water. (2)
• sodium benzoate is soluble because it is ionic • benzoic acid is insoluble because even though COOH group is polar, benzene ring is non-polar