Hello there. I have a few short questions about a lab report I’m working on. It

Question

Hello there. I have a few short questions about a lab report I’m working on. It is for ORGANIC CHEMISTRY 1. The experiment is TO QUANTITATIVELY SEPERAE AND IDENTIFY AN UNKNOWN MIXTURE BY EXTRACTION RECRYSTALLIZATION AND MELTING POINT DETERMINATION I have also included the procedure, question one is step one where it talks about putting it in ice and question 2 is step7, why are they more effective Please try to help me out it’s so much needed thank you!!!!! 0 384 hiphenyl omine Questions to be answered in the Lab Report 1) Why do you need to use ice cold water for the washes? 2) We state that: Four extractions with 5 ml each are much more effective than two extractions rec with 10 mL each. Why is this? You might need to use math. 7 3) What intermolecular interactions are responsible for the decrease in solubility in the aqueous solvent after deprotonation? 0) Watch Glass Round Melting Port lasse S.3C 9 of 10 1365

Explanation / Answer

1)

In hot water the compound might get soluble and was away with water.

2)

Transferring a solute from one solvent into another is called Extraction, or more precisely, liquid-liquid extraction. The solute is extracted from one solvent into the other because the solute is more soluble in the second solvent than in the first. When a solution (solute A in solvent 1) is shaken with a second solvent (solvent 2) with which it is not miscible the solute distributes itself between the two liquid phases. When the two phases have separated again into two distinct solvent layers, and equilibrium will be achieved such that the ratio of the concentrations of the solute in each layer is defined by a constant. The constant, called the distribution coefficient (or partition coefficient) K, is defined by

K = C2/C1
where C1 and C2 are the concentrations at equilibrium, in grams per liter (or milligrams per milliliter) of solute A in solvent 1 and in solvent 2, respectively. This relationship is a ratio of two concentrations and is independent of the actual amounts of the two solvents mixed. The distribution coefficient has a constant value for each solute considered and depends on the nature of the solvent used in each case.

Every time an extraction is carried there will be mass transfer of solute from solvent 1 to solvent 2.
The solute will distribute itself in the two liquid phases and a new equlibrium will be estblished to achieve K - the partition coefficient which is constant

Therefore multiple small extractions that generate multiple equilibrium stages of mass transfer of solute are more efficient than a single extraction which involves a single equilibrium stage of mass transfer of solute . Considering the fact that the partition coefficient of solute between the two solvents is independent of the quantity of solvent being used for extraction a large volume of solvent in a single extraction is just adding cost without any value addition.

3)

The dissolving process involves 3 intermolecular attraction forces, which dictate how soluble a solute is in a solvent, or whether it is soluble at all.

There are attractive forces between solute-solute molecules, between solvent-solvent molecules, and between solute-solvent molecules. In order for something to dissolve, the solute-solvent forces must be able to overcome the solute-solute and solvent-solvent attractions. If the solute-solvent forces are less then these forces, the solute will normally not dissolve significantly.

Note: A "solute" is the substance dissolved, and a "solvent" is the substance dissolving it. Solvents are normally liquid, though they can be a solid or a gas.

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