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Test 2
Ch 5-8
50
Chemistry
Undergraduate 2
03/02/2009

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Term
Thermodynamics
Definition
the science of heat and work
Term
Energy
Definition
capacity to do work or transfer heat
Term
Kinetic energy
Definition
energy of motion:
thermal-motion of particulate level
mechanical-motion of macroscopic objects
electrical-motion of electrons through conductor (redox, batteries)
Term
potential energy
Definition
results from position:
gravitational-energy possessed at certain height
chemical-energy in fuels
electrostatic-energy associated w/separation of two electrical charges (atoms attract to form bonds, lowers potential)
Term
temperature
Definition
measure of its ability to transfer energy as heat (determines direction of thermal energy transfer.. higher temp = higher thermal energy)
Term
system/surroundings
Definition
system is object being studied, surroundings are everything outside the system that can exchange energy/matter w/the system
Term
exothermic process
Definition
energy transferred as heat from a system to its surroundings (energy of system decreases, energy of surroundings increases)
Term
endothermic process
Definition
energy is transferred as heat from the surroundings to the system (energy of system increases, energy of surroundings decreases)
Term
calorie
Definition
energy transferred as heat that is required to raise the temp of 1 g pure water 10 degrees (1 cal = 4.184 J)
Term
energy depends on:
Definition
quantity of material, magnitude of temp change, identity of material gaining or losing energy
Term
specific heat capacity
Definition
energy transferred as heat that's required to raise the temp of 1 g of a substance by 1 K q=cmT (intensive property)
Term
heat of fusion
Definition
energy transferred as heat that's required to convert a substance from a solid at its melting point to a liquid
Term
heat of vaporization
Definition
energy transferred as heat to convert a liquid at its boiling point to a vapor. Added energy is used to overcome forces holding the molecules together, not to increase the temp, which stays the same as the state changes)
Term
energy and work
Definition
if a system does work on its surroundings it expends energy (system's energy decreases as surroundings' energy increases). if work is done by the surroundings, the system gains energy
Term
first law of thermodynamics
Definition
U=q + W all energy transfers b/w a system and the surroundings occur by processes of heat and work
Term
internal energy, U
Definition
KE + PE
energy transferred as heat:
to the system(endothermic) -q(+)-U increases
from the system(exothermic)-q(-)-U decreases
work done on system-W(+)- U increases
work done by system-W(-)-U decreases
Term
enthalpy, H
Definition
H=U+PV heat energy transferred at constant pressure
-H : energy as heat from system to surroundings
+H : energy as heat from surroundings to system
Term
standard reaction enthalpy
Definition
enthalpy change of a reaction that occurs w/all reactants and products in their standard states
- for exothermic, + for endothermic
Term
calorimetry
Definition
measures energy evolved/required as heat in a chemical/physical process. Change happens as chemical reaction occurs; energy is gained/lost as heat by the solution
Term
Hess's law
Definition
if a reaction is the sum of 2+ other reactions, standard reaction enthalpy for the overall process is the sum of the standard reaction enthalpies of those reactions
Term
standard molar enthalpies of formation
Definition
enthalpy change for the formation of 1 mol of a compound directly from its component elements in their standard states.
is zero for element in standard state.
most values are - (exothermic)
Term
product favored
Definition
reactions where reactants are largely converted to products at equilibrium (- values of standard reaction enthalpy)
Term
reactant favored
Definition
reactions where only a small amount of products are present at equilibrium (+ values of standard reaction enthalpy)
Term
electromagnetic radiation
Definition
radiation that consists of wave-like electric and magnetic fields
Term
Plank's energy eqn
Definition
E=nhv where h is plank's constant (6.63e-34 J s), v is frequency. energy is quantized (only certain energies allowed)
Term
photoelectric effect
Definition
electrons are ejected when light strikes the surface of a metal if the frequency of light is high enough (shows that light can behave as particles)
Term
photons
Definition
energy of each photon is proportional to the frequency of radiation (photons striking atoms on a metal surface will eject electrons iff. photons have enough energy)
Term
potential energy of electron in nth energy level
Definition
E=-Rhc/n^2 R is Rydberg constant (R=1.0974e7), h is plank's constant
to move an electron from ground state to higher state energy must be absorbed. if electron falls from higher n to lower n energy is released
Term
lyman series
Definition
electron falls from n>1 to n=1
Term
balmer series
Definition
electron falls from n>2 to n=2
Term
Heisenberg's uncertainty principle
Definition
any attempt to accurately determine either the location or energy of an electron will leave the other uncertain
Term
quantum mechanics
Definition
uses mathematical eqns of wave motion to generate a series of eqns called wave eqns:
1. an electron in the atom is described as a standing wave 2. by defining the electron as s standing wave, quantization is introduced into the description of electronic structure 3. each wave fxn is associated w/an allowed energy value 4. the value of the wave fxn at a given point in space is the amplitude of the wave 5. at any point in space, the square of the value of the wave fxn defines the probability of finding the electron (electron density) 6. Schrodinger's theory defines energy of electron, uncertainty principle says there is uncertainty in is location, so we describe the probability of the electron being w/in a certain region in space when in a given energy state
Term
principle quantum number, n
Definition
primary factor in determining the energy and size of an orbital (greater n = greater size of orbital). same n value: electrons in same electron shell
Term
azimuthal quantum number, l
Definition
defines characteristic shape of an orbital:
l=0, s subshell
l=1, p subshell
l=2, d subshell
l=3, f subshell
Term
magnetic quantum number, m(l)
Definition
related to orientation in space of orbitals w/in a subshell (ranges from -l to l where 2L +1 is the # orbitals in subshell m(l)
Term
s orbitals
Definition
n=1, l=0, most likely found near nucleus, spherical, has boundary surface, max electrons: 2
Term
p orbitals
Definition
l=1, dumbbell shape, three p orbitals in a subshell, max electrons: 6
Term
d orbitals
Definition
l=2, 5 d orbitals, "donut", max electrons: 10
Term
f orbitals
Definition
l=3, electron density in 8 regions of space, max electrons: 14
Term
electron spin quantum number, m(s)
Definition
if atoms w/a single unpaired electron are placed in a magnetic field, there are 2 orientations for the atoms: spin aligned with or opposed to the field
m(s) is quantized: =+/- 1/2
Term
paramagnetism
Definition
attraction to a magnetic field of substances in which the constituent ions or atoms contain unpaired electrons
Term
pauli's exclusion principle
Definition
no two electrons in an atom can have the same set of four quantum numbers(n,l,m(l), m(s))
Term
aufbau principle
Definition
procedure that assigns electrons to orbitals. assigned to n shells and l subshells inorder of increasingly higher energy
Term
rules to predict arrangements of electrons
Definition
1. electrons are assigned to subshells in order of increasing "n & l" values
2. for two subshells w/the same value of n & l, electrons are first assigned to the subshell of lower n
Term
effective nuclear charge, Z*
Definition
net charge experienced by a particular electron in a multielectron atom resulting from the nucleus and other electrons
going across a period, Z* increases (increases attraction b/w nucleus and valence electrons)
s>p>d>f
Term
hund's rule
Definition
the most stable arrangement of electrons is that w/the max # of unpaired electrons, all w/the same spin direction
Term
atomic radii
Definition
for main group elements: radii increase going down a group and decrease going across a period (due to Z*)
Term
ionization energy, IE
Definition
energy required to remove an electron from an atom in gas phase. to separate an electron from an atom energy must be supplied to overcome attractive nuclear charge. each subsequent electron requires more energy for removal
Term
electron affinity, EA
Definition
energy change for a process in which an electron is acquired by the atom in the gas phase. the greater the EA the lower the energy of the ion (high IE means more -EA)
Term
isoelectronic ions
Definition
same # electrons but different # protons. as # protons increases in a series of isoelectronic ions, the balance b/w electron-proton attraction and electron-electron repulsion shifts in favor of attraction and the radius decreases
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