溶液稀释英文版的教学课件 CHAPTER 2.ppt

Chapter 2 Colligative Properties of Dilute Solution 2.1 Solubility NaCl (s) + H2O Na+(aq) + Cl-(aq) 2.1.2 Unsaturated solution A solution not in equilibrium with respect to a given dissolved substance and in which more of the substance can dissolve. 2.2 Vapor Pressure Lowering of A Solution 2.2.1 Vapor-pressure Essential 1. p : Its unit is Pa or kPa. 2.2.2 Vapor-pressure lowering Water Membrane Glucose solution Funnel Π An experiment in osmosis Water passes through the membrane into the glucose solution in the inverted funnel, the liquid level rises in the stem of the funnel until the downward pressure exerted by the solution above the membrane eventually stops the upward flow of water. pure solvent solution net transform of solvent osmotic pressureΠ 2.3.1.2 Osmotic pressure Osmotic pressure is defined as the pressure that must be applied to a solution to prevent any net transfer of pure solvent into it through a semipermeable membrane. The osmotic pressure Π of a solution is related to the molarity of solution, c, (van’t Hoff law) : or ΠV = nRT Π = bRT Here R is the gas constant and T is the absolute temperature. There is similarity between this equation for osmotic pressure and the equation for an ideal gas. * Solubility Boiling-point elevation and freezing-point depression Vapor pressure and Vapor pressure lowering of solution Osmosis Solubility: The solubility is defined as the amount that dissolves in a given quantity of water at a given temperature to give a saturated solution. 2.1.1 Saturated solution State: A solution is in dynamic equilibrium with respect dissolved substance. A dynamic equilibrium is reached in which the rate at which ions leave the crystals equals the rate at which ions return to the crystals. 2.1.3 Supersaturated solution A solution that contains more dissolved substance than a saturated solution does. H2O (l)