carboxylix acis

The carboxylic acid are only weak acids in water and only slightly dissociate, but they are strong enough to displace carbon dioxide from carbonates CH3CO2H(aq)——- CH3CO2 -(aq)+ H+ (aq)

1. Dissolve the impure compound in a minimum volume of hot (near boiling) solvent. An appropriate solvent is one which will dissolve both compound and impurities when hot and one in which the compound itself does not dissolve well when cold. The minimum volume is used to obtain a saturated solution and to enable crystallization on cooling • Hot filter solution through (fluted) filter paper quickly. This step will remove any insoluble impurities and heat will prevent crystals reforming during filtration • Cool the filtered solution by inserting beaker in ice Crystals will reform but soluble impurities will remain in solution form because they are present in small quantities so the solution is not saturated. Ice will increase the yield of crystals • Suction filtrate with a Buchner flask to separate out crystals The water pump connected to the Buchner flask reduces the pressure and speeds up the filtration. 5 Wash the crystals with distilled water To remove soluble impurities • Dry the crystals between absorbent paper

• Crystals lost when filtering or washing • Some product stays in solution after recrystallisation • other side reactions occurring