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CHEM 0110: Exam 2
Density Formula
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d= (p*MM)/RT
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Gas Laws
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p1V1=p2V2
p1/T1=p2/T2 |
total pressure
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sum of all partial pressures
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Calculating ΔH
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final energy-initial
exo: ΔH of the system is negative
endo: ΔH of the system is positive |
Breaking Bonds is....
Forming Bonds is... |
breaking: endothermic
forming: exothermic |
Exothermic Reactions
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combination (can be endo), single displacement, combustion
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Endothermic Reactions
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decomposition (can be exo), vaporization, melting
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What is ΔH?
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heat transferred when the reaction is carried out under conditions of constant pressure
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specific heat of water
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4.18 J/gCelsius
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q always refers to what?
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the surroundings
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relationship between wavelength and frequency if c is constant
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inversely proportional
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wavelength for:
red light
blue light |
red: 700nm
blue: 400 nm |
photon |
smallest unit of light energy
energy of photon=hv |
Visible Light
(Infrared to UV) |
wavelength decreases
frequency increases
Ephoton increases |
When light is absorbed by matter...
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individual atoms or molecules absorb 1 photon at a time
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3 Labels to characterize an orbital
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n, l, ml
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n |
quantum number
determines energy and size of orbital |
l |
quantum number
defines overall shape of electron cloud |
ml |
quantum number
defines orientation of the orbital |
Differences between H and other atom
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energies of orbitals decrease as protons added
energies depend on n and l |
Magnetic properties
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you have to have one or more unpaired electron
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paramagnetic
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with one or more unpaired electron and it's magnetic
|
diamagnetic |
with no unpaired electron
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Exceptions to electron configuration
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Cu, Ag, Au, Cr
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Ionization Energy
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-energy needed to remove highest energy electron from the atom
-ranges from 400 - 2400 kJ/mol
-always an endothermic process
-increases as you move up and to the right of periodic table |
Electron Affinity
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-energy needed to add an electron to an atom
-often exothermic
-halogens have most exothermic EA
-noble gases have endothermic values
-small compared to IE
-ranges from 350 to -50 kJ/mol
-increases as you move up and to the right to the periodic table |
Atomic Size
|
related to size of the largest valence orbital of the atom
large orbital=large atomic size=small IE
small orbital=small atomic size=large IE
increases as you move down and to the left of the periodic table |
Electronegativity |
ability of an atom to attract an electron to it from another atom to which it is bonded
-increases as you move up and to the right to periodic table |
Large and Small EN
|
Large: high electron attracting power
-active non-metals
Small: low electron attracting power
-active metals |
EN: 0.7-1.5
2.5-4.0
2.0
2.1 |
0.7-1.5: fairly active metal
2.5-4.0: fairly active non-metal
2.0: metalloids
2.1: hydrogen |
Exceeds Octet rule
|
3rd and 4th period
|
-ane
-ene
-yne |
-ane: single bond
-ene: double bond
-yne: triple bond |
Bond length and dissociation energy
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bond length decreases from single to triple
dissociation energy increases from single to triple |
Exceptions to Octet Rule
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-species with odd number of electrons
-elements beyond 2nd period
-electron deficient species |
1 atm=
|
76cmHg = 760 mmHg
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Atmospheric pressure and altitude
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pressure decreases when altitude increases
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at constant n and T: p and V are...
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inversely proportional
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at constant n and V: p and T are...
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directly proportional
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molecular speed increases with... and decreases with...
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temperature and increasing mass
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Hess's Law
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No matter how many steps you go through to get a reaction, the enthalpy change is always the same
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Boyle's Law
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pressure and volume are inversely related when at a given temperature
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Kinetic Theory of Ideal Gas
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1. Molecules spread out in space so separation > molecular size
2. Molecules moving rapidly
3. Pressure due to molecules bouncing off walls of container
4. Gas molecules collide and are elastic |
mole fraction
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Xa= (Na/Ntotal)=(Pa/Ptotal)
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Hund's Rule
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In a set of orbitals with the same energy, electrons tend to occupy different orbitals with the same spin.
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paulie exclusion principle
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states that a max of 2 electrons can occupy a sungle orbital , but only if the electrons have opposite spins
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Gas Laws in General:
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(P1*V1)/(n1/T1)=(P2*V2)/(n2/T2)
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Rules for determining delta H from bond energies
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bonds broken-bonds formed
|
y2 |
y2 is the probability of finding the electron in a small volume at a distance r from the nucleus
-part of Schrodinger equation |
Diamagnetic |
all spins are paired, not attracted to a magnetic field
|
paramagnetic |
unpaired spins, attracted to a magnetic field
|