Test Three Flashcard

thermodynamics
study of energy and its transformations
thermochemistry
branch of thermodynamics that deals with heat in chemical and physical changes
system
part of the universe that is being focused on
surroundings
everything (in reason) that is not the system
internal energy E
sum of all kinetic and potential energy of each particle in a system
DE =
Efinal – Einitial
Eproducts – Ereactants
q + w
a change in energy of the system must be accompanied by
an equal and opposite change in energy of the surroundings
releasing energy in a transfer to the surroundings
Efinal < Einitial so DE<0
absorbing energy in a transfer from the surroundings
Efinal > Einitial so DE>0
q symbolizes
heat
heat –
energy transferred as a result of the difference in temperature between the system and the surroundings
w represents
work
work –
energy transferred when an object is moved by a force
energy transferred into the system is
positive because the system ends up with more energy
DE is positive
energy transferred out of the system is
negative because the system ends up with less energy
DE is negative
the law of energy conservation
the 1st law of thermodynamics
the total energy of the universe is constant
joule (J)
SI unit for energy
1 J =
1 kg*m^2/s^2
calorie (cal)
quantity of energy needed to raise the temperature of 1 gram of water by 1 *C
1 cal = _____ J
4.184 J
1 J = ___ cal
0.2390 cal
the internal energy of a system is called a
state function
a state function is dependent on
the current state of the system, not on the path the system takes to reach that state
DE depends on
the difference between the final and initial states, not on how the change takes place
pressure-volume work (PV work)
mechanical work done when the volume of the system changes in the presence of eternal pressure
w =
-P DV
H stands for
enthalpy
enthalpy-
internal energy plus the product of the pressure and volume
H =
E + PV
DH =
DE + P DV
the change in enthalpy equals
the heat absorbed or released at constant pressure
exothermic process
releases heat and results in the decrease in the enthalpy of the system
endothermic process
absorbs heat and results in an increase in the enthalpy of the system
q =
c * mass * DT
heat capacity –
quantity of heat required to change its temperature by 1 K
heat capacity =
q / DT
specific heat capacity –
quantity of heat required to change its temperature of 1 gram of the object by 1 K
c represents
specific heat capacity
c =
q / (mass * DT)
molar heat capacity –
quantity of heat required to change its temperature of 1 mole of the substance by 1 K
C represents
molar heat capacity
coffee cup calorimeter
device that measures the heat transferred at constant pressure
bomb calorimeter
device measures the heat released at constant volume
thermochemical equation
balanced equation that includes the enthalpy change of the reaction
Hess’ Law
the enthalpy change of an overall process is the sum of the enthalpy changes of its individual steps
DHoverall =
DH1 + DH2 + DH3…
standard state for a gas
at 1 atm and ideal behavior
standard state for a for a substance in aqueous solution
1 M concentration
standard state for a for a pure substance (element or compound)
the most stable form of the substance at 1 atm and 25*C (298K)
in a formation equation
1 mol of a compound forms from its elements
standard enthalpy of formation
enthalpy change for the formation equation when all the substances are in their standard states
the standard enthalpy of reaction is
the sum of the standard enthalpy of formation of the products minus the sum of the standard enthalpy of formation of the reactants
examples of fossil fuels
petroleum, coal and natural gas
Kinetic Energy
The energy associated with motion
Thermal Energy
Motion of atoms, molecules or ions at the submicroscopic level
Mechanical Energy
Motion of a macroscopic objects like a moving basketball or airplane
Electrical Energy
Movement of electrons through a conductor
Acoustic Energy
The compression and expansion of molecules in the transmission of sound.
Potential Energy
The energy associated with an objects position
types of kinetic energy
Acoustic Energy
Electrical Energy
Mechanical Energy
Thermal Energy
Gravitational Energy
Energy possessed by a ball held above the floor or by water at the top of a water fall
Chemical Energy
Energy stored in fuels or in chemical bonds
Electrostatic Energy
The energy associated with the separation of two electrical charges.
Types of Potential energy
Gravitational Energy
Chemical Energy
Electrostatic Energy
Law of Conservation of Energy
Energy can neither be created nor destroyed
w stands for
Energy transferred as work to or from the system
Internal Energy
The formal name for the quantity E.
Internal energy in a chemical system is the sum of PE and KE of the atoms, molecules or ions
enthalpy is
equal to the amount of energy transferred as heat at a constant pressure.
If ?H is negative,
energy is transferred as heat from the system to the surroundings. Exothermic.
If ?H is positive,
energy is transferred as heat from the surroundings to the system. Endothermic.
The temperature of an object is a measure of
its ability to transfer energy as heat.
The higher the temperature,
the greater the thermal energy of the materials atoms, ions or molecules
Thermal Equilibrium
When two objects which were once at different temperatures, reach the same temperature
Energy transfer as heat will occur spontanesosly from _____ to ______
the higher temperature material to the lower temperature material
Calorimetry
The method by which the energy evolved or required as heat in a chemical of physical process is measured.
Change of State
conversion of a substance from one physical state to another, i.e. from a liquid to a solid or from a liquid to a gas
Heat of Fusion
The energy transferred as heat that is required to convert a substance from a solid to a liquid
Heat of Vaporization
The energy transferred as heat that is required to convert a substance from a liquid to a gas
The superscript o indicates that
the reaction has been run at standard conditions.
Enthalpy changes are specific to
the reaction being carried out. State of the product produced, is important as are the amounts of products and reactants.
The enthalpy change depends on the
number of moles of reaction. That is how many times the as written reaction is carried out.
Electromagnetic Radiation
Characterized by wavelength and frequency and includes light, microwaves, television and radio signals x-rays, and other forms of radiation
wavelength
ambda, ?, the distance between successive crest or high points of a wave. The distance is usually measured in m or nm
frequency
nu, ?, refers to the number of waves that pass a given point in some unit of time, usually per second. The unit of frequency, written as s-1 or 1/s is called hertz.
Clight =
Clight = 2.99792458 x 108m/s
Magnetic vector moves _______ to that of the electric vector
perpendicular
Nodes:
where the wave changes from positive to negative
Plank Assumed
that the EMR emitted was caused by vibrating atoms called oscilators. And if each oscilator had a frequency, and the emitted radiation had a certain energy, the following eqn could be written.
Plank’s Constant:
h = 6.6260693 x 10 -34 J*s
E=
h * wavelength
Photoelectric Effect
electrons are ejected when light strikes the surface of a metal.
The energy of each photon is proportional to
the frequency of the radiation as defined by Planck’s eqn.
Einstein
Photoelectric Effect
Line Emission Spectrum
The spectrum obtained from passing a beam of light from the excited sample through a prism.
Balmer Equation
1/ lambda = R (1/22 – 1/n22), where n is an integer and > 2
Rydberg Constant
R = 1.0974 x 107 m-1
Balmer series.
The 4 visible lines in the spectrum of hydrogen
Bohr derived an equation for
the energy possessed by the single electron in the nth orbit of the H atom
Bohr Equation
En = – Rhc / n2
n defines the
energies of the allowed orbits in the H atom
deBroglie
Proposed that matter which was normally considered a particle, could also exhibit wave properties. Previously for light in the photoelectric effect.
Bohr Model:
That both the energy and the location for the electron in the hydrogen atom can be described accurately
Heisenberg:
Determined that for an object such as an electron in an atom, it is impossible to determine accurately both its position and its energy.
Heisenberg Uncertainty Principle:
any attempt to determine accurately either the location or the energy will leave the other uncertain.
Schrodinger
Developed quantum mechanics or wave mechanics. Uses mathematical eqns of wave motion to generate wave functions which are used to describe a electrons in the atom.
the principle quantum number
n
The value of n, is
the primary factor in determining the energy and size of an orbital.
For any given atom, the greater the value of n,
the greater the size of the orbital.
Orbitals are grouped into _____ .
subshells
each subshell is characterized by a different value of ____
I
I defines the characteristic
shapes of the orbitals.
mf is related to the
orientation in space of the orbital within a subshell.
Paramagnetic
Elements or compounds that have unpaired spins and are attracted to magnets.
Diamagnetic
Substances in which all the electrons are paired (with 2 electrons in each pair, having opposite spins) experience a slight repulsion when subjected to a magnet
electron spin quantum number
ms
frequency
the number of cycles a wave undergoes per second
electromagnetic radiation consists of
energy propagated by electric and magnetic fields that increase and decrease in intensity as they move through space
visible light, x rays and microwaves are examples of
electromagnetic radiation
wavelength
the distance between any point on a wave and the corresponding point on the next crest of the wave
the distance the wave travels in one cycle
speed of light (c) =
wavelength * frequency
amplitude
the height of the crest of wave or the depth of the trough
the amplitude of a wave is related to the
intensity of the radiation
types of waves by increasing wavelegth
gamma
x-ray
ultraviolet
visible
infrared
microwave
radio
types of waves by increasing frequency
radio
microwave
infrared
visible
ultraviolet
x-ray
gamma
visible light goes from
400 nm (violet) to 750nm (red)
refraction
when a light wave passes through on medium and into another and the speed of the wave changes, making the wave bend in shape
dispersion
white light separates into its component colors when it passes through a prism
diffraction
when a wave strikes against an object and it bends around it
blackbody radiation
when a solid object is heated to about 1000 K and it begins to emit visible light
the quantum theory was created by
Planck
the photon theory was created by
Einstein
wavelength and frequency have a _____ relationship
reciprocal
line spectrum
a series of fine lines at specific frequencies separated by black spaces
Rydberg equation predicts
the position and wavelength of any line in a given series
Rydberg equation
(1 / wavelength) = R ((1 / n1^2) – (1 / n2^2))
the Hydrogen model atom was created by
Bohr
Postulates of Bohr’s Hydrogen Atom Model
the H atom has only certain energy levels
the atom does not radiate energy while in one of its stationary states
the atoms changes to another stationary state only when absorbing or emitting a photon
ground state
when the electron is in the first orbit, is closest to the nucleus and the H atom is in the lowest (first) energy level
excited state
if the electron is in any orbit other than the first orbit
an atomic spectrum (is/ is not) continuous because
is not; the atom’s energy is not continuous, but rather has only certain states
an atom changes energy by
absorbing or emitting a photon of specific energy
Bohr’s Equation
DE = Efinal – Einitial = -2.18×10^-18 J ((1/ nfinal^2) – (1/ninitial^2))
emission spectrum is produced when
atoms in an excited state emit photons characteristics of an element as they return to lower energy states
absorption spectrum is produced when
atoms absorb photons of certain wavelengths and become excited from lower to higher energy states
a spectrometer is used to measure
the concentration of a substance in a solution
absorbance –
the amount of light of a given wavelength absorbed by a substance
absorbance is proportional to
the amount of molecules
Bohr proposed that
electrons move in a fixed orbit
atomic orbit
mathematical description of the electron’s matter-wave in three dimensions
n represents
the principle quantum number
the principle quantum number indicates
the relative size of the orbital and therefore the relative distance from the nucleus
l represents
angular momentum quantum number
angular momentum quantum number indicates
the relative shape of the orbital
ml indicates
the magnetic quantum number
the magnetic quantum number describes the
3D orientation of the orbital
the atoms levels are given by the
n value
the atoms levels are divided into sublevels that are given by the
l value
l = 0 is what sublevel
s
l = 1 is what sublevel
p
l = 2 is what sublevel
d
l = 3 is what sublevel
f
No more than ____ electrons can be in an atomic orbital.
2
Pauli Exclusion Principle
No two electrons can have the same set of quantum numbers.
Aufbau Principle
The procedure in which electrons are assigned to orbitals.
Atomic Size is related to
the distance between atoms in a sample of the element
For the main group elements, atomic size generally
Increases going down a group due to the larger number of outer (valence electrons)
Decreases going across a period due to the larger effective nuclear charge
Ionization Energy
The energy required to remove an electron from an atom in the gas phase.
Ionization energies general
general increase across a period due to the increase in effective nuclear charge
decrease down a group due to the increase in size

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