MOLECULES AND SOLUTIONS Flashcards
WHAT ARE COLLIGATIVE PROPERTIES?
-properties of solutions that depend on the number of particles in a volume of solvent (the concentration) (osmolarity) and not on the mass or identity of the solute particles. Colligative properties are also affected by temperature.
WHAT DO NON-COLLIGATIVE PROPERTIES DEPEND ON?
-identity of the dissolved species and the solvent
WHAT HAPPENS WHEN A SOLUTIONS OSMOLARITY INCREASES?
-osmotic pressure increase
-vapor pressure decrease
-freezing point decrease
-boiling point decrease
WHAT IS RAOULTS LAW? (IDEAL SOLUTIONS)
when a non-volatile solute is added to a liquid to from a solution, the vapor pressure above that solution decreases
-vapor pressure of a solution (p) equals the mole fraction of the solvent multiplied by the vapor pressure of the pure solvent (p0)
-if a pure solute that has 0 vapor pressure is dissolved in a solvent, the vapor pressure of the final solution will be lower than that of the pure solvent
WHAT IS OSMOSIS?
-flow of solvent molecules penetrates a semipermeable membrane and stops the flow of solute molecules only
-when a solution and pure solvent are placed either side of a semipermeable membrane, it is found that more solvent molecules flow out of the pure solvent side of the membrane than solvent flows into the pure solvent from the solution side of the membrane
-this flow of solvent from pure solvent side makes the volume rise
-large height difference between the 2 sides causes net flow to cease due to extra pressure of chamber = osmotic pressure
-more molecules flow from solvent to solution side
WHAT IS THE BOILING POINT OF A LIQUID?
-the temperature at which the vapor pressure of that liquid equals the atmospheric pressure
-unit used is molality
EG: For a solution, the vapor pressure of the solvent is lower at any given temperature. Therefore, a higher temperature is required to boil the solution than the pure solvent.
WHAT DOES OSMOTIC PRESSURE DEPEND ON?
-concentration and temperature
p = M R T
WHAT IS AN ISOTONIC SOLUTION?
-equal solute concentration in
external and internal liquid
WHAT IS A HYPERTONIC SOLUTION?
-higher concentration of dissolved substances in external than in internal liquid
(cells are shrinking)
WHAT IS A HYPOTONIC SOLUTION?
-lower concentration of dissolved substances in external than in internal liquid
(cells are swelling and bursting)
(because the solvent goes into the cell).
WHAT IS COHESION?
-intrinsic property of a substance that
is caused by the shape and structure of its molecules which makes the distribution of orbiting electrons irregular when molecules get close to each other creating electrical attraction that can maintain a macroscopic structure such as a (water drop)
WHAT IS A COHESIVE FORCE / ATTRACTION?
-ability of molecules to stick together due to mutual attraction
WHAT IS SURFACE TENSION?
-a measurement of the cohesive energy
present at an interface
-liquid molecules are attracted to each other
-interactions of a molecule in the bulk of a liquid are balanced by an equal attractive force in all directions
-molecules on surface experience an imbalance of forces as there are attractive forces below them but none above them
-thin layer of molecules is formed at the free surface as molecules are being pulled down and trying to minimize number of molecules at surface
-responsible for shape of liquid droplets
WHAT IS THE CONSEQUENCE OF HAVING A HIGHER OSMOLARITY?
solution with higher osmolarity remains liquid over a larger range of temperatures compared to a solution with lower osmolarity
WHAT IS THE RESULT OF LOWER VAPOR PRESSURE?
it is proportional to the molar concentration of the solute (Raoults law)
WHAT IS THE FREZING POINT DEPRESSION?
addition of a non-volatile solute to a solution lowers the freezing point of the solution relative to the pure solvent
-freezing point depressed due to vapor pressure lowering
-sign of change in freezing point is negative as it is less than that of the pure solvent
-measured in molality
-a lower temperature is required to freeze a liquid
