Consider the following solvent pairs. If mixed together, which pairs would form
ID: 519526 • Letter: C
Question
Consider the following solvent pairs. If mixed together, which pairs would form two layers? If they form two layers, which solvent would be on top? Acetone and toluene Methanol and hexanes Hexanes and methylene chloride Hexanes and water Chloroform is an excellent solvent for extracting caffeine from water. The distribution coefficient K_D = (C chloroform)/(C water) for caffeine in chloroform - water is 10 degree C at room temperature. Find the mass of caffeine that would be removed from a solution 4.0 g of caffeine in 100 ml of water using a single extraction of 100 ml of chloroform.Explanation / Answer
1)
Acetone and Toluene:(immiscible)
Density of acetone = 791kg/m3
Density of toluene = 867 kg/m3
Therefore, Acetone would be on top as its density is lower than Toluene.
Methanol and hexanes:(partially miscible)
Density of methanol = 792kg/m3
Density of Hexane = 655 kg/m3
Hexane layer will be on the top of the methanol layer because the density of methanol is higher.
Hexane and methylene chloride:( miscible)
Density of Hexane = 655kg/m3
Density of methylene Chloride = 1330kg/m3
Hexane and water(immiscible)
Density of Hexane = 655kg/m3
Density of water = 1000kg/m3
Therefore, the layer of Hexane will be on top of the layer of water.
2) Solubility of caffeine in water = 1.8g/100ml
Solubility of caffeine in chloroform = 18.0g/100 ml
Caffeine prefers chloroform 10 times more than water.
4.0 grams of caffeine = 3.6 gms in the organic layer + 0.4 grams in the aqueous layer.
Therefore, 3.6 gms of caffeine can be extracted.