EXP 6: extraction
List the procedural steps, from start to finish, that are required to perform a chemically active solvent extraction of a three-component mixture composed of benzoic acid, benzocaine, and a neutral organic molecule all dissolved in dichloromethane.
1. dissolve solid 3-component mixture in dichloromethane and place in separatory funnel. add 6m HCL to solution. shake and sllow to settle into layeres 2. add water to dissolve brown emulsion bw layers 3. separate and collect aw layer in flask, and add base 4. place dichloromethan layer back in separatory funnel and extract it with 3< NaOH. allow layerse to settle 5. add water to dissolve white gel-like emulsion 6. sep and collect aw layer in flas, add acid 7. collect and dry solids in both erlenmeyer flask and filtration
During a solvent extraction between water and an immiscible solvent, a student has two layers in their separatory funnel and then shakes it. A single, milky liquid develops and no real sign of any layers are visible. What has occurred and what should the student do?
1. first, add small quantity of water. if doesnt work, add solvent 2. an emulsion has formed
A sample of an unknown liquid has a mass of 18.44 g, and a volume of 7.04 mL. What is the density of this liquid?
2.62 g/cm3
During a solvent extraction, a student lost track of which layer was the aqueous layer and which was the organic layer. What simple, non-destructive test could be used to determine which layer is which?
Add a little distilled water to see which layer the water adds to.
Eugenol, the essential oil found in cloves, is insoluble in water. The alcohol group in eugenol is dramatically more acidic than regular straight-chain alcohols. How could eugenol (shown below) be separated from a mixture of other non-acidic molecules?
Dissolve the mixture in dichloromethane, shake with sodium hydroxide, collect the aqueous layer, and reacidify to force precipitation of the eugenol.
acidic aw waste
HCl acid solution
Purpose: Dissolve the emulsion due to the benzocaine salt exceeding its solubility.
Procedure: add water to sep funnela that contains an acidified three-component mixture in dichloromethane
Which of the following statements best describes density?
The ratio of a substance\'s mass to its volume, measured in g/mL and also equivalent to g/cm3.
The solubility data table shows that both benzoic acid and benzocaine are significantly more soluble in ethanol than they are in water. Why is ethanol not a suitable solvent for the solvent extraction of benzoic acid and benzocaine from aqueous solution?
ethanol is miscible with water
hold your thumb firml over hole in the top of the funnel during shaking
false
students hsould throw away the first layer and acid washes
false
To get effective mixing in a separatory funnel, the combined level of liquids should not exceed:
higher than the widest part of the separatory funnel
does density always increase as molar mass increases
no
purpose: to recover mixture in case of stopcock leaks
procedure: place beaker below sep funnel
purpose:Convert the benzoic acid into a water-soluble salt.
procedure:add aq base to mixture dissolved in dichloromethane
purpose:To avoid a build up of pressure inside the glassware.
procedure:vent separatory funnel through stopcock
basic aq waste
sodium hydroxide solution
A separatory funnel contains the two immiscible liquids water and tetrahydrofuran. Use the given densities to determine which layer is on top and which is on the bottom in the binary mixture.
top layer = tetrahydofuran bottom layer = water
If one is going to re-extract the upper layer with another volume of liquid, the upper layer can be left in the separatory funnel and fresh solvent added to the funnel.
true
The first step in using a separatory funnel for extraction is to make sure the funnel stopcock is closed and then carefully pour the liquid to be extracted into the funnel.
true
stopcock can be used to vent excess pressure if either of the liquids are warm to tougha nd has a low boiling point
true
