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CHEM 102: Exam 1
rate of decay=
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kN
k= rate constant
N= number of nuclei (atoms)
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henri becquerel
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discovered radioactivity. put uranium ore in drawer and noticed exposure
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marie curie
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named and characterized radioactivity - discovery of radium and polonium
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ernest rutherford
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golf oil experiment.
planetary model of atom. this didn't work because electrons would spiral into nucleus
discovered nucleus
-performed the first artificial nuclear reaction
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Z
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number of protons
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A
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mass #
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Alpha emission
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-most commonly with anything bigger than bismuth
-followed by gamma radiation
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gamma emission
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-often results from "relaxation" of nucleus following loss of particles
-no change in Z or A
-travel far
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beta emission
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n --> B + P
-decreaes neutron/proton ratio
-produces protons
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nuclear transmutation
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change in one nuclear particle to another in the decay process
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positron emission
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-increases neutron/proton ratio
p --> n + positron
produces neutron
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electron capture
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P + e --> n
-increaeses neutron/proton ratio
-produces neutron
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spontaneous fission
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some bigger nuclei spontaneously break into smaller nuclei and neutrons
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what is n/p ratio above bismuth
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1.5/1
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Magic numbers
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2,8,20,28,50,82,126
even Z have more stable than odd Z
even Z have more stable isotopes if even n
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stable isotopes
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even/even
even p/ odd n
odd p/ even n
odd/odd
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radionuclides
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all the isotopes of all the elements
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half life=
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.693/k or k= .693/half life
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carbon-14 dating
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- half life is 5715 years
-based on the assumption that things decay at the same rate as they did 50,000 years ago
-works up to 10 half lives
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binding energy
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-uses the mass defect
- e=mc2
-accoring to binding energies, all elements in the universe are unstable relative to iron
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Fermi national lab in illinois
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high energy methods for causing particle collisions
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brookhaven national lab
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new york
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biggest collider in the world
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large hadron collider, switzerland.
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neutron activation
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takes nonradioactive substance, adds neutrons, makes the substance radioactive. you can then figure out what elements are in there based on radioactive energies.
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fission reactions
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-Hahn, strassman, meitner, bohr all discovered that u-235 could be stimulated to undergo fission by neutron bombardment
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enrico fermi
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carried out the chain first sustained reaction on the squash courts in chicago
-manhattan project
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inititation
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the start of the fission process (we use neutrons for that)
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propagation
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the actual chain reaction
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termination
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remove/absorb the neutrons to stop the reaction
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"sustained" chain reaction
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each fission process causes at least one additional fission process to keep reaction going
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critical mass
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the proper mass and density necessary for sustaind chain reaction
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"multiplying" chain reaction
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each fission process produces more than one additional fission
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"supercritical mass"
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greater than critical mass
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nuclear enrichment
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increasing % of u-235 inside u-238
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HEU
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highly enriched uranium
-95.99
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methods of enrichment
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gaseous diffusion
ultracentrifugation
laser enrichment
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gaseous diffusion
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-oldest method
-used this in the manhattan project
-you make gas. lighter gas (u-235) will diffuse faster. thus it will separate
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ultracentrifugation
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-newer way
-centrifuge spins and separates based on mass/density
-spin in high rpm and heavier isotopes separate from lighter isotopes
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laser enrichment
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NC is capitol of the world for this
-lasers excite and ionize one isotope preferential to the other. if you can do this, you can extract something ionized (based one charge) to an electric plate. this separates the isotopes.
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nuclear enrichment tools
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they are the "smoking gun" for new nuclear programs
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fusion reactions
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-energy is released when lighter nuclei are combined to form heavier ones. (stellar energy source)
-sun
-occurs at tremendous heat and pressure
-no critical mass
-energy depends on mass defect
-is a very appealing source of energy b/c it is very abundant (needs protons aka hydrogen)
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experimental history of fusion
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-not much has been done.
-"cold fusion hoax" scientists at bringham young.
-movie "the saint"
-power generation
-weapons
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tokamak fusion reactor
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"magnetic bottle"
-magnetic chamber + they put plasma in it
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food irradiation
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-with gamma source with Co-60 or Cs-137
-they irradiate food to kill biological organisms
-still protested (could be carcinogenic)
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cancer treatment
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-greatest application for nuclear chemistry
-use gamma source to kill fast growing cells.
-target cell's reproductive area
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radiotracers - iodine, iron, phosphorous, technetium, thallium, sodium
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iodine- thyroid
iron- red blood cells
phosophorous - eyes,liver,tumors
technetium - skin cancer, pools in lymph system, heart bones, liver, lungs
thallium- heart, arteries
sodium- circulatory system
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isotope dillution
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finding volumes of unknown cavities in the ground using radioactive isotopes
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two main types of reactors
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pressurized water reactor (shear on harris)
boiled water reactor
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containment vessel
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surrounds the core of the reactor where reaction is; contains fuel and control rods
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secondary containment bldg
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heavily reinforced concrete building. around a containment vessel
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coolant
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typical one is water, and heavy water. or liquid metals (sodium)
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moderator
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slows down neutrons which makes reaction happen. it makes it easier for neutrons to hit their target. Slowing down neutrons lowers energy
-usually water, sometimes graphite
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fuel rods
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encriched uranium oxide pellets in a non-neutron absorbing case. this case is usually zirconium
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control rods
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opposite of fuel rods. they absorb neutrons. this is where you slow down neutrons.
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little boy
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-tickling the dragon
-used uranium-235
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implosion type
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-used plutonium-239 to supercritical mass/density
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fat man
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-nagasaki
-implosion type
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fusion weapons
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-thermonuclear
-no critical mass needed
-intitiated by fission weapon
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Becquerel
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1 dps.
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Curie
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-nonmetric
-3.7e10 Bq
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Roentgen
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generic measure of radiation exposure
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RAD
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stands for radiation absorbed dose measured in J/kg
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REM
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Roentgen equivalent to men depends on type of radiation and tissue involved
-start to see slight effects after 25 rem
-500 rem death of half the population in 30 days
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Radon
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-not very dangerous
-builds up on basements because of soil
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NVD
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nausea, vomitting, diarhea
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reactions for airbags
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-involves sodium azide--> sodium, nitrogen gas
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elements that are gases at room temperature
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02, n2, h2, he, cl2, f2, ne, ar, rn, kr, xe
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dangers of hcn
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bitter almonds
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dangers of h2s
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rotten eggs, toxic
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dangers of Ch4 (methane)
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flammable
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dangers of C2h4 (ethylene)
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ripens fruit
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dangers of n2o
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laughing gas
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dangers of no2
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red-brown
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dangers of so2, nh3
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odorous
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Pressure =
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Force/ Area
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Force =
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mass(kg) x acceleration
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1 atm
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760 torr
101.325 kPa
14.7 psi
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newton=
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kg- m/s2
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1 pascal=
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N/m2
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Boyle's law
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V and P are inversely related
-u-tube illustrates it graphically
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charles law
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V and T are proportional
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absolute zero
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-273.15 K and 0 C
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Avogadro's law
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V and n are proportional
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Gay-Lussac
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P and T are proportional
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density =
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P= d (RT/M)
density is in g/L
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gas mixtures and partial pressures
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- in a mixture of gases, each component gas contributes to the tool pressure according to its number of moles. specifically, according to the mole fraction
-mole fraction x total pressure = partial pressure
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toal pressure=
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pressure of the gas collected + pressure of what water vapor.
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kinetic molecular theory
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- gases are compressible, take shape of container
- gases can be liquefied: implies intermolecular forces are possible
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tenets of kinetic molecular theory
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1. gases consist of large number of atoms/molecules in continuous, random motion
2. gas molecules are vey small relative to the distances between them (volumes are negligible )
3. negligible attractive/repulsive forces between atoms
4. only elastic collisions occur b/w molecules. Average kinetic energy remains constant as long as temp. is constant
5. average kinetic energy is proportional to temperature. at same temperature, all gases have the same kinetic energy
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average kinetic energy-
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1/2 mu2
m- mass in kg
u- root means square speed in m/s
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root mean square speed is generally faster than
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the most probable speed.
average = .921 x rms speed
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maxwell's equation- DONT FORGET UNIT
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square root (3RT/M)
M is in kg/mol
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diffusion
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mixing of gases due to molecular motion
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effusion
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the movement of a gas through a little hole by molecular motion
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graham's law
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rms speed is inversely related with square root of molar mass. tHIS IS RATE
- WHEN TALKING ABOUT TIME they are directly proportional
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why does ideal gas law work
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-occupy little space
-negligible interactions
-volumes are negligible
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when does ideal gas law fail?
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at high pressures - it pushed molecules together and then interactions and volumes are no longer negligible
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Van der waals equation
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-used in gas studies at non ideal conditions
- look in notes page 68 for ths.
- the b corrects for molecular volumes at high pressures
- the a corrects for molecular attractions
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All IM forces are less than covalent and ionic
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ionic is strongest
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densities of different phases
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densities of gases are very small. densities of liquids and solids are pretty similar
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elements that are liquid at room temperature
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mercury and bromine
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Ion-Dipole
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-strongest
-you must have an ion and a dipole
-need an ion and it must be polar. covalently bonded that has uneven distribution of electrons
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Dipole Dipole
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-second strongest
-need 2 dipoles
-between 2 polar molecules
-Water is an example - hydrogen bonding
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Dipole- induced dipole interaction
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-third strongest
-need dipole and induced dipole (any compound)
-used mostly in discussions of non-polar compounds because they can be induced dipole
-induced is weaker than regular dipole
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induced dipole - induced dipole
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-weakest
-all molecules are this
-called dispersion
-give instantaneous dipole
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force ion-dipole
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inversely proportional to distance
force = (magnitude e+)(magnitude e-) / distance2
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strength of ion-dipole depends on
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- force inversely proportional to distance
- charge of ion
- magnitude of dipole (how polar)
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can you have polar bonds within the molecule , yet the whole molecule is non polar?
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yes. ch4.
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heat of vaporization is...
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endothermic. positive heat in order to break bonds.
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Strong IM forces mean..
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higher boiling point and MP. it is harder to break them
-less "volatile" means higher BP
-stronger IM means less volatile
-weaker IM means mores volatile - they are much more dangerous- easy to boil
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hydrogen bonding
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- need F, N, or O
- they are particularly strong dipole-dipole
- proteins, DNA, enzymes
- high surface tension, liquid at room T
- energy is 4-25 kj/mol
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london dispersion forces
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explain why i2 is solid at room temp.
- increase with increasing MW
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factors affecting dispersion forces
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-MW
-shape - molecule must be close to one another to "feed" strong induced forces
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viscosity
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-resistance to flow
-relates to the strength of the IM forces
-decreases with temperature that is increasing
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surface tension
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-energy required to increase the surface area of a liquid by a unit amount (energy required to break a droplet into a film)
- think how car wax and water droplets. you are adding surface that is non polar that means the metal is not tugging on the water
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cohesive
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forces b/w liquid molecules are stronger. hg is nonpolar
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adhesive
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forces between liquid and surface of container
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capillary action
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th movement of a liquid up a narrow tube by adhesive forces
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heat of vaporization
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heat required to vaporize a liquid at constant pressure
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heat of fusion
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the energy required to melt
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for phase changes
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number of moles x heat of vaporization or fusion
-horizontal lines is for mol x heat
-vertical lines are q=m(specific heat) (change temperature)
-horizontal lines - no longer changing temperature, only breaking IM forces. Energy is going into breaking the IM forces, not actually changing the temperature
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vapor pressure
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pressure established over a liquid by molecules/atoms that escape from the liquid phase into the vapor phase (equilibrium)
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higher VP=
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lower BP
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dew point
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where air is 100% saturated with water vapor equal to or less than current temperature
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clausius clapeyron equation
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lnp= -(Hvap/RT) + C
study 444
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critical temperature
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maximum temperature at which a substance can be liquefied
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critical pressure
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pressure necessary to liquefy a substance at critical temperature
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liquid crystal
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a chemical compound that exhibits an intermediate phase between solid and liquid. tend to be long molecules and one end is polar, the other is non polar
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nematic liquid crystal
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long axes of molecules aligned, but ends are not aligned
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smectic a liquid crystal
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molecules aligned in layers, long axes perpendicular to layer planes
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smectic c
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molecules aligned in layers, long axes of molecules inclined
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cholesteryl liquid crystal
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layers and go in directions, rotating
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