The Effect Of Solubility On The Solubility Of The Solute And Solvent

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Solubility is the property of a solid, liquid or gaseous chemical solute to dissolve in a solid, liquid or gaseous solvent to form a solution [1]. The solubility of a particular substance is dependent on the physical and chemical properties of both the solute and solvent [1]. The temperature, pressure and pH of the solution also has an effect on the solubility. The extent of the solubility of a certain solute in a particular solvent is measured as saturation, where adding more solute will not increase the concentration of the solution and will precipitate the excess in the solution. Phase transfer reagents are used to facilitate movement of a reactant from one phase to another [2]. For example, from the aqueous phase to the organic phase. They accelerate reaction rates, minimize solvent waste and enable the use of an inexpensive nonpolar aprotic solvents and water instead of using more expensive high-polar solvents [2]. Inorganic salts (such as the Potassium permanganate used in this experiment) are often soluble in an aqueous phase but insoluble in an organic phase in the absence of a phase transfer reagent. It is commonly either a large hydrophobic counter ion such as tetrabutylammonium bromide or a macrocyclic ligand such as 18-crown-6 or triethylene glycol. Recrystallization is a procedure used for purifying compounds [1]. The compound is dissolved in the minimum amount of hot solvent, and as the solution is slowly cooled the compound precipitates out, leaving the soluble impurities in solution [1]. If there are insoluble impurities present in very small quantities, they can be separated from solid crystals by filtration. The solvent is deliberately picked, as the compound must be more soluble at higher temperatures and less ... ... middle of paper ... ...tassium cations from the potassium permanganate, encapsulating them, leaving lipophilic cations. These molecules have a hydrophilic interiors containing the anion and a hydrophobic exterior, which will readily dissolve in the non-polar solvent [3]. This also results in the permanganate dissolving in the toluene. Triethylene glycol is more effective than 18-crown-6 because of the more open structure. In general, ammonium salt catalyst undergoes anion exchange with the anion of the solute in the aqueous solution and this new pair can now diffuse into the organic phase due to its now lipophilic nature [4]. It then transfers the displaced anions back to the aqueous phase to start over. In this experiment, the tetrabutylammonium bromide causes the permanganate ion to transfer into the toluene by having the bromide ion and the permanganate ion switch places and phases.

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