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Level 96

Colligative Properties


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solute
A _______ is a substance that dissolves in a solvent to make a solution.
homogeneous mixtures
another name for solutions
solvent
A _______ is a substance that can dissolve other substances.
gaseous solutions
gas or vapors mix in all proportions and are said to be miscible
miscible
2 liquids that dissolve into one another
Immiscible
Conditions where two liquids will not dissolve in one another
liquid solutions
formed by dissolving a gas, liquid, or solid in a liquid solvent (ex: seawater)
solid solutions
ex: dental fillings (liquid mercury in silver); brass (tin in copper)
saturated
a solution that is in equilibrium with respect to a given dissolved substance. (maximum amount of solute under normal conditions)
unsaturated
a solution that is not in equilibrium with respect to a given dissolved substance and in which more of the substance can dissolve. (less than maximum amount of solute under normal conditions)
supersaturated
a solution that contains more dissolver substance than a saturated solution does. normally these solutions are forced into being and are unstable (easily crystallized). holds more then maximum amount of solute under normal conditions. UNSTABLE
Mass Percentage
(mass{grams} of solute/ mass {grams} of solution) times 100
molarity (M)
moles of solute per liter of solution
mole fraction (x)
moles of solute over moles of solution
molality (m)
moles of solute per kg of solvent
process = exothermic
the enthalpy change has a negative sign if step 3 releases more energy than that required by steps 1 and 2
process = endothermic
the enthalpy change has a positive sign if steps 1 and 2 require more energy than is released in step 3
solubility
A measure of how much solute can dissolve in a given solvent at a given temperature.
Factor affecting solubility: structure
polar molecules dissolve in polar solvents and nonpolar dissolve in nonpolar
Factor affecting solubility: temperature
most gases become less soluble with an increase in temperature; in contrast, most solids become more soluble with an increase in temperature
explanation of cold pack:
inside a cold pack is water. in the water is tube containing ammonium-nitrate fertilizer. when the cold pack is hit, the tube breaks open inside and the water mixes with the ammonium-nitrate. this mixture cre…
Factor affecting solubility: pressure
a carbonated soda fizzes when it is first opened because of the release of pressure on solution
Vapor pressure fact
vapor pressure of a solution is lower than vapor pressure of a pure solvent
In order for a molecule to evaporate, it must:
have access to the surface of the solution, and must possess enough energy to escape the attraction of the solute molecules
boiling point occurs when...
V.P. of air = V.P. of H20
Raoult's law
Vapor pressure of a solution is directly proportional to the mole fraction of the solvent present
Isotonic
5%DW - D5W
decrease because molecules are in the way
adding a drug to solution will do what to the tendency to move from a liquid to a gas phase?
Pa0
Pa will only equal this when you have a pure component
real or non-ideal solutions
solutions that do not adhere to Raoult's law are called what?
negative deviation
adhesive forces between A+B are much larger than cohesive forces
positive deviation
adhesive forces between A+B are much less than cohesive forces
real or non-ideal
most solutions in pharmacy are what kind of solutions?
Henry's law
Henry's law states that the number of moles (mol) of a gas dissolved in a liquid at a given temperature is proportional to the partial pressure of the gas.
Raoult's law applies to
solvent in dilute solutions for real liquids
solute and solvent
Raoult's law can apply to both of these in ideal solutions
Positive
Anode (Electrolytic Cell)
drug
vapor pressure for non-electrolytes is reduced by adding what to solution
amount of drug added
depression of non-electrolytes is directly proportional to
Freezing Point
??T fp = Kfp • m • i
osmosis
Movement of a pure solvent through a semipermeable membrane from a solution with a lower solute concentration to one with a higher solute concentration.
osmotic pressure
Drawing power for water, which depends on the number of molecules in the solution.
molality
# of moles of solute / 1000 g of solvent
Freezing Point Depression
The (-) means the temp is going down. We add solutes that will lower the freezing point. Kf=1.86
Van't Hoff
who introduced a correction factor when calculating colligative properties of electrolytes?
is made increasingly dilute
the value of 'i' approaches the number of ions into which the molecule dissociates as the solution
degree of ionization
the value of 'i' depends on
3.4
all drugs that generate 2 particles per molecule will result in a Liso value of
1.9
EN of Si
2.0
Calculate the pH value of this solution to 2.s.f
uni-univalent
3.4
uni-divalent
4.3
di-univalent
4.8
uni-trivalent
5.2
tri-univalent
6.0
7.6
tetraborate electrolytes
A part of its total pressure
A solid or liquid, placed in an enclosed space, evaporates to some extent. This evaporation contributes a new component to the gas and makes up:
Vapor pressure
Force exerted by vapor particles directly above a liquid
Ideal solution
Contains solvent and solute
same
the orbitals in a molecule are not necessarily the _______ as the orbitals in an atom
Real solutions or non-ideal solutions
Systems that deviate from Raoult's Law are called:
Two types of real solutions
Negative deviation and positive deviation
Smaller
Cations are always than their corresponding neutral atom
Solute mixtures
Raoult's law is not applicable to:
Kb
Henry's constant
Varies
Henry's constant _______ between solute components and solvents used.
Ideal
As the solution becomes more and more _______ Henry's constant approaches the value of vapor pressure.
Henry's law applies to:
The solute in dilute solutions for real liquids
Raoult's law applies to:
The solvent in dilute solutions for real liquids.
Raoul's law also applies to:
Both solute and solvent in ideal solutions
directly proportional
mathematical relationship between two variables that change at the same ratio
Vapor pressure is a function of:
the number of molecules of the solute in solution NOT THE NATURE of solution.
The number of molecules in solution
Boiling point, freezing point, and osmotic pressure are functions of:
Van't Hoff and Morse
Two equations for estimating osmotic pressure:
Morse
Osmotic pressure = (Molality)(R)(T)
Morse's Equation
The more precise equation to use for determining osmotic pressure:
Molecular weight
Colligative properties of solutions can be used to estimate:
To determine molecular weight the following values can be used in calculation:
Vapor pressure depression, boiling point elevation, freezing point depression, osmotic pressur elevation, Morse
The Van't Hoff correction factor
(i) Approaches the number of ions into which the molecule dissociates as the solution is made increasingly dilute
(i) depends on:
the degree of ionization of the electrolyte at a particular concentration
A correction factor in the calculation of colligative properties of electrolytes.
For solutions of electrolytes, Van't Hoff found osmotic pressure to be about 2-3 times larger than expected from his equation. Thus he developed
Less than 2
More concentrated electorlyte solutions will have an osmotic pressure value:
An osmotic pressure value of 2:
higher degree of ionization of electrolyte solutions = more dilute
1
For a non-electrolyte solution the Van't Hoff correction factor =
Non-electrolyte solutions are
Dilute, 100% ionized solutions
Liso
A designation given at a concentration of solute that is isotonic with body fluids
Liso can be obtained from:
Freezing point depression of solutions of representative compounds of a given ionic type at a concentration of MB that is isotonic with body fluids.
9
There are _______ values of Liso for the drugs used int he pharmacy
0.52 degrees C
An isotonic solution will always have a delta tf (FP depression) of:
Always positive
Freezing point depression is: