16 Questions
What is the purpose of extraction?
Separating and purifying organic substances.
What is the principle behind extraction?
The difference in solubility of an organic substance in two different immiscible solutions.
Why is it necessary to repeat the extraction process multiple times?
To ensure that all of the substance is withdrawn from the original solvent.
What is the ratio of the concentrations of solute in the two solvents known as?
The distribution or partition coefficient (KD).
What are the desirable properties of an extracting solvent?
Immiscibility, favorable KD, non-reactive, low boiling point, and easy separation from solute.
Why is water often used as one of the solvents in extraction?
Because it is a common solvent and doesn't react with most organic compounds.
What type of organic solvents are often used in extraction?
Non-polar or slightly polar organic liquids.
Why is ether an important organic solvent in extraction?
Because it is extensively used as an extracting solvent due to its favorable properties.
What is the effect of adding a small amount of an ionizable salt like NaCl or K2CO3 to the water layer?
It increases the polar property of the solution, resulting in a decrease in the solubility of the non-polar compound.
What are some examples of low-boiling organic solvents used in this experiment?
Pentane, hexane, tetra chloromethane, chloroform, benzene, and toluene.
What is the purpose of shaking the mixture well for 10 minutes in the separatory funnel?
To allow for thorough mixing and contact between the aqueous and organic layers.
What happens to the color of the organic layer when iodine is dissolved in it?
It changes color.
Why is it necessary to open the stopper for a while during the extraction process?
To release excess pressure.
How can the extraction efficiency be calculated?
By titrating the aqueous layer with sodium thiosulfate.
What is an advantage of doing the extraction in multiple batches using different volumes of chloroform?
It allows for the calculation of the percentage extraction (E%).
What is the purpose of using potassium iodide in the extraction process?
It helps to increase the solubility of iodine in water.
Study Notes
Extraction Purpose and Theory
- Extraction is a crucial method for separating and purifying organic substances from natural products like seeds and leaves of plants.
- It relies on the difference in solubility of an organic substance in two immiscible solutions, such as water and chloroform.
Extraction Process
- The process involves finding a solvent (b) that can dissolve the substance (x) and does not mix with the original solvent (a).
- The solute is distributed between the two unmixed liquid layers according to the distributive law.
- The upper layer is the liquid of lower density, and the lower layer is the liquid of higher density.
- Multiple extractions may be necessary to ensure all substance (x) is withdrawn from solvent (a).
- The ratio of the concentrations of solute in the two solvents is known as the distribution or partition coefficient (KD).
Characteristics of an Extracting Solvent
- An extracting solvent should be immiscible, have a favorable KD, not react with other solvents, have a low boiling point, and be easily separated from the solute.
Common Extracting Solvents
- Ether is a commonly used extracting solvent, slightly soluble in water, and its efficiency can be improved by adding a small amount of an ionizable salt to the water layer.
- Other low-boiling organic solvents used in this experiment include pentane, hexane, tetra chloromethane, chloroform, benzene, and toluene.
Procedure for Iodine Extraction
- Mix 0.05g of iodine and 1.5g of potassium iodide in a beaker with 50ml water, then add 7.5ml of chloroform.
- Shake the mixture well and release excess pressure before allowing the layers to separate.
- Note the dissolution of iodine in the organic layer through the color change of the organic layer.
- Separate the lower layer (chloroform) slowly, and calculate the E% extraction by titrating the aqueous layer using sodium thiosulfate.
Learn about the extraction method for separating and purifying organic substances, including its theory and applications in natural products.
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