3-Properties of Solutions-I.pdf

Properties of Solutions I Dr. Alya A. Arabi College of Medicine and Health Sciences UAEU The Solution Process • A solution is a homogeneous mixture of solute (present in smallest amount) and solvent (present in largest amount). • Solutes and solvent are components of the solution. • In the proce...

Properties of Solutions I Dr. Alya A. Arabi College of Medicine and Health Sciences UAEU The Solution Process • A solution is a homogeneous mixture of solute (present in smallest amount) and solvent (present in largest amount). • Solutes and solvent are components of the solution. • In the process of making solutions with condensed phases, intermolecular forces become rearranged. The Solution Process The Solution Process • Consider NaCl (solute) dissolving in water (solvent): – – – – – the water H-bonds have to be interrupted, NaCl dissociates into Na+ and Cl-, ion-dipole forces form: Na+ … -OH2 and Cl- … +H2O. We say the ions are solvated by water. If water is the solvent, we say the ions are hydrated. The Solution Process Saturated Solutions and Solubility • Dissolve: solute + solvent → solution. • Crystallization: solution → solute + solvent. • Saturation: crystallization and dissolution are in equilibrium. • Solubility: amount of solute required to form a saturated solution. • Supersaturated: a solution formed when more solute is dissolved than in a saturated solution. Factors Affecting Solubility • • • • • Solute-Solvent Interaction Polar liquids tend to dissolve in polar solvents. “Like Dissolves Like” Miscible liquids: mix in any proportions. Immiscible liquids: do not mix. Intermolecular forces are important: water and ethanol are miscible because the broken hydrogen bonds in both pure liquids are re-established in the mixture. The number of carbon atoms in a chain affect solubility: the more C atoms the less soluble in water. https://sites.duke.edu/apep/module-4-alcohol-and-the-breathalyzer-test/content-ethanolvaporizes-to-a-gas-in-the-lungs/ Prentice Hall © 2003 Chapter 13 Factors Affecting Solubility Solute-Solvent Interaction • The more polar bonds in the molecule, the better it dissolves in a polar solvent, e.g. more -OH groups within a molecule increases solubility in water. • The less polar the molecule the less it dissolves in a polar solvent and the better is dissolves in a non-polar solvent. • Concept of “Like dissolves Like” Factors Affecting Solubility Solute-Solvent Interaction Factors Affecting Solubility Solute-Solvent Interaction Prentice Hall © 2003 Chapter 13 Factors Affecting Solubility Solute-Solvent Interaction • Network solids do not dissolve because the strong intermolecular forces in the solid are not reestablished in any solution. Pressure Effects • Solubility of a gas in a liquid is a function of the pressure of the gas. Factors Affecting Solubility Pressure Effects Chapter 13 Factors Affecting Solubility Pressure Effects – The higher the pressure, the greater the solubility. – The lower the pressure, the fewer molecules of gas are close to the solvent and the lower the solubility. • If Sg is the solubility of a gas, k is a constant, and Pg is the partial pressure of a gas, then Henry’s Law gives: S g = kPg Factors Affecting Solubility Pressure Effects • Carbonated beverages are bottled with a partial pressure of CO2 > 1 atm. • As the bottle is opened, the partial pressure of CO2 decreases and the solubility of CO2 decreases. • Therefore, bubbles of CO2 escape from solution. Factors Affecting Solubility Temperature Effects • As temperature increases, solubility of solids generally (not always) increases, e.g. sugar dissolves better in warm water than cold. • Sometimes, solubility decreases as temperature increases (e.g. Ce2(SO4)3). Factors Affecting Solubility Temperature Effects • Gases get less soluble as temperature increases, e.g. carbonated beverages go flat as they get warm. • Thermal pollution: if lakes get too warm, CO2 and O2 become less soluble and are not available for plants or animals. Prentice Hall © 2003 https://ibiologia.com/fatty-acid-structure/ Chapter 13