Definitons to cover~

Enthalphy of hydration: for an ionic compound, this is the enthalphy change that corresponds to taking the separated ions in the gas phase and transforming them to the hydrated ions in solution

Henry's Law: the solubility of a gas in a liquid is proportional to the partial pressure of a the gas
S(g)=K(h) x P(g)

Raoult's Law- the vapor pressure exerted by the vapor of the solvent in a solution is equal to the mole fraction of the solvent in the solution multiplied by the vapor pressure of the pure solvent
P(solvent)= X(solvent) x P0(solvent)


Types of Intermolecular Forces:

London Forces = (aka van der Waals dispersion forces, instantaneous dipoles, induced dipoles, etc.); very weak attractive forces because of the unequal distribution of electrons around the atom
Dipole-Dipole Forces = attraction between the partial positive end of one dipole and the partial negative end of another dipolar molecule; can exists between molecules of the same substance or different substance
Hydrogen Bonding = very strong dipole-diple attractive forces observed exclusively in compounds that have an F, N, or O bonded directly to an H atom

(Decreasing intermolecular forces strengths)
-Ion-dipole>
-Dipole-dipole attraction>
-Dipole-induced dipole interaction>
-Induced dipole-induced-dipole force = London dispersion force


The process of inducing a dipole is called polarization.

Hydrogen Bonding:The attractive force between molecule having: N-H, O-H, and F-H bonds that have large molar masses


Surface tension = occurs when there is an increase in the attractive forces between molecules at the sufacce of a liquid compared to the forces between molecules in the center or bulk of the liquid

evaporation = requires the kinetic energy of the gas molecules to overcome the intermolecular forces

Freezing Point Depression: There is more atoms of pure solvent going from solid to liquid than from liquid to solid
ΔTfp measured = Kfp x molality of solute x i

Boiling point- when vapor pressure = external pressure
Normal boiling point- when external pressure = 760 mm Hg

Critical point- at critical temperature and critical pressure; when substance becomes super-critical fluid
Super-critical fluid- density like liquid; viscosity like gas

Triple point- when all three phrases coexist at equilibrium


Molarity (M) = amount of solute (mol)/ volume of solution (L)
Molality (m) = amount of solute (mol)/ mass of solvent (kg)
Mole fraction (Xa)= # moles of A/ total # moles
Weight percent (w/w%)= mass of A/ total mass x 100
Weight/volume % (w/v%)= mass of A/total volume x 100
Parts per million (ppm) = mg substance/ 1L of solution

Colligative properties- depend only on number of solute/solvent particles; substance itself not important

Miscible- 2 liquids mix to an appreciable extent to form a solution.
Immiscible- liquids do not mix; they exist in contact with each other forming layers



TRENDS
Boiling Point:
1) as the IMF increase, the boiling point also increases.
2) the types of intermolecular forces that a compound has are more influential than the molecular weight of the molecule. For example, the boiling point for a substance with hydrogen bonds is much higher than a substance with a higher molecular weight but no hydrogen bonds.

Viscosity
1) increases as the molecular weight of the substance increases
2) increases as the IMF of the substance increase
3) similar to boiling point, the type of intermolecular forces ( such as hydrogen bonds) are more influential that the molecular weight in determining the viscosity

Evaporation rate:
1) as molecular weight increases, the number of electron shells also increase. The electrons are more polar-izable and thus experience stronger IMF. This decreases the rate.
2) increase IMF strength = decrease in evaporation rate.


Freezing/melting point:determined by the type of IMF-----high IMF=high melting point
1) substances with induced-induced = lowest melting points due to low IMF (does not require lots of energy to break london dispersion forces)
*** molecular weight determines melting point among induced-induced-----higher weight=higher melting point (more energy required because higher molecular weight = greater IMF due to polar-izable electron shells)
2) substances with dipole-dipole (hydrogen bonding) = intermediate melting points
3) substances with ion-ion = highest melting points due to the high IMF (requires lots of energy to break ionic bonds)





Changing Vapor Pressure what happens when something is dissolved in solvent?
1) less solvent physically present at the surface of the substance
2) different set of attractive forces
EQUALS DECREASED VAPOR PRESSURE ********vapor pressure of any substance with a nonvolatile solute compared to pure substance is lower

Pressure of solvent = (mole fraction of solvent)(pressure of pure solvent) ALSO KNOWN AS RAOULT'S LAW

**assumes substance is ideal----if attraction between solute and solvent is stronger than attraction between solvent and solvent = actual vapor pressure will be lower than calculated

Boiling Point Elevation
delta T = K (molality solvent) ( number of ions)

Freezing Point Depression
delta T = K (molality solvent) ( number of ions)



phase diagrams:

negatively sloping line for water's solid/liquid equilibrium curve because liquid water is denser than ice
for most other compounds, the slope is positive

:: IN DILUTE AQUEOUS SOLUTIONS, MOLARITY = MOLALITY (approximately) ::