ch 20 & 21 test Flashcards
electrochemistry
the study of the relationships between electricity and chemical reactions. It includes the study of both spontaneous and non-spontaneous processes
oxidized
oxidation number increases for an element. Losses electrons.
reduced
oxidation number decrease for an element. Gains electrons.
voltaic cell
a spontaneous redox reaction, electrons are transferred and energy is released
anode
(-) where oxidation occures. e^- on right side.
cathode
(+) where reduction occures. e^- on left side.
metal deposition
as the electrons reach the cathode, cations in solution are attached to the now negative cathode.
Ecell°=
E°red(cathode)-E°red(anode)
the more positive the value of E°red
the greater the tendency for reduction
the strongest oxidizing agents
have the most positive reduction potential
the strongest reducer
have the most negative reduction potentials
a redox rxn is sponatenous if
- E°cell is +
- delta G is -
- K is greater than 1
batteries
portable self-contained electrochemical power source that consists of one of more volatic cells.
alkaline battery
the most common primary battery
lead-acid battery
reactants and products are solids. made with lead and sulfuric acid (hazards).
Ni-Cd and Ni-metal hybride batteries
- lightweight, rechargeable
- hydrides replace Cd since Cd is toxic
Lithium-ion battery
rechargeable light; produce more voltage than Ni-based batteries.
fuel cells
when a fuel is burned, the energy created can be converted to electrical energy.
hydrogen fuel cells
-in this cell, hydrogen and oxygen form water.
-the cells are twice as efficient as combustion.
-the cells use hydrogen gas as the fuel and oxygen from the air.
corrosion
is oxidation and often leads to structural and mechanical failure. The common name is rusting.
cathodic protection
a metal is sacrificed based on the standard reduction potentials.
sacrificial anode
used to prevent corrosion of iron underground pipes. Is attached to the pipe. The anode is oxidized before the pipe.
electrolysis
non-spontaneous chemical reactions can now occur if outside electricity is used to drive the reaction.
steps to balance acidic equations
- split into two equations
- balance main equation elements
- add H2O and H+ to balance the O and H
- add e^- to balance charges
- distribute opposite charge to respected equations.
- combine equations.
steps to balance basic equations
1.split equations
2. redox numbers filled
3. balance main equation elements
4. add H2O and H+ to balance O and H
5. add OH^- to balance the H+ to make H2O
6. find charges and balance e^-
7. distribute to make e^- equal for both equations
8. if you have H2O on both sides of equation simplify
9. combine equations
mass number
number of protons and neutrons together
atomic number
number of protons
isotopes
atoms of the same element have different mss due to different numbers of neutrons in those atoms
alpha decay
is the loss an alpha particle 4/2He
beta decay
the loss of a beta particle 0/-1e
gamma radiation
is the loss of a gamma ray which is high energy radiation that almost always accompanies the loss of a nuclear particle 0/0Gamma
positron emission
some nuclei decay by emitting a positron, a particle that has the same mass as but an opposite charge to that of an electron. 0/1e
electron capture
an electron from the surrounding electron cloud is absorbed into the nucleus. 0/-1e
belt of stability
shows which nuclides would be stable
particle accelerators
(atom smashers) are enormous using strong magnetic and electric fields to make the particles move so fast
linear accelerator
has tubes of variable lengths and charges to make the particle move faster
cyclotron
uses D-shaped magnets to keep particle moving in a spiral
synchrotron
accelerates particles in a path, which is circular.
carbon dating
the half life of C-14 is 5730 years.
Becquerel (Bq)
one nuclear disintegration per second
Curie (Ci)
defined as 3.7X10^10 disintegrations per second. This is the rate of decay of 1g of radium.
Film Badges
radioactivity was first discovered by Henri Becquerel because it fogged up a photographic plate
Geiger counter
measure the amount of activity present in a radioactive sample.
phosphors
some substances absorb radioactivity and emit light.
radio tracers
are radioisotopes used to study a chemical reaction.
medical application of radiotracers
are administered to a patient and followed certain elements collect more in certain tissues, so an organ or tissue type can be studied based on where the radioactivity collects.
Positron emission tomography (PET)
a compound labeled with a position emitter is injected into a patient. blood flow, oxygen and glucose metabolism, and other biological functions can be studied.
mass defect
mass differenece
nuclear binding energy
energy needed to separate a nucleus into its nucleons
fission
heavy nuclei gain stability and give off energy when they split into two smaller nuclei
fusion
lighter nuclei emit great amounts of energy by being combined in fusion
thermonuclear reactions
reactions that occur on the sun
outside the body
gamma rays are most dangerous
inside the body
alpha radiation can cause most harm
Gray
Gy; absorption of 1 J of energy per kg of tissue
rad
for radiation absorbed dose; absorption of 0.01 j of energy per kg of tissue (100rad=1Gy)
Relative biological effectiveness RBE
is used to show how much biological effect there is
rem
the effective dose # of rem=(#of rad)(RBE)
