20 Questions
What is the purpose of liquid-liquid extraction?
To transfer a solute from one phase to another phase
Which apparatus is typically used for liquid-liquid extraction in the laboratory?
Separatory funnel
What type of compounds are usually extracted using liquid-liquid extraction?
Organic compounds from aqueous phases into organic phases
What reduces the electrostatic interactions between the solute and water in liquid-liquid extraction?
Charge neutrality of the solute
In liquid-liquid extraction, what is the basic requirement for a solute to be extractable from an aqueous solution to an organic solvent?
It should be uncharged or nonpolar
What is the basic principle of solvent extraction?
The solute dissolves preferentially in the more polar solvent
What does the partition coefficient (K) or distribution constant (KD) measure?
The hydrophilicity or hydrophobicity of a chemical substance
What properties must the organic solvent pair have in liquid-liquid extraction (LLE)?
Inertness and immiscibility with water
What is the aim of the experiment described in the text?
To determine the partition coefficient KD of I2 between water and CCl4 solvents
What is the purpose of adding H2SO4 and KI to the CCl4 layer in the procedure?
To facilitate titration against Na2S2O3 to determine iodine concentration
How is the partition coefficient (KD) related to the solubility of a solute in two immiscible solvents?
The partition coefficient measures how hydrophilic or hydrophobic a chemical substance is, by comparing the solubilities of the solute in the two liquids.
What are the essential properties of the organic solvent used in liquid-liquid extraction (LLE)?
- The solute must be more soluble in the solvent than in water. 2. The solvent must be immiscible with water and not form a homogeneous solution when mixed. 3. The solvent must be inert and not react with the solute. 4. The solvent should also be volatile so that it can be removed from the solute easily.
What is the aim of determining the partition coefficient (KD) of I2 between water and CCl4 solvents?
The aim is to determine how the solute (I2) is distributed between water and CCl4, by measuring its partition coefficient.
What is the procedure to determine the partition coefficient (KD) of I2 between water and CCl4 solvents?
- Add I2/CCl4 solution and D.W. to a separation funnel. 2. Shake the mixture for 30 minutes. 3. Let the mixture stand for 10 minutes for the layers to separate. 4. Pipette out CCl4 layer and perform titration against Na2S2O3.
How can you predict whether a solute is more soluble in the aqueous (aq) or organic (org) phase?
By knowing the partition coefficient of the solute, it can be predicted whether it is more soluble in the aqueous or organic phase.
What is the purpose of using a separatory funnel in liquid-liquid extraction?
To separate two immiscible phases and transfer a solute from one phase to another
What type of compounds are typically extracted using liquid-liquid extraction?
Organic compounds
What is the role of charge neutrality in the extractability of a solute in liquid-liquid extraction?
It reduces electrostatic interactions between the solute and water, lowering its aqueous solubility
What is the aim of using H2SO4 and KI in the CCl4 layer in the procedure?
To convert iodine (I2) into a nonpolar form for extraction
What properties must the organic solvent pair have in liquid-liquid extraction?
They should be immiscible and have different solubilities for the solute
Study Notes
Liquid-Liquid Extraction
- The purpose of liquid-liquid extraction is to separate and purify compounds based on their differences in solubility in two immiscible solvents.
Apparatus and Procedure
- A separatory funnel is typically used for liquid-liquid extraction in the laboratory.
- H2SO4 and KI are added to the CCl4 layer to increase the solvent's extracting power.
Extractable Compounds
- Typically, non-polar and slightly polar compounds are extracted using liquid-liquid extraction.
- Compounds with reduced electrostatic interactions with water, such as salts and ionic compounds, are more easily extracted.
Partition Coefficient (KD) and Solubility
- The partition coefficient (KD) measures the ratio of a solute's concentration in the organic solvent to its concentration in water.
- A high KD indicates the solute is more soluble in the organic solvent, while a low KD indicates it is more soluble in water.
- The partition coefficient is related to the solubility of a solute in two immiscible solvents.
Properties of Organic Solvents
- The organic solvent pair must have the following properties: immiscibility with water, high solubility for the analyte, and a density difference with water.
Aim and Purpose
- The aim of determining the partition coefficient (KD) is to understand the extractability of a solute from an aqueous solution to an organic solvent.
- The purpose of liquid-liquid extraction is to separate and purify compounds based on their solubility differences in two immiscible solvents.
Solute Extractability
- A solute is extractable from an aqueous solution to an organic solvent if it has lower electrostatic interactions with water, such as salts and ionic compounds.
- Charge neutrality plays a role in the extractability of a solute in liquid-liquid extraction.
This quiz covers the experiment on determining the partition coefficient of iodine between water and carbon tetrachloride using liquid-liquid extraction. It includes the concepts and procedures involved in this separation technique.
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