1. describe 3 properties of good extraction solvents 2. After separating layers
ID: 910578 • Letter: 1
Question
1.describe 3 properties of good extraction solvents
2. After separating layers in an extraction, it is necessary to dry the organic layer with a substance that absorbs water. explain why this is necessary
3. suggest two methods for determining which layer in an extraction is the aqusous layer and which layer is the organic layer.
4. phenol and benzoic acid are both weak acids that are soluble in diethyl ether and insoluble in water. benzoic acid is soluble in both 10% NaOh and 10% NaHCO3, Phenol is soluble only in the stronger base, 10% NaOH. From this information, write a flow scheme for separating and recovering phenol and benzoic acid
Explanation / Answer
(1) i. The good extraction solvent is one in which the solute is easily soluble.
ii. Solvent is highly volatile.
iii. For liquid - liquid extraction the solvent must be immisible with other solvent
(2) To remove any contaminated water particles from orgnic layer, after separating layers in an extraction, it is necessary to dry the organic layer with a substance that absorbs water generally with Calcium chloride.
(3) Add a drop of water to the top layer, if it immediately dissolves completely, the layer is aqueous layer.
On the other hand if it is not misible with the layer, the layer is organic layer
(4) Dissolve the phenol and benzoic acid mixture in diethyl ether.
Then first add 10% NaOH solution to the mixture. Since only benzoic acid reacts with 10% NaOH solution to form sodium benzoate, it enters in to aqueous layer and phenol remains in organic layer.
Finally queous layer is treated with HCl solution to crystallise benzoic acid.
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