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Exam 3 - Exam 3 The solubility of any compound in different...

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Exam 3 The solubility of any compound in different solvents depends on the physical and chemical structure of the solvent and the solute, as well as the environment its in (temperature, pH, and pressure). Saturated Solubility is the solution at which the solute in the solution phase is in equilibrium with the solute phase(solid or liquid). This means if we’re trying to dissolve a solute, I’m going to put excess of the solute and then add solvent and shake for some time, until there is equilibrium. This equilibrium is the number of molecules of the solute leaving the solute layer equals the number of the solute returning to the solute layer. (see diagram drawn *if its an endothermic solubility we expect the extra solute precipitation or I’m going to form a supersaturated solution ) So the definition of a supersaturated solution is a solution that is holding an amount of solute above its saturated solubility. To prepare such a solution, the solution is prepared at higher temperature then cooled. To convert supersaturated solution into a saturated solution is by adding 1 crystal (seed) of my substance or another substance, or by agitation the solution. Sometimes the final solution that is formed is less than the supersaturated solution. Generally like dissolves like. Polar solvents can dissolve polar solutes. Polar solvents reduce the forces of attraction between oppositely charged ions of the solute. (water and NaCl). If the solute has the ability to form hydrogen bonding with the solvent that also increases its solubility. Non polar solvents increase the solubility of non polar substances like lipophilic drugs and excipients. Examples of non polar solvents are oils, fats, mineral oils. Gas Solubility There are some factors that affect the solubility of gases in liquids; Temperature decreases the solubility of a gas. Pressure can increase solubility. To describe the solubility of gases in liquids we use Henry’s Law. Henry’s law applies only to NONREACTING GASES. This law states that the C=Sigma x P. C is the concentration of the dissolved gas with units sometimes of mole/L, Gram/L or Mole fraction. P is the partial pressure, the pressure above the liquid with units sometimes of atmospheres or mmHg. Sigma is the solubility coefficient (it is the inverse of the Henry’s law constant k) Unit of this constant Sigma depends on what units we used for concentration and pressure. The higher the gas pressure the higher the solubililty. When it comes to temperature the lower the temperature the higher the gas solubility, how much depends on what type of gas your dealing with. Oxygen concentration doesn’t change much with change in temperature, but for CO2 can change substantially. At high temperature the gas expands and its tendency to escape increases, also at high temperature the gas molecules acquire more kinetic energy and allows the molecules to break the intermolecular bonds and escape. This explains why at higher temps the concentration of gas decreases in the solution because when u heat the gas it has more energy that allows it move out of the solution, and the gas expands so it moves
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upwards and leaves the solution.
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