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Ways of Expressing Concentration

1. Molarity: Mi.

2. Percent Solutionsa. Percent by volume

i. x 100%b. Percent by mass

i.

x 100%

c. Percent mass over volumei.

x 100%

3. Molality (mol/kg): mi.

4. Mol fractioni.

XA =

*ppm = 1g of solute for 106g solution

Intermolecular Forces and Liquids and Solids

1. Phase a homogenous part of the system incontact with other parts of the system but

separated from them by a well-defined

boundary.

o Solid phase iceo Liquid phase water

2. Intermolecular Forces attractive forcesbetween molecules. Generally much weaker

than intramolecular forces

o Ex. 41 kJ to vaporize 1 mole of watero Measured by:

Boiling point Melting point Hvap Hfus Hsub

3. Intramolecular Forces hold atoms together ina molecule

o Ex. 930 kJ to break all O-H bonds in 1mol of water

Intermolecular Forces

1.

Dipole-Dipole Forces attractive forcesbetween polar molecules

2. Ion-Dipole Forces attractive forces betweenan ion and a polar molecule

3. Dispersion Forces attractive forces that ariseas a result oftemporary dipoles induced in

atoms or molecules; usually increase with molar

mass

a. Polarizabilityi. the ease with which the

electron distribution in theatom or molecule can be

distorted

ii. increases with greater numberof electrons and more diffuse

electron cloud

4. Hydrogen Bond a special dipole-dipoleinteraction between the hydrogen atom in a

polar N-H, O-H, F-H bond and an

electronegative O, N, or F atom.

5. Ionic Bonding attractive forces between ions6. Dipole-Induced Dipole attractive forces

between polar and nonpolar molecules

Properties of Liquids

1. Surface Tension amount of energy required tostretch or increase the surface of a liquid by a

unit area.

(intermolecular forces = surface tension)2. Cohesion the intermolecular attraction

between like molecules

3. Adhesion attraction between unlike molecules4. Capillarity rising of liquid through a narrow

space against the pull of gravity

5. Viscositymeasure of a fluids resistance toflow

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Phase Changes

Equilibrium Vapor Pressure the vaporpressure measured when a dynamic equilibrium

exists between condensation and evaporation

o Dynamic Equilibrium: Rate of condensation= rate of evaporation

Molar heat of Evaporation (Hvap) the energyrequired to vaporize 1 mole of a liquid

a. Clausius-Clapeyron Equation:P = -

P = equilibrium vapor pressure

T = temperature in K

R = gas constant (8.314 J/K-mol)

Boiling Point the temperature at which thevapor pressure of a liquid is equal to the

external pressure

Normal Boiling Point the temperature atwhich a liquid boils when the external pressure

is 1 atm

Critical Temperature (Tc) the temperatureabove which gas cannot be made to liquefy, no

matter how great the applied pressue

Critical Pressure (PC) the minimum pressurethat must be applied to bring about the

liquefaction at the critical temperature

Melting/Freezing Point the temperature atwhich the solid and liquid phases coexist in

equilibrium Molar Heat of Fusion (Hfus) the energy

required to melt 1 mole of a solid substance

Molar Heat of Sublimation (Hsub) the energyrequired to sublime 1 mole of a solid

Phase Diagram summarizes the conditions atwhich a substance exists as a solid, liquid, or gas

Colligative Properties of Solution

- Properties of solution which depends on thenumber of solute particles & not on their

chemical identity

o Vapor Pressure Loweringo Boiling Point Elevation

o Freezing Point Depressiono Osmotic Pressure

1. Vapor Pressure Loweringo The vapor pressure of a solution of

nonvolatile nonelectrolyte is always

lower than the vapor pressure of pure

solid. *vapor pressure: pressure

needed to evaporate

o Raoults Law: the vapor pressure ofsolvent above solution (Psolvent) equals

the mole fraction of solvent in the

solution (Xsolvent) multiplied by the vapor

pressure of the pure element (Psolvent)

Psolvent = (Xsolvent) (Psolvent)

P = (Xsolute) (Psolvent)

2. Boiling Point Elevationo A solution boils at a higher temperature

than the pure solvent

o vapor pressure = higher externalpressure

Tb = (Kb)(m)

Tb = Tb(solution) Tb(solvent)

Tb = boiling point Kb = molal boiling point

elevation constant

o H2O: 0.512 m = molality

3. Freezing Point DepressionTf= (Kf)(m)

Tf = Tf(solvent) Tf(solution)

Tf= freezing point Kf= molal freezing point

constant

o H2O: 1.86 m = molality

4. Osmotic Pressure = MRT

= osmotic pressure M = molarity R = 0.08206 T = temperature in K

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initial state

final state

initial state

final state

Colligative Properties of Electrolyte Solutions

Vant Hoff Factor (i) - One way to measure the extent

to which electrolytes dissolve

- Count the number of ions in the compound

(e.g. K2SO4: i= 3)i =

*applied for electrolytes P, Tb, Tf

Thermochemistry

- Energy flow to and from the system- A system can be:

o Open Change in mass Exchange of heat

o Closed No change in mass Exchange of heat

o Isolated No change in mass No exchange of heat

Internal Energy, E

- The sum of energies for all the particles in thesystem (Kinetic and Potential)

- Immeasurable- in internal energy is immeasurable- E = Efinal Einitial = Eproducts- Ereactants- Change in E of system is always accompanied by

an opposite change in the energy of the

surroundings

Efinal < EinitialEXOTHERMIC

Efinal > Einitial

ENDOTHERMIC

*y axis: Energy

Forms of Energy Transfer

1. Heat (q) energy transferred as a result oftemperature difference

2. Work (w) other form of energy transferTotal charge in systems internal energy is

E = q + w

Energy transfer as heat onlyo Heat flowing out of the system

q is negative E is negative

o Heat flowing into the system q is positive E is positive

Energy transfer as work onlyo Work done by the system

wis negative E is negative

o Work done on a system wis positive E is positive

Law of energy conversion

- the total energy of the universe is constant

(First Law of Thermodynamics)

Euniverse = Esystem + Esurroundings = 0

Units of energy

1 J = 1 kg m2/s2 1 cal = 4.184 J 1 J = 0.2390 cal

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State Functions & the Path of Interdependence of

Energy Change

Energy is a state function, independentfrom the path

o Dependent only on the currentstate of the system, not on the path

the system took to reach the stateo E, P, V are state functionso q and ware not state functions

Enthalpy Change

H, change in enthalpy heat lost or gained

during chemical change or physical

change

- H: exothermic

+H: endothermic

*qp: heat measured at constant pressure

E = q + w

*w: chemical work

1. electrical work2. work done by moving particles3. PV work, expanding gas

a. w= -PVFor reactions at constant pressure

H = E + PV

H = E + PV

E = q + w

= q - PV

qp= E + PV

qp= H

*to get H, get qpqreaction = -qsolution

Comparing E & H

- in most cases, E H for reactions with little

change in PV

Reactions that do not involve gases

1. Neutralization Reaction (V = 0)2. Reaction in which the amount (mol) of

gas does not change

3. Qp is much larger than PV

Some Important Types of Enthalpy Change

1. Hcomb = heat of combustion- when one mole of substance

combines with O2

2. Hf= heat of formation3. Hfus = heat of fusion- when one mole of substance melts

4. Hvap = heat of vaporization

- when one mole of substance vaporizes

Calorimetry

Specific Heat amount of heat required to raise

temperature of 1g of substance by 1C

Heat Capacity amount of heat required to raise

temperature of object by 1C

Specific Heat Capacity

q = mcT

Molar heat capacity (c) the quantity of heat

required to change the temperature of 1 mole

of a substance by 1C

c =

Calorimeter used to measure the heat released or

absorbed by a physical or chemical process

- serves as the surrounding

1. Constant pressure calorimeter(coffee-cup)

2. Constant volume calorimeter (bombcalorimeter)

1. Constant Pressure Calorimetera. Open to the atmosphereb. Determination of specific heatc. Determination of heat of reaction

2. Constant Volume Calorimetera. Given heat capacity of the entire

calorimeter

b. Designed to measure very precisely theheat released in a combustion reaction

Indirect Determination ofH: Hesss Law

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1. H is an extensive property2. H changes sign when a process is

reversed

3. Hesss Law of constant heatsummation

4. BASTA YUNG CANCEL-CANCEL. =))Easiest topic so

Standard Enthalpies of Formation

- standard state of solid of liquid substance is

the pure element or compound at 1atm

pressure & at temperature of interest

Standard Enthalpy of Reaction, Hrxn

- enthalpy change for reaction in which

reactants & products are at standard

states

Hf of formation of a pure element in its most

stable form is zero

+ Hf: formed by endothermic reaction

H = vpHf (product) - vpHf (reactants)