77 Cards in this Set
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Calculating Standard Enthalpy Change for Reaction
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Reactions can be written reverse.
Equation-
Sum * moles * times each product- Sum * Moles * each reactant
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Nature of Light
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Light behaves as both wave and particle and depends on how you are measuring it.
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Speed of Light (c)
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3.00 x 10^8 m/s. Light travels faster than sound (lightening/thunder).
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Amplitude and wavelength
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different wavelengths, different colors. Different amplitudes, different brightness.
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Characterizing Waves
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Long wavelength: Low frequency, low energy.
Short Wavelength: High frequency and high energy.
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Frequency
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Number of crests of waves of same wavelength that pass by a point in one second, same amount of time.
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Equation for frequency (V)
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V= c
λ
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one m (distance)
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10^-9 nm
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What determines color?
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Frequency and wavelength.
White mixture of all wavelengths in the visible region.
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Red
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Longest wavelength, low frequency, low energy
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Violet
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Shortest wavelength, high frequency, high energy
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How can you see color?
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Wavelengths that are not absorbed by object.
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Bees can see shorter wavelengths than humans can. What radiation can bees see?
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UV- 10^-7
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Interference
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Interaction of waves
Waves in phase: Constructive(bright spots)
Waves out of phase: Destructive(dark spots)
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diffraction
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the bending of a wave as it moves around an obstacle or passes through a narrow opening
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Particle Nature of Light
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Hertz- light shines onto metal surface causing electrons to be emitted from metal.
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Photoelectric Effect
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Wave theory predicts that use dim light to eject electrons but had to be exposing for a long time.
electrons need to be absorb to be ejected.
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Photoelectric Effect Wave Theory
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Shorter wavelength light would eject more electrons.
Lower frequency and long time= no electrons
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Einstein's explaination
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Albert Einstein: light energy must come in packets. Energy Photons depend on frequency
Photon (quantum of light) = smallest packet (particle) of light
Photon energy = proportional to its frequency (v)
Planck's Constant (h) = 6.626 x 10-34 J • s
J = kg • m2/s2
E = hv = h • c / λ
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Photons
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Shower of particles.
E= hv
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Ejected Electrons
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Photon of higher energy give electrons too much energy.
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Law of Photoelectric Effect
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KE=Ephoton-Ebinding= Hv-ψ
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Wave Particle Duality of Light
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The study of the photoelectric effect led to important steps in understanding the quantum nature of light and electrons and influenced the formation of the concept of wave–particle duality.
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1 mJ
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10^-3 J
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Photons finding Energy
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Etotal= Ephoton X number of photons
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Atomic Spectroscopy
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Study of electromagnetic radiation that is absorbed and/or emitted by atoms.
Demonstrates particle wave nature of light and identifies element (unique).
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Absorption Spectroscopy
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Molecules can absorb light and re-emit light.
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Emission Spectrum
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When that emitted light is passed through a prism, a pattern of particular wavelengths of light is seen that is unique to that type of atom or molecule.
Can identify element.
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White light Spectrum
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Continuous (no interruptions in the intensity as a function of wavelength).
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Rydberg's Spectrum Analysis
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Rydberg analyzed the emission spectrum of hydrogen.
• Found that wavelengths could be described with an equation that involved an inverse square of integers
Problem is that it doesn’t explain why atomic spectra were composed of discrete lines or why this equation even worked.
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What is rydberg's equation?
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1/λ=R(1/nf^2 - 1/ni^2)
R= 1.097*10^7
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Rutherford's Nuclear Model
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The nucleus is essentially the entire mass of the atom. The atom contains a tiny dense center called the nucleus
• The nucleus is positively charged
• The electrons move around in the empty space of the atom surrounding the nucleus
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Problems in Rutherford's model
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Electrons are moving charged particles
• According to classical physics, moving charged
particles give off energy
– Therefore electrons should constantly be giving off energy
The electrons should lose energy, crash into the nucleus, and the atom should collapse!!
– but it doesn’t!
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Bohr Model of Atom
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The electrons travel in circular orbits that are at a fixed distance from the nucleus.
– The energy of each orbit was
fixed, or “quantized”
– Therefore, the energy of the electron was proportional to the distance the orbit was from the nucleus
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Bohr's model and Emission Spectra
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Electrons absorbing photon goes up energy level.
Electron emitting goes down
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When is spectral line formed?
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when an e- falls from one
stable orbit to another of lower energy
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When does electrons emit light?
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when it "jumps" from an orbit with higher energy down an orbit with lower energy
– the emitted radiation was a photon of light
– the distance between the orbits determined the energy of the photon of light produced
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de Broglie Wavelength equation
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λ=h/mv. Particles behave like waves.
Present interference pattern.
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Uncertainty Principle
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An e- that passes through the laser will produce a flash (a photon is scattered)
• The flash originates behind one slit, never both at the same time and you get no interference pattern.
• No matter how hard we try, we cannot see the interference pattern and observe which slit the electr…
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Wave and Particle Properties
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Wave= Interference
Particle=2 lines
Can observe wave nature not particle nature.
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Heinsburg
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States that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle. He concluded that it is impossible to make any measurements on an object without disturbing the object.
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What is the equation for the uncertainty principle?
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Δx X Δv > h/m (the error in the measurement of an object's position times the error in that object's velocity must be greater than Planck's constant divided by the object's mass)
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Indeterminancy
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Do not have accuracy and can't predict.
Probability
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Electron Energy
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KE=1/2mv^2
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Schrödinger's equation
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Ηψ=ξΨ
Probability of finding electron with specific energy at same location
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What are the quantum numbers? (3)
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n-size
ℓ-shape
mℓ-orientation
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Principle Quantum number (n)
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energy of electron in orbital
Higher n=higher E
(opposite for negatives)
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Angular Momentum Quantum Number, l
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The angular momentum quantum number (l) determines the shape of the orbital
• l can have integer values
from 0 to (n – 1)
– n = 1 : l = 0. n = 2 : l = 0 and 1 . n = 3: l = 0, 1, 2
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Shape l
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l=0 (s)
l=1 (p)
l=2 (d)
l=3 (f)
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Magnetic Quantum Number, Ml
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• The magnetic quantum number is an integer that
specifies the orientation of the orbital
– the direction in space the orbital is aligned relative to the other orbitals
• Values are integers from −l to +l including zero
– When l = 2 ml are −2, −1, 0, +1, +2;
– That means there are …
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Describe Orbital
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• Each set of n, l, and ml describes one orbital
• Orbitals with the same value of n are in the same principal energy level (or shell)
• Orbitals with the same values of n and l are said to be in the same sublevel (or subshell)
– Orbital with n = 1, l = 0, and ml = 0 is known as the 1s…
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Energy Shells
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• The number of sub levels in any level is equal to n
• The number of orbitals in any sub level is equal to 2l + 1
• The number of orbitals in a level is equal to n^2
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Electrons Transition
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• To transition to a higher energy state, the electron must gain the correct amount of energy corresponding to the difference in energy between the final and initial states
• Electrons in high energy states are unstable and tend to lose energy and transition to lower energy states
– Eac…
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Which Transition has shortest wavelength?
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n=3 to n=2
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Energy
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The ability to do work
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Work
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Force acting over Distance
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First law of Thermodynamics
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Energy can neither be created nor destroyed.
Total amount of energy in Universe is constant.
Can track energy by defining system and surroundings.
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Energy Flow
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Surrounding gain exact amount of energy lost by surroundings.
ΔEuni.= ΔEsys-ΔEsurr.
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State Function
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Change in altitude depends only on difference between initial and final values, not path taken.
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Changes in Internal Energy
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ΔE=Efinal-Einitial
Only depends on how much energy you started with and how much left in system
ΔErxn= Epro.-Ereact.
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ΔE+
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Products are greater than reactants.
-ΔEsys.(gain)=ΔEsurr.(lose) Product on left side of reaction.
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ΔΕ- energy released
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Reactants on left side and greater than products. Releases energy.
ΔEsys.(lose)= -ΔEsurr.(gain)
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Heat and Work
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ΔΕ= Q+W Heat and work NOT state functions but energy is.
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Heat
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Exchange of thermal energy between system and surroundings.
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Temperature
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Measure of amount of thermal energy
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heat exchange
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Only go from high temperature to low.
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Heat capacity
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Measure of ability to absorb thermal energy without large ΔT
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Factors affect Heat capacity
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1.Depend on amount of matter
2. Depend on type of matter
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Specific heat capacity
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Intrinsic ability of matter to absorb heat energy. Cs.
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Specific heat of water
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• The rather high specific heat of water allows water to absorb a lot of heat energy without a large increase in its temperature
• Water is commonly used as a coolant because it can absorb a lot of heat and remove it from the important mechanical parts to keep them from overheating
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Heat energy
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Heat= mass X Cs (SPC) X Temp. Change ΔT
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Heat transfer/Final temperature
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• When two objects at different temperatures are in
contact, heat flows from the material at the higher temperature to one at the lower temperature
– Heat flows until both materials reach the same final temperature
• The amount of heat energy lost by the hot material
equals the amount…
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Pressure-Volume Work
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• PV work is work caused by a volume change against an external pressure
• When gases expand, DV is positive, but the system is doing work on the surroundings, so wgas is negative
W=‾PΔV
1 atm*L= 101.3 J
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enthalapy
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amount of heat a substance will hold at a given temperature.
Mass(g) to Moles to KJ.
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Measure ΔΗ
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Find Joules by Mass*Cs*ΔT then find moles then Joules divide moles to find ΔΗreaction.
qrxn.= -qsol.
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Relationships involving ΔΗ
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1. When reaction is multiplied by a factor, Hrxn is also multiplied by that factor because Hrxn is an extensive property.
2. If a reaction is reversed, then the sign of H is changed
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Hess's Law
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If a reaction can be expressed as a series of steps, then the Hrxn for the overall reaction is the sum of the heats of reaction for each step.
• We can do this because enthalpy is a state function and both reactions share the same intermediate (C).
– It is only dependent on the initial…
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CH 101: EXAM 3