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GenChem I (CHEM 121) Mega Review Cheat Sheet (DRAFT) by

General Chemistry 121 Class

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

UNIT 1 -- Concepts!

Proving atoms exist
integer ratios (= represent units of mass= atoms)
Law of conser­vation of mass
atoms/are not created nor destroyed only rearranged
Atomic Molecular Theory
All matter is made up of atoms
Elements can't be decomposed into simpler substances , composed of identical atoms, all elements are defined = elements are composed of atoms
Compounds are chemical substances of elements
 
#s and masses of atoms are conserved in a chemical RXN
Compounds are composed of molecules
Atoms of the same element are identical (=iden­tical mass)
All atoms of a single element have the same charac­ter­istic mass.
Each compound consists of identical molecules, which are small, identical particles formed of atoms combined in simple whole number ratios.
The number and masses of these atoms do not change during a chemical transf­orm­ation. Each element is composed of very small, identical particles called atoms.
Each small atom is surrounded by molecules, which allow bonds to form between neighb­oring atoms.
 
Law of definite Propor­tions (aka LAw of Constant Compos­itions)
elements combine in definite propor­tions by mass to make a certain compound
compound composed of fixed ratio of elements by mass
NO INTEGERS
 
Same compund do not compare different compounds
Law of Multiple Propor­tions
compare multiple compounds made of the same elements if we fix the mass of one element, the other elements' masses across those compounds will be related in a simple integer ratio
must include examples where a specific elemen­t/atom bonds to the same element with different simple integer ratios
INTEGERS
Law of Combining Volumes
At fixed temp and pressure gases combine in simple integer ratios by volume
Avogadro's Law= At a fixed Temp and Presure equal volumes of gases contain equal #s of particles
Diatomic particle : H2 O2 N2 F2 Cl2 Br2 I2
 
Ruther­fords's gold foil experiment
alpha particles shot through a thin gold foil sheet
 
most went straight through = atoms are mostly made of empty space
some slightly deflected= positively charged nucleus
very few bounced back=
Mosely's Xray frequency data
sqrt of frequency is prport­ional to atmoic number
= atomic number measures # protons since

Unit 1 -- Concepts!!

Emperical Formula
simplify ratios??
P4O10=P2O5
Molecular Formula
as is no simpli­fic­ation
Determ­ining moles
M=n/V
where M = Molarity
n = moles (of solute)
V = volume in liters (in solution)

Unit 2 -- Concepts!

Ruther­­fo­rds's gold foil experiment
alpha particles shot through a thin gold foil sheet
most alpha particels went straight through = atoms are mostly made of empty space
some slightly deflected= positively charged nucleus
very few bounced back=n­ucleus is much more massice than alpha particle and really small in position
nuclei are tiny positively charged small and massive
Mosely's Xray frequency data
sqrt of frequency is prport­­ional to atmoic number = atomic number measures # protons since
integer units - counting something = protons
courelated mass
Ionization Energy
minimum amount of energy required to remove an electron {{IE felt relative to specific electron}}
COULOMBS LAW
V(r)=(q1 * q2)/r
   
V(r) is potential energy
negative because opposite charges attract
Positive when salike chgs repel
 
Periodic trend:
left to right ->
charges increase PE

top to bottom: radius increases lowering PE
decreasing IE

Ionization Energy Graph

Unit 2 -- Concepts!

Ionization Energy (con't)
electron electron repulsion decreases ionization energy of electron
Successive IE
large drop indicates new shell e- must be removed from
Photoe­lectric effect
E=hv
where v is frequency and h is Planck's constant
c=lambda* frequency
lambda is frequency
E = (hc)/λ
 
Planck's constant (h)=
speed of light (c)=
 
Rydberg's equation :
Rydberg's constant: 1.097x10-7

Photoe­lectric effect graphs

graph relati­onships

More intense light above threshold frequency produces more electrons, greater current
More intense light above threshold frequency does not produce electrons with greater kinetic energy
When intensity is fixed:­pre­sence of threshold frequency implies relati­onship between frequency and energy – if light is above frequency threshold, the current remains fixed
Kinetic energy of electrons increases when frequency is increased – simple linear relati­onship
§ Summary of experi­mental results: light which has suffic­iently high frequency will eject electrons whether the intensity is low or high–
increasing intensity gives more electrons but not more energetic electrons–
increasing frequency gives more energetic electrons but not more of them

Unit 2 -- Concepts!

frequency of light = color of light and amount of energy carried
intensity of light = number of e-
KE of electron = increases as frequency increases and not affected by intensity
current = affected by intensity (increase current there is an increase intensity)
unaffected by chnage in frequency
must reach threshold frequency of no electrons will be emitted

Unit 2 -- Concepts!

Photo emmision
electrons jump down energy levels emmit light
light absorbed when electrons jump up (get excited)
specif­ic f­req­­uencies of light emitted because between specific energy levels and energy is quantized *
quantum numbers
n= size
1s, 2p 3d
l= shape
1s, 2p, 3d
0 to n-1
m(l) = orientation
(ex: 2p-x, 2p-y, 3d-xy)
m(s) = spin + 1/2 -1/2
Range: -l to +l
Rydberg equation
n=shell n1= 1st energy shell n2= second enrgy shell mn
use to calculate Energy emitted when e- moves between shells
 
(if E(light) fixed)
E(ligh­t)=hv = IE(e-)+IE(e-)
Visisble light range
~400-750 ish
Ultrav­iolet - lower energy less than ~ 375nm
Infrared - higher freque­ncies past ~800

Rydberg Equation

(1.097x107)m-1 = Rydberg's constant

Unit 2 -- Concepts!

LEWIS DOT STRUCTURES
A: Available (valence electrons (number of atoms))
N: Needed (8(nuber of element)+ 2(number of element) )
B: S/2
S: N-A
U:
 
8 - octet if follow octet rule
2 for duet if follow duet rule
 

Calcul­ations

Core Charge
# protons (atomic number) - # inner shell electrons
 
CAN calculate for e- added and use to figure which has a greater electron affinity
Formal Charge
valence electrons - bonds- lone electrons (not lone pairs)
Finding Limiting reagent
take moles of substance A and find how many moles of B gotten
take moles of substance B and find moles of substance A needed
compare moles of each substance
 
moles A/1 * moles B/moles A (in equation)= moles B needed
moles B/1 * moles A/moles B (in equation)= moles A needed
moles A : moles B (calcu­ated)
mol A: mole B in equation
Finding Emperical formula
find moles of each substance
find corres­ponding element's moles based off of
emperical formulas in combustion
* calculate g of C and H and subtract from original compound's mass which gives O's mass
then calculate moles of O
compare ratio of C:H:O
and this gives empirical sub numbers
Finding molecular formula
after calcul­ating Emperical, given molecular weight divide by that of Emperical
multiply ratios by this for sub numbers
Bond Order
½ (# electrons bondin­g-#­ele­ctrons antibo­nding)
Proving Law of Multiple propor­tions
fix one element and
OXIDATION RULES
Molarity
=mol/L

Oxidation Rules

Crysta­lline Structures

Bonds ~ metallic ionic covalent

metallic bonding
between two metals
low EA/ IE/ EN
ionic bonding
forms salts (nonmetal and metal)
metallic solids
shiny
conductors
insoluble in water
"­duc­til­e"
malleable modera­te-high melting points
ionic solid -- salts
hard and brittle
white
soluble in water
not good conductor (unless in solution (disso­lved) or melted)
very high melting point
covalent solids
hard
high melting points
high IE/EN/EA?
molecular solids
soft
low melting pt
 
metallic solids
shiny because...
band theory where the d and s electron energy levels are so close together adn in a lattice there are so many and they are so close they seem to form almost a band that has many energy levels for electrons to jump to.
malleable because in the lattice the electrons are deloca­lized while the nuclei are not. This means that when manipu­lated the electons can freely move making the structure malleable

unit cells

Webassign questions to look at

Webassign
Question
HW 02: WebAssign Questions (Homework)
HELP: 8, 9, 13
Solidify: 10, 11, 14,
HW 02: CDS Questions (Homework)
1
REVIEW: 2

Assessing the Student Response tips

LoMP
make sure one element (mass) is fixed
make sure ra
LoDP

Unit 3 -- Concepts!

 

Unit 4 -- Concepts!

 

Review! dummy

Test
Question
Unit 1 Test
Question 3
 
Question 5
 
Question 7
Unit 2 Test