MCAT General Chemistry Review 4

Solution
Homogeneous mixture of two or more compounds in a single phase.
Solvent
Compound which there is more of in a solution
Solute
Compound which there is less of in a solution.
Ideal Solutions
Solutions made of compounds with similar properties.
Ideally dilute solutions

Solute molecules are completely separated by solvent molecules so that they no interaction with one another.

Mole fraction is about one.

Nonideal Solution
Violates properties of both ideal and ideally dilute solutions.
Colloids

Solutions that form with different solvent/solute sizes.

Tyndall Effect: scattering of light through a colloid.

Seperation by coagulation of dialysis (semipermeable membrane).

Ionic compounds are dissolved by…
Polar solvents
Solvation
When ionic compounds are dissolved by polar substances and break apart into their respective cations and anions and they are surrounded by oppositely charged ends of the polar solvent.
Hydration
The process when several water molecules attach to one side of an ionic compound and are able to overcome the strong ionic bond to break the compound apart.
Aqueous Phase
Something that has been hydrated.
Electrolytes
Compounds that form ions in aqueous solutions.
Nitrite

NO2

Nitrate

NO3

Sulfite

SO32-

Sulfate

SO42-

hypochlorite

ClO

chlorite
 ClO2
chlorate

ClO3

perchlorate

ClO4

carbonate

CO32-

bicarbonate

HCO3

phosphate

PO43-

Molarity, M
m=moles of solute/volume of solution
Molality, m
m= moles solute/kg solvent
Mole Fraction, X
X = moles of solute/total moles of all solutes and solvents
mass %
mass solute/total mass solution x 100%
Parts per million
ppm=(mass of solute/total mass solution) x 106
Heat of Solution

Heat given off when bonds are formed.

Negative HoS gives off heat.

Solution formation has positive entropy.

Vapor Pressure

The pressure created by molecules in an open space.

Increases with temperature.

Nonvolatile Solute
a solute with no vapor pressure.

Rault’s Law

Vapor Pressure

PV=XaPa
Volatile Solute
a solute with vapor pressure.
Solubility
Solutes tendancy to dissolve in a solvent.
Precipitation
Solute falling out of solution.
Saturation
When the rate of dissolution and precipitation are equal.
Solubility product, Ksp

The equilibrium constant of a solvation reaction.

Solids and pure liquids are left out.

Ex:

Ba(OH)2(s);;Ba2+(aq) + 2OH-(aq)

Ksp=[Ba2+][F-]2

Lowest Ksp is least soluble, first to precipitate.

Common Ion Effect
Disturbance in the equilibrium because of a common ion in the equilibrium expression.
x

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