General Chemistry 2: Ch 11, 12, 13 for Exam

What are the 5 types of intermolecular forces?

Ion-Ion

Ion-Dipole

Dipole-Dipole

Hydrogen

London Dispersion

Ion-Ion IMF

occur between ionic compounds

NaCl, Al2O3

500kJ/mole to overcome these IMF

Ion-Dipole IMF

occur between an ionic compound and polar molecules

aqueous compounds

10-50 kJ/mole

Dipole-Dipole IMF

occur between polar molecules

interact because of unevenness of where electrons are in the molecule

3-4 kJ/mole

Hydrogen IMF

dipole-dipole bond for hydrogen bonding to O,N,F

10-40 kJ/mole

London Dispersion IMF

All molecules, ions, atoms, etc. have dispersion forces. These are the weakest forces.

Unevenness at one instant

1-10 kJ/mole

What are the strongest IMF?

ion-ion IMF

What are the weakest IMF?

London dispersion forces

How is boiling point related to intermolecular forces?

The higher the IMF, the higher the boiling point.

How is melting point related to intermolecular forces?

The higher the IMF, the higher the melting point.

Viscosity

for a liquid, this is its resistance to flow

How is viscosity related to intermolecular forces?

The higher the intermolecular forces, the higher the viscosity.

Surface Tension

how difficult it is for a liquid to spread out

How is surface tension related to intermolecular forces?

The higher the intermolecular forces, the higher the surface tension.

Sublimation

A change from a solid directly to a gas

Deposition

A change from a gas directly to a solid

Vaporization

A change from a liquid to a gas

Condensation

A change from a gas to a liquid

Fusion

A change from a solid to a liquid

Freezing

A change from a liquid to a solid

Which value of ΔH is favorable?

ΔH<0

ΔH is negative

exothermic

Which value of ΔH is unfavorable?

ΔH>0

ΔH is positive

endothermic

Which value of ΔS is favorable?

ΔS>0

ΔS is positive

increasing randomness

Which value of ΔS is unfavorable?

ΔS<0

ΔS is negative

decreasing randomness

What is the sign on ΔG if a process is spontaneous?

ΔG<0

ΔG is negative

What is the sign on ΔG if a process is nonspontaneous?

ΔG>0

ΔG is positive

How many intermolecular forces must be broken when there is a phase change from a liquid to a gas?

~85% of IMF

What is the relationship between evaporation and intermolecular forces?

The lower the IMF, the easier it is to evaporate. The higher the IMF, the harder it is to evaporate.

Vapor Pressure

Gas that is trapped in a container exerts a pressure; this is the vapor pressure.

What is the relationship between vapor pressure and intermolecular forces?

The higher the IMF, the lower the vapor pressure.

Clausius-Clapeyron Equation

ln (P1/P2) = (ΔHvap/R) (1/T2 - 1/T1)

Convert 1 atm to mmHg, torr, psi, and Pa.

1 atm = 760 mmHg = 760 torr = 14.7 psi = 101325 Pa

Amorphous Solids

no long range pattern or repeating structure/order in 3D

ex. glass

Crystalline Solids

pattern, repeating structure in 3D

flat faces, sharp edges

Name the four categories of crystalline solids.

ionic, molecular, covalent network, metallic

Ionic Solids

high melting points

brittle material that cracks between ions

Name examples of ionic solids.

NaCl, CaCl2, Al2O3

Molecular Solids

small molecules in solid state

hydrogen bonds hold small molecules in a pattern

generally low melting points

Name examples of molecular solids.

ice, dry ice, sugar

(H2O, CO2, C6H12O6)

Covalent Network Solids

3D or 2D network of all covalent bonds

very strong material

very high melting point

Name examples of covalent network solids.

diamond and graphite

(both are solid carbon)

Metallic Solids

metals in elemental state; properties vary

Name examples of metallic solids.

Na (s) soft metal

W (s) strong metal

What is X-ray crystallography used for?

This is used to create images of atoms in crystals.

Simple Cubic Packing

Layers are stacked directly on top of each other.

Coordination Number

the number of nearest neighbor atoms that surround any other given atom of a solid structure

What is the coordination number of a simple cubic packing?

6

Body-Centered Cubic Packing

Layers are stacked on top of one another, but are skewed and form a zigzag pattern.

What is the coordination number of a body-centered cubic packing?

8

Hexagonal Closest-Packed

One layer of 3 atoms is stacked between 2 layers of 7 atoms.

(1 bee for 2 flowers)

What is the coordination number of a hexagonal closest-packed?

12

Cubic Closest-Packed

Two layers of 3 atoms each are stacked between 2 layers of 7 atoms.

What is the coordination number of a cubic closest-packed?

12

Which packing is the most efficient, and which is the least efficient?

Most: hexagonal closest-packed and cubic closest-packed

Least: simple cubic packing

Unit Cell

smallest repeating unit in the crystal

SCC

Simple Cubic Unit Cell

BCC

Body-Centered Cubic Unit Cell

FCC

Face Centered Cubic Unit Cell

How many atoms are in a simple cubic unit cell?

1

How many atoms are in a body-centered cubic cell?

2

How many atoms are in a face-centered cubic cell?

4

Which unit cell is the least efficient?

Simple Cubic Unit Cell (SCC)

Which unit cell is the most efficient?

Face Centered Cubic Unit Cell (FCC)

Name examples of covalent network solids.

diamond, graphite (solid carbon)

silica (SiO2)

glass

Amorphous

no time for pattern to form

Name an example of a molecular solid.

Solid Water (Ice)

Phase Diagram

a pressure vs. temperature graph that allows us to identify which phase of matter a substance is in

Is each phase diagram the same?

No; phase diagrams are different for each substance.

Supercritical Fluid

has properties of both a gas and a liquid at the same time

Critical Point

the point above which there exists a supercritical fluid

Triple Point

all 3 phases meet; all are present; all are in equilibrium

Where is melting point located on a phase diagram?

The solid-liquid line

Where is boiling point located on a phase diagram?

The liquid-gas curve

Pure Substance

elements and compounds

Name examples of pure substances.

Na (s)

Cl2 (g)

NaCl (s)

Can an aqueous compound be pure?

No, because you must add water to make an aqueous substance.

Mixture

physical combination of substances

Name examples of a mixture.

NaCl (aq)

air

sports drink

Homogeneous Mixture

a mixture that is evenly mixed; uniform mixture

Name an example of a homogeneous mixture.

air

sports drink

gasoline

Heterogeneous Mixture

a mixture that is not evenly mixed

Name an example of a heterogeneous mixture.

muddy water

chunky salsa

Solution

atom scale mixing

Colloid

cloudy mixture

Suspension

a mixture that you must shake to make uniform

Solute

component in solution that is present in lesser amount by moles

Solvent

component in solution that is present in greater amount by moles

Dissolution

dissolving

How do you write a dissolution equation?

Solute <--> Dissolved ions

solvent is written above arrow

What does "like dissolves like" mean?

Substances with a similar structure and similar intermolecular forces will mix.

Does spontaneous dissolution mix?

yes

Gibbs Free Energy is less than 0 (negative)

Does nonspontaneous dissolution mix?

no

Gibbs Free Energy is greater than 0 (positive)

What is it called when dissolution releases heat?

exothermic

ex. hot pack

What is it called when dissolution requires heat?

endothermic

ex. cold pack

What can drive dissolution?

ΔS (entropy; randomness)

Molarity

moles solute per liter of solution

M/L

Molality

moles solute per kilogram of solvent

m

Mole Fraction

moles of one component/total moles

X

Mass Percent

(mass of one component/total mass) * 100%

%

Parts Per Million (PPM)

(grams solute/total grams) * 10^6