Show Menu
Cheatography
  1. Home >
  2. Education >

PChem Unit 3 Cheat Sheet (DRAFT) by

Principles of Chemistry Unit 3.

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Interm­ole­cular forces vs Intram­ole­cular forces

Interm­ole­cular Forces
Between macrom­ole­cules
Intram­ole­cular Forces
happen within

IMFs to explain membranes

Hydrop­hilic heads
in water (polar)
Hydrop­hobic tails
away from water (nonpolar)

Electr­oneg. diff. vs bond polarity -> ions

The larger the electr­one­gat­ivity differ­ence, the more polar the bond
When electr­oneg. greater than 2
bonding e spend most time close to nometals, ionic bond instead of shared e covalent bond

Predicts behavior protein in solvents

Side with most compatible IMFs w/solvent
will be on outside if dissolves (polar)
Oils (hydro­car­bons)
opposite water (nonpolar)

PP polymer to degree cross linking chains

Additives (alter proper­ties)
Substances added to polymeric materials
Cross-­linking
2 or more molecules together with covalent bond or connecting with ionic
Physical properties
highly increased by degree cross-­linking
Low degree cross-­linking
More flexible, more soluble
High degree cross-­linking
more rigid, higher mp, bp

Predict charges Polyatomic ions

Polyatomic ions
Ionic compounds
ions in lattice
Molecular ions (seceral atoms covalently bonded)
OH- NO3- CO3,2-, SO42-, PO43-, NH4+
Charges balance out

Identify monomers to form Polymers

Monomers
building blocks of polymers
Addition formation
link up amide formation combining carboxylic acide + amine = amine to N
Type of polyme­riz­ation
impacts final structure

Ionic compound nomenc­lature

Common Functional groups

Unit cell

Repeating units that build the crystal lattice

Strength + #C influence mixing

A mixture will only mix if it meets atleast one of the two criteria
1.
Mixed version has more config­ura­tions
2.
Mixed version has lower Ep (therm­ody­namics)
Exothermic reactions desired
Loose energy, don't require energy to occur
Temper­ature can impact
Bottom right on PEC diagram

Polari­zab­ility and Molecular Geometry impacts IMFs

Larger
More disper­sion, because more space for IMFs intera­ctions
Distertion from polari­zab­ility (e cloud disterted by external electric field)
causes temporary dipoles that induce dispersion forces.
Polari­zab­ility increases
Dispersion increases

PP. Ionic compounds vs elctro­static intera­ctions

Ionic compounds tend to be solids with high melting and boiling points, becasue ion-ion electr­ostatic forces are strong

Size cat. +an. periodic trends, coulumbs law

Cations
Smaller because they loose elctrongs
Anions
Large because gain electrons
If isoele­ctric ions (all same e config­ura­tion)
greatest protons has greatest charge and lowest melting point because smaller radius because e pulled closer
Coulumb's law
F=q1q2/r2

Dispersion

Dispersion
IMFs that area always present
 
Induced dipoles
 
major contri­butor to IMFs
Relati­onships
Larger
More dispersion
Higher bp and mp
More dispersion
More polari­zable
Stronger dispersion

Hydrogen bonding

Definition
Hydrogen atoms covalently bonded to NOF
These bonds have a large electr­one­gat­ivity difference which creates large bond dipoles and large partial charges.
e defficient hydrogen in one molecule gets close with e rich NOF in another
Stronger electr­ostatic intera­ctions are more likely

Dipole­-Dipole Forces

Only occur in polar molecules
Permanent dipole
Definition
Polar molecules have opposite parellel charges, Opposite partial charges intera­cting with partial charges of other molecules create dipole diploe forces
 

Predic­tions of solubility

Soluble if
charge is less than 4
Large radius
More soluble

Electr­ostatic intera­ctions vs atomic structure

Strucute of ionic compounds maximu­mizes electr­ostatic attraction with overall charge neutrality
Solid close together

Strong, weak electr­olytes

Strong electr­olytes
Soluble, Charges less than 4, atoms move more freely, conducts electr­icity
Weak electr­olytes
Slightly or nonsol­uble, dont conduct electr­icity, charges greater than 4

Charge neutraity -> formula ionic compounds

Charges =0
cross multiply
reduce

Features ionic comp. influence solubility

If product of charges greater than 4
Insoluble
The large the ion
more soluble b/c weaker IMFs

Ionic charge vs period. trend e config.

Electr­one­gat­ivity
Increases to top right
E- nuclear attration
increases to top right
Cations
Smaller that og, b/c loose e-
Anions
Large than o.g, b/c gain e-
Charge ions acquire when they react
determined by e config­uration driven by stability of full outer shell
electrons go from
metal to nonmetal

IMFs to explain protein structure

Protein
Natural polymer by combo of smaller molecules (monomers)
Primary structure
Unique sequence amino acids
Secondary structure
Localized folding proteins
Tertiary
3D strucute of a peptide chain formed by intera­ctions between R-groups

Strength of IMFs explain protein folding

Protein folding is determ­inded by strength of IMFs.
Polar folds
toward water
Interm­ole­cular intera­ctions with H2O and Intram­ole­cular intera­ctions between amino acid residues
folding into structural confir­mation that is most energe­tically stable in the enviro­nment
Intra
specific chain folding
Looks for like places to bond to
Strong stabilizes

Properties by chain length, branching

Chain length and branching impact chain shape and intera­ctions
Longer
More density, more IMFs
Shorter, More branching
less rigid, weaker IMFs, lower density

Functional groups relate to IMFs

Add unique charac­ter­istics to each monomer
Each has distinct IMFs

Common Functional groups

Funct. groups of polymer chains vs intera­ctions

Functional groups impact
how molecules interact with eachother and other suvstances
Functional groups
predict intera­ctions

Structural Formulas and Line Structures

Double bond
Two parellel lines
Carbons
Bends and Ends
Hydrogen
Fulfill octet rule for carbons

Physical P. strength IMFs + molecular structure

Physical properties
Emerge from IMFs among millions of molecules
IMFs arise because of
uneven changing charge
Stronger IMFs
More Energy required to seperate
Physical properties
determined by polarity and polari­zab­ility and possiblity of hydrogen bonding
Physical Properties of carbon based compounds
determined by molecular shape, size and functi­onality

Periodic trends of IMFs

Stronger IMFs
Higher mp and bp
Stronger IMFs
Lower vapor pressure and viscosity
Polari­zab­ility
Tendancy to develope temporary dipoles
Large molecule, Stronger IMFs
more polari­zable

Strength of IMFs

Dispersion
Stronger with larger molecules/ more e-
Increases
Disper­sion, Dipole­-Di­pole, Hydrogen bonding, Ion-Dipole
Stronger IMFs
Higher bp

Types of IMFs Present

All have dispersion forces
Polar
Dipole­-Dipole forces
H+N,O,F
Hydrogen Bonding
Ionic compound + polar molecule
Ion-dipole

Relative Energy Range

Interm­ole­cular intera­ctions weaker than
Covalent bonds
Sharing e is a stronger attrac­tion, more stable higher E because e closer to nucleus