CHEM Chapter 13 Exam 2
colligative properties
properties of a solution that depend only on the number of particles dissolved in it, not the properties of the particles themselves. The main ones are boiling point elevation and freezing point depression.
osmotic pressure
pressure that must be applied to prevent osmotic movement (osmosis) across a selectively semi-permeable membrane
Vapor Pressures of Solutions Containing a Volatile (Non-electrolyte) Solute
-contain both a volatile solvent and solute so they both contribute to the overall vapor pressure -IDEAL SOLUTION
Colligative Properties and Medical Solutions
-healthcare workers often administer solutions to patients -osmotic pressure is controlled to get the desired affect EX: isotonic, hyper-osmotic, and hyposmotic solutions
nonvolatile solute
-lowers vapor pressure of solute which causes: -freezing point to decrease -boiling point to INCREASE
colligative properties
-vapor pressure lowering -boiling point elevation -freezing point depression -osmotic pressure
osmosis
Diffusion of water through a selectively permeable membrane -is the flow of solvent from a solution of lower solute concentration to one of higher solute concentration -draws pure solvent towards concentrated solutions (causing more dilute)
Hyperosmotic Solution (Hypertonic)
Has a greater concentration of solute compared to the reference solution (body fluids). A red blood cell shrinks.
Notice the similarity between osmosis and vapor pressure lowering.
In both cases, as a solution becomes concentrated, it develops a tendency to draw pure solvent to itself. In the case of vapor pressure lowering, the pure solvent is drawn from the gas state. In the case of osmosis, the pure solvent is drawn from the liquid state. In both cases, the solution becomes more dilute as it draws the pure solvent to itself—nature's tendency to mix is powerful.
Strong Electrolytes and Vapor Pressure
Just as the freezing point depression of a solution containing an electrolyte solute is greater than that of a solution containing the same concentration of a nonelectrolyte solute, so the vapor pressure lowering is greater (for the same reasons) -vapor pressure for a NaCl solution, for example, decreases about twice as much as it does for a nonelectrolyte solution of the same concentration
nonvolatile solute
One which will not enter the vapor phase (extremely hard to vaporize)
What is the effect of a nonvolatile nonelectrolyte solute on the vapor pressure of the liquid into which it dissolves?
The basic answer is that the vapor pressure of the solution is lower than the vapor pressure of the pure solvent. The vapor pressure of a solution is lower than that of the pure solvent because of nature's tendency toward mixing (toward greater entropy)
electrolyte dissociation
When 1 mol of a nonelectrolyte dissolves in water, it forms 1 mol of dissolved particles. When 1 mol of an electrolyte dissolves in water, however, it normally forms more than 1 mol of dissolved particles EX: 1 mol NaCl dissolves in water it forms 1 mol of Na+ ion and 1 mol of Cl- ion total of 2 moles of NaCl produced (electrolyte) -The colligative properties of electrolyte solutions reflect this higher concentration of dissolved particles
Semi-permeable membrane
a membrane (as a cell membrane) that allows some molecule to pass through but not others
Vapor pressure ordering
by placing a beaker of concentrated solution of a nonvolatile solute and a beaker of the pure solvent in a sealed container -level of the pure solvent will drop, and the level of the solution will rise as molecules vaporize out of the pure solvent and condense into the solution, causing concentrated solution to be LESS concentrated
Colligative Properties of Strong Electrolyte Solutions
freezing point depression of a 0.10-m sodium chloride solution is nearly twice this large. Why? Because 1 mol of sodium chloride dissociates into nearly 2 mol of ions in solution. The ratio of moles of particles in solution to moles of formula units dissolved is called the van't Hoff factor (i)
hyposmotic solution
has a lower osmotic pressure than the solution inside the cell - as a result there is a net flow of water into the cell, causing it to swell.
vapor pressure of a liquid
is the pressure of the gas above the liquid when the two are in dynamic equilibrium (that is, when the rate of vaporization equals the rate of condensation)
isosmotic (isotonic) solution
solution in which the solute concentration and the water concentration on both the inside and outside of the cell membrane is equal; the cell remains the same shape and dynamic equilibrium is present here but the net change is zero -most common -When intravenous fluids are given in a hospital, the majority of the fluid is usually an isosmotic saline solution—a solution containing 0.9 g NaCl per 100 mL of solution
freezing point depression
the difference in temperature between the freezing point of a solution and the freezing point of the pure solvent -The freezing point of a solution containing a nonvolatile solute is lower than the freezing point of the pure solvent. For example, antifreeze, used to prevent the freezing of engine blocks in cold climates, is an aqueous solution of ethylene glycol (C2H6O2)(C2H6O2). The more concentrated the solution, the lower the freezing point becomes.
van't Hoff factor
the ratio of moles of particles in solution to moles of solute dissolved
nonideal solution
the solute-solvent interactions are either stronger or weaker than the solvent-solvent interactions -does not obey Raoult's law -if solute-solvent interactions are STRONGER than the solvent-solvent interactions, then the solute tends to allow LESS vaporization, therefore is LOWER than predicted Raoult's law -if solute-solvent interactions are WEAKER than the solvent-solvent interactions, then the solute tends to allow MORE vaporization than would occur with just the solvent. If the solution is not dilute, the effect is significant and the vapor pressure of the solution is greater than predicted by Raoult's law
boiling point elevation
the temperature difference between a solution's boiling point and a pure solvent's boiling point
