GENERAL CHEMISTRY

122LECTURE NOTES

Introduction

• Syllabus

Be familiar with and keep!!

• Calculators

Must purchase and use TI-30Xa or updated nonprogrammable version !!

• Getting Help

Office Hours or by appointment

Help Sessions

• My Teaching Philosophy

1. It is absolutely necessary to have PP slides in advance. You will also need to takes notes!!!! Problem solving not shown on notes.

2. Help you learn and really understand some fundamentals of chemistry.

3. Help you learn to apply these fundamentals to do problem solving.

4. Coach

5. Athlete Analogy

• Study Tips

1. Amount of time required depends on background and abilities.

2. Practice problems / homework until you can do without text or example.

3. Review / study prior to class.

4. Must understand concepts and be able to apply to problem solving.

5. Get help when needed!!

ORGANIC COMPOUNDS

• Recognition of Structures: (see handout)

Alkanes Ketones

Alkenes Carboxylic Acids

Alkynes Amines

Alcohols Benzene

Ethers Phenyl group

Aldehydes

CHAPTER 11

LIQUIDS, SOLIDS, AND INTERMOLECULAR

FORCES

PROPERTIES OF MATTER

I. KINETIC MOLECULAR THEORY

* All matter is composed of tiny particles (atoms or molecules) in constant motion.

* Increasing temperature increases the motion of the particles.

Can explain properties of matter that we observe on the macroscale on the basis of the behavior of the molecules on the nanoscale.

II. INTERMOLECULAR FORCESForces primarily responsible for differences

between (solids, liquids) and gases.What are they?

1. Attractive forces between molecules2. They are not covalent bonds.3. Much weaker than covalent bonds.

Significant in Understanding Properties of Matter!!!

Covalent Bonds vs. Intermolecular Forces

What are they?

1. London ForcesNoncovalent interaction between all moleculesDue to induced dipole moments

created by movement of electron clouds.

London Dispersion Forces are the only Intermolecular Force between

nonpolar molecules. Factors Affecting Their Strength

Greater Polarizability Stronger LondonDispersion Forces

*** Larger atoms or molecules Stronger Dispersion (London forces) (approximated to atomic or molecular

mass)*** Molecular Shape Stronger London Forces for elongated vs. compact molecules.

Which has strongest London Forces?

a. Ne He Ar

b. F2 Cl2 Br2 I2

Significance?

Which has the highest boiling point?

(Stronger Intermolecular Forces

Higher Melting and Boiling Points)

a. n-Pentane (C5H12) vs. n-Octane (C8H18)

b. n-Octane vs. Isooctane

(see next slide)

2. Dipole-Dipole Forces

Noncovalent interaction between polar molecules or groups.

Attractive force between a partially positive region of one molecule in close proximity to a partially negative region of another molecule

The greater the polarity of a molecule, the stronger the dipole-dipole forces.

Which has strongest Dipole-dipole forces? Why? H-F vs H-Br ??

Examples

1.Which types of molecules commonly have stronger intermolecular forces? Why?

polar vs. nonpolar molecules

2. Which has strongest dipole-dipole forces? propane (C3H8) or acetaldehyde (CH3CHO)

3. Describe / show dipole-dipole interactions for Br-Cl molecules.

3. Hydrogen BondingSpecial dipole-dipole interaction.

Partially positive H atom which is covalently bonded to an electronegative atom (O,N,F) has an attractive force for another electronegative atom (O,N,F).

Greater # H bonds greater intermolecular attractive forces

Hydrogen Bonding is strongest of the threeIntermolecular Forces !!

Examples:

1. Can they hydrogen bond?

1. Water?

2. Methanol (CH3OH)

3. Methane (CH4)

4. Ammonia (NH3)

2. Which forms greatest degree of

hydrogen bonding? ethanol (CH3CH2OH)

or acetic Acid (CH3CO2H)

Properties of Matter Related To Intermolecular Forces

1. Solubility Rule: “Likes Dissolve Likes”

Polar and ionic compounds are soluble in polar solvents.

Nonpolar compounds are soluble in nonpolar solvents.

Is solid KBr more soluble in water or gasoline?

Is vegetable oil more soluble in water or gasoline?

2. Greater Intermolecular Forces Related to Higher Melting and Boiling Points

3. Unusual Properties of Water**Primarily due to ability to form several “H” bonds.

Water thus forms strong intermolecular forces.

1. Low mass, yet liquid at room temperature.

2. High specific heat capacity

3. High heat of vaporization, high boiling point.

4. Ice less dense than liquid water. Ice floats. Why?

PROPERTIES OF LIQUIDS RELATED TO INTERMOLECULAR FORCES

I. VISCOSITYThe resistance of a liquid to flow.

The stronger the intermolecularforces, the greater the viscosity.

Viscosity decreases as temp. increases.

II. SURFACE TENSION * Intermolecular attractions between molecules of a liquid create surface tension.

(unlike a gas)

* Uneveness of the forces on the surface causes the surface of the liquid to contract.

* Surface tension = energy required to increase the surface area by a unit amount.

* Stronger intermolecular forces stronger or higher surface tension.

III. CAPILLARY ACTION * Molecules of liquid can interact with the

molecules of the container.

* Must consider attractive forces between liquid molecules compared to attractive forces between liquid and container.

* What is capillary action?

* What is a meniscus??

IV. VAPOR PRESSURE

* Volatility – tendency of a liquid to vaporize

* Vaporization- when a molecule moves from the liquid phase to the gas (vapor) phase.

Why / how does this happen? (see next Figure)

a. Liquid molecules have varying kinetic energy

b. If kinetic energy of molecules in liquid overcomes intermolecular forces in liquid, they can

escape to gas.

c. Increased temp. increased vaporization Why?

* (Equilibrium) Vapor Pressure

In a closed container the liquid and gas phases of a substance come to dynamic equilibrium.

What does that mean?

The pressure of the gas (vapor) above a liquid at equilibium is called the equilibrium vapor

pressure.

What is creating the pressure?

Higher volatilitymore molecules in gas phasehigher vapor pressure

Example Vapor Pressure ProblemEquilibrium is established between a small quantity of CCl4(l) and its vapor at 400C in a flask having a volume of 285 mL. The total mass of vapor present is 0.480 g. What is the vapor pressure of CCl4, in mm Hg, at 400C?

IV. Boiling Point of Liquid

* Boiling Point- temperature at which the (equilibrium) vapor pressure equals the atmospheric pressure.

* Normal BP – when atmospheric pressure = 1 atm.

Higher intermolecular forces lower vapor pressure higher boiling point

How does size of molecules affect BP?1. Which has highest BP?

Methane (CH4)

Ethane (C2H4)

Propane (C3H6)2. Which has highest BP?

Br2

H2O

How does change in atmospheric pressure affect BP?

PHASE CHANGES OF MATTER

Phase Change Name

SolidLiquid

Liquid Solid

Melting, Fusion

Freezing, Crystallization

Liquid Gas

Gas Liquid

Vaporization

Condensation

Solid Gas

Gas Solid

Sublimation

Deposition

I. PHASE TRANSITIONS

a. Raindrops hit cold metal surface on car

and it becomes covered with ice.

b. Frozen clothes on line dry at below

freezing temperatures (of H2O.)

c. Rubbing alcohol spilled on the palm of

the hand feels cool.

What must be supplied or removed for phase changes?

II. Enthalpy of Phase Transitions Enthalpy (ΔH) = heat energy change under

constant pressure and “temperature” conditions.

If “-” heat produced

If “+” heat required

Liquid ⇌ Gas Δ H vaporization = - ΔHcondensation

H2O (l) H2O (g) ΔHvap = + 40.7 kJ/mol

H2O (g) H2O (l) ΔHcond = - 40.7 kJ/mol

Solid Liquid Gas

Endothermic processes

Gas Liquid Solid

Exothermic processes

** Consider problem solving using ΔH !!

III. Problems Using Enthalpy: Isopropyl alcohol, C3H7OH (60.0 g/mol), is used in rubbing alcohol mixtures. Alcohol on the skin cools by evaporation. How much heat is absorbed by the alcohol if 10.0 g evaporate? The enthalpy of vaporization for isopropyl alcohol is 42.1 kJ/mol.

Note: Problems with changes in temperature of a substance which also includes a phase transition.

How much energy is required to heat 15g of water from –10oC to 60oC?

Δ H fusion = 6.020 kJ/mol

Δ H vaporization = 40.7 kJ/mol

Specific Heat Capacity solid H2O = 2.06 J/goC

Specific Heat Capacity liquid H2O = 4.184 J/goC

Specific Heat Capacity gas H2O = 2.10 J/goC

See next Figure or Figure 11.36 in text

IV. Phase Diagrams * Graphical representation to summarize

conditions (pressure and temperature)under which different states of a substance are stable. See Fig 11.14

* Be familiar with:

a. What the lines represent

b. Identify what states are present at some T and P

c. Terms used

Terms Used:1. Triple Point - P and T where all 3 phases exist in equilibrium.

2. Critical Point – endpoint of line separating liquid and gas. At this point liquid and gas are indistinguishable. Occurs at critical temperature

and critical pressure. Explain

3. Supercritical Fluid - substance that exists above critical temperature and pressure. Has

properties of both liquid and gas. Significance

PHASE DIAGRAM FOR WATER

PHASE DIAGRAM FOR CO2

SOLID STATE INFORMATION

I. Classified as Amorphous or Crystalline Amorphous Solids - a solid that has a disordered

structure. No well defined arrangement of basic units (atoms, molecules, or ions) at nanoscale level. Examples – cement, glass, optical fibers.

Crystalline Solids - a solid that has an ordered structure. Well defined symmetrical arrangement of basic units (atoms, molecules, or ions). Composed of one or more crystals with well defined 3-D structure.

II. Classification of Crystalline Solids

A. Ionic Solid – a solid that consists of positive ions (cations) and negative ions (anions) held together in a lattice by the electrical attraction of the opposite charges (ionic bonds). Very strong bonds. NaCl

B. Molecular Solid – a solid that consists of atoms or molecules held

together by intermolecular forces (London forces, dipole-dipole forces, and hydrogen bonds). Usually involves nonmetals. I2, H2O

C. Atomic Solids1. Metallic Solid – a solid that consists of

positive cores of metal atoms held together

by a surrounding sea of electrons (metallic

bond). Good electrical conductors. Fe

2. Network Solid - a solid that consists of

atoms held together in large networks or

chains by covalent bonds. Network of

nonmetal atoms. Graphite, Diamond

Crystal Structure of Graphite

Forces between layers are

relatively weak.

Hexagons of sp2-hybridized

carbon atoms.

Crystal Structure of Diamond

Three-dimensional network is extremely

strong, rigid.What kind of forces must be overcome to

melt diamond?