Chemistry Ch. 4

Front 1

Solution

Back 1

-a mixture of two or more compounds in a single phase, solid, liquid or gas.

Front 2

Solvent

Back 2

-the compound of which there is more in a solution
-sometimes when neither compound predominates, both are called solvents

Front 3

Solute

Back 3

-the compound of which there is less in a solution

Front 4

Ideal and ideally dilute solutions

Back 4

-ideal solutions are solutions made form compounds that have similar properties. Can be interchanged within the solution without changing the spatial arrangement of the molecules or the intermolecular attractions
-in an ideally dilute solution, the solute molecules are completely surrounded by solvent molecules so that they have no interaction with each other.

Front 5

Colloid

Back 5

-Particles larger than small molecules form mixtures with solvents called colloids.
-Gravity does not cause the particles to settle out of the mixture over time.
-colloid particles are too small to be extracted by filtration but large enough or charged enough to be separated out by a semipermeable membrane.
-scatter light
-may be attracted or repelled by their dispersion medium
-adding an electrolyte may cause the particles to coagulate.

Front 6

London dispersion forces

Back 6

-Nonpolar molecules are held together by weak intermolecular bonds resulting from instantaneous dipole moments.
-force that

Front 7

Why do 'like disolve like'?

Back 7

-Highly polar molecules are held together by strong intermolecular bonds formed by the attraction between their partially charged ends.
-Non-polar molecules are held together by London dispersion forces
-a polar solute interacts more strongly with a polar solvent by tearing the solvent-solvent bonds apart and forming solvent-solute bonds.
-A non-polar solute does not have enough charge separation to interact effectively with a polar solvent, thus cannot intersperse itself within the solvent.
-A nonpolar solute can tear apart the weak bonds of a non-polar solvent

Front 8

Solvation

Back 8

-process by which ionic compounds dissolve, breaking apart into their respective cations and anions and are surrounded by oppositely charged ends of the polar solvent.

Front 9

Hydration

Back 9

-When several water molecules attach to one side of an ionic compound, they are able to overcome the strong ionic bond, and break apart the compound.
-The molecules then surround the ion.

Front 10

Aqueous phase

Back 10

-A hydrate compound is said to be in an aqueous phase.

Front 11

Nitrite

Back 11

NO2(-)

Front 12

Nitrate

Back 12

NO(-)

Front 13

Sulfite

Back 13

SO3(2-)

Front 14

Sulfate

Back 14

SO4(2-)

Front 15

Hypochlorite

Back 15

ClO(-)

Front 16

Chlorite

Back 16

(ClO2)-

Front 17

Chlorate

Back 17

(ClO3)-

Front 18

Perchlorate

Back 18

(ClO4)-

Front 19

Carbonate

Back 19

(CO3)2-

Front 20

bicarbonate

Back 20

HCO3(-)

Front 21

Phosphate

Back 21

PO4(3-)

Front 22

Electrolyte

Back 22

-a compound that forms ions in aqueous solution

Front 23

Molarity

Back 23

-moles of the compound divided by the volume of the solution

M = Moles of solute/Volume of solution

units: mol/liter

Front 24

Molality

Back 24

m = moles of solute/kilograms of solvent.

units: mol/kg

Front 25

Mole fraction

Back 25

X = moles of solute/total moles of all solute and solvent

no units!

Front 26

Mass percentage

Back 26

mass % = mass of solute/total mass of solution x 100

Front 27

Parts per million

Back 27

-mass of solute/total mass of solution x 10^6

Front 28

Steps of solution formation

Back 28

1. breaking of intermolecular bonds between solute molecules
2. the breaking of intermolecular bonds between solvent molecules
3. the formation of intermolecular bonds between the solvent and the solute molecules

deltaHsol = deltaH1 + deltaH2 + delta H3

-the first two steps in dissolution are endothermic (breaking bonds is endothermic) and the third step is exothermic
-if overall the reaction releases energy, the new intermolecular bonds are more stable than the old.

Front 29

Heat of solution

Back 29

-A negative heat of solution results in stronger intermolecular bonds
-A positive heat of solution results in weaker intermolecular bonds.
-generally, the formation of a solution involves an increase in entropy, so solution formation has a positive entropy

Front 30

Vapor pressure

Back 30

-Some molecules at the surface of a liquid have enough KE to break free of the intermolecular bonds that hold them together in the liquid.
-When the rate of molecules leaving a liquid equals the rate of molecules entering a liquid, equilibrium has been established.
-The pressure created by the molecules in the open space is the vapor pressure.
-related to KE of molecules, a function of temperature.

Front 31

vapor pressure: melting point and boiling point.

Back 31

-an endothermic process
-when vapor pressure equals local atmospheric pressure, a compound boils.
-Melting occurs when the vapor pressure of the solid phase equals the vapor pressure of the liquid phase.

Front 32

Nonvolatile solute

Back 32

-a solute with no vapor pressure.
-when added to a liquid, some of the solute molecules will reach the surface of the solution, and reduce the amount of surface area available for the liquid molecules.
-the number of molecules breaking free is decreased while the surface area of the solution and the volume remains the same.

Front 33

Raoult's law (when a nonvolatile solute is added)

Back 33

-the vapor pressure of solution P is proportional to the mole fraction of the liquid and the vapor pressure of the pure liquid Pa when a nonvolatile solute is added.

Pv = XaPa

Pa = vapor pressure of pure liquid
Xa= mole fraction of pure liquid
Pv= final vapor pressure

Front 34

Raoult's law (when a Volatile solute is added)

Back 34

-a solute with vapor pressure
-also competes for surface area of a liquid
-will escape from surface and contribute to vapor pressure
-exhilbits modified Raoult's law:

Pv = XaPa + XbPb

Front 35

Solubility

Back 35

-a solute's tendency to dissolve in a solvent.
-typically the solute is a salt and the solvent is often water.

Front 36

Precipitation

Back 36

-the reaction reverse to dissolving a salt.
-takes place initially at a slower rate than dissolution.

Front 37

Saturation

Back 37

-as salt dissolves and the concentration of salt builds, the rate of dissolution and precipitation equilibrate.
-When the rate of dissolution and the rate of precipitation are equal, the solution is said to be saturated
-the concentration of dissolved salt has reached a maximum in a saturated solution.

Front 38

Solubility product Ksp

Back 38

-The equilibrium of a solvation reaction has its own equilibrium constant.
-SAME RULES APPLY AS WITH OTHER EQUILIBRIUM CONSTANTS!!
-remember that the solubility product is not the same as solubility; it is a constant and can be found in a reference book.
-changes only with temperature; the solubility depends on temp and the ions in solution.

Front 39

Crystalization of salts

Back 39

-for most salts, an exothermic reaction.

Front 40

Spectator ions

Back 40

-Ions that are not included in an equilibrium expression and thus have no effect on the equilibrium.

Front 41

The common ion effect

Back 41

-ions that DO effect the equilibrium because they are involved in the equilibrium expession.
-the addition of a common ion will shift the equilibrium in the direction that tends to reduce the conc. of that ion (By Le Chatalier principle).
-a common ion added to a saturated solution will shift the equillibrium increasing precipitate. It does not effect Ksp.
-a common ion added to a solution that is not saturated will NOT shift the equilibrium because in an unsaturated solution, there is no equilibrium shift.

Front 42

Effects on solubility by pressure

Back 42

-Pressure on solids and liquids has little effect on solubility
-Pressure has a big effect on gas solubility.

Front 43

Raoult's law vs. Henry's law

Back 43

-both equations show that the concentration of a gas in solution is proportional to the vapor partial pressure of the the gas above the solution.
-Raoult's law is more accurate when looking at the vapor partial pressure of a solvent with high concentration.
-Henry's law is more accurate when looking at the vapor partial pressure of a volatile solute where the solute has a low concentration.
-In an ideally dilute solution, the solvent obeys Raoult's law and the solute obeys Henry's law.
-when the solvent concentration is high, each solvent molecule is surrounded by other solvent molecules, so it behaves more like a pure solvent. The solvent vapor pressure is proportional to its vapor pressure as a pure liquid-Raoult's law.
-When the volatile solute concentration is low, each molecule is surrounded by solvent molecules creating a deviation from the behavior of a pure volatile solvent. This vapor partial pressure is not proportional to its pressure as a pure substance-Henrys law works.

Front 44

Henry's law

Back 44

-demonstrates that the solubility of a gas is proportional to its vapor partial pressure.