AP Chem Ch 6-7 Flashcards
Ozone
O3 is very harmful. 10-50 km above the earth. O2 reacts with a photon to produce O3. Then O3 reacts with O3 to produce O2 and energy, increasing the temperature in the stratosphere
Collecting gas over water
Pressure of gas = pressure of room - pressure of water vapor at given temperature
Then use PV=nRT to get moles given volume
Energy
The capacity to do work or produce heat
Law of Conservation of energy
Energy cannot be created or destroyed. It is transferred. E total is constant in the universe.
Potential energy
Due to the position or composition
Kinetic energy
Due to motion.
Heat
Involves the transfer of energy between two objects due to temperature difference.
Temperature
Average KE. property that reflects random motion of particles
Work
Force acting over a distance
Change in energy = ?
Delta E = W + q
State function
Property that is independent of path. Doesn’t matter the order to get there.
Energy/heat/work state function?
Energy is a state function. Path independent.
Heat and work are path dependent. The path does matter.
This shows there are different pathways to get to the same value–> Hess law.
Exothermic
Generating/ producing heat energy. Delta E is negative. Heat is released.
Endothermic
Heat is absorbed. Heat absorbation. Delta E is positive.
Poentitial energy diagram
Shows the progression of the rxn vs the PE. if the products below the reactants then delta E is neg and exothermic.
If products above reactants then delta E is positive and enedotheermic.
If a system does work, then work is …
NEGATIVE
If work is done on a system, then work is…
Positive
Expansion/compression
Expansion has volume going up. Gas does work. So work is negative.
Compression has surroundings doing work on the gas so volume goes down. So work is positive
Volume and work relationship
W = - pressure * delta V
Volume up, work down.
Volume down, work up
Ex. Calculate delta E of a system undergoing an endothermic process in which 15.6 kJ of heat flows and where 1.4 kJ of work is done on the system
Work done on the system is positive.
Delta E = q + W. Add the values
Enthalpy
H
= E + PV
Delta H = qp = mc delta T at constant pressure.
Change in enthalpy is equal to the energy flow of heat at constant pressure.
When delta H is positive
Endothermic
When delta H is negative
Exothermic
Delta H rxn = ?
H products - H reactants
Calorimetry
Science of measuring heat
Heat capacity
Describes heat energy required to increase the temperature by one degree.
Specific heat capacity
Heat energy required to increase the temperature of one gram of substance by one degree Celsius.
J/degree c * gram
If the temperature of water goes up, why is delta H negative in a calorimeter problem
Temperature goes up in the surroundings so thus heat is released as water absorbs the heat yet it leaves the solution. Delta H is negative
Extensive property
Depends on amount of material present. Something involving mass or volume
Intensive property
Amount of substance doesn’t affect it. Such as density
What happens in a constant volume situation?
No work is done. So the delta energy = qv
Rank these from most positive delta E to most negative delta E
A. Spring is compressed and heated
B. Compress spring expands and is cooled.
C. Spring is compressed and cooled
D. Compressed spring expands and is heated
A. Is the most. Volume goes down so work is positive. Heated so q is up. Delta E = q + W so since both positive it is the most positive.
B. Is the least. Volume up so work down. Heat down.
C and D you don’t know bc depends on how much it’s increased by.
Hess’s law
Standard heats of formation = sum of the products - sum of the reactants’ heat of formation.
Standard heat of formation at what temperature?
25 degrees Celsius
Isoberic
Pressure is constant
Isochloric
Delta V = 0
Ex. Decomposition of CaCO3 (s) in limestone is used industrially to generate CO2.
CaCO3 (s) –> CaO (s) + CO2 (g)
Heat of formation = 571 kJ
Assume constant external pressure
Delta H = delta E + P delta V PV= nRT P delta V = delta n RT = (1 mol of gas - 0)(8.314)(298) = 2.5 kJ 571 = delta E + 2.5 Delta E = 568. KJ
Electromagnetic Radiation
A way for energy to travel through space. The transfer of light energy
Rankings of different rays from highest energy to lowest energy
Gamma rays X rays UV rays Visible light (VIBGYOR) Infared Microwaves Radio waves
Relationship between energy, frequency, and wavelength
Energy and frequency are proportional
Wavelength and frequency are inversely properitional
Wavelength and energy are inversely proportional
What has the lowest wavelength
Highest energy
So that would be gamma rays
What has the highest wavelength?
Lowest energy
Radio waves
Relationship between wavelength and frequency
c= wavelength * frequency
Where c is the speed of light in a vacuum, 3.0*10^8 m/s
Wavelength (lambda)
The distance between two identical points on a wave. Easiest to measure from a trough to a trough or a crest to a crest
Measured in meters- visible light in nano meters - 10^-9 m
Frequency (f or the Greek v)
The number of oxidation per second.
In 1/second, of Hertz
Speed of light
C, 3.0*10^8 M/s
All light travels at same speed in a vacuum
Planck’s constant
6.62610^-34 Jsec
Energy and frequency relationship
E=nhf
Where n is an integer, h is planks constant, and f is frequency
What does the energy frequency relationship show us?
Energy is not continuous, but it is quantized. Jumps as n increases by an integer amount rather than being able to be any value, it has specific values that it can be
Photon
A packet of energy
Photoelectric effect
Phenomenon in which electrons are emitted from a metal surface when light strikes it.
What does the photoelectric effect depend on?
Frequency and wavelength, NOT intensity. Must be over the threshold energy to eject the electrons.
Photoelectric effect key requirements:
- If frequency is varied, studies show that no electrons are emitted below a specific threshold frequency, f not
- Light with frequency lower than the threshold frequency – electrons are not emitted regardless of the intensity
- Light with frequency greater than or equal to the threshold frequency emits electrons – as the intensity of light increases, the number of electrons emitted increases as well.
- Light with frequency greater than or equal to the threshold frequency– the kinetic energy of the emitted electron increases linearly with the frequency of light.
Mass and energy relationship
Energy in light = the threshold frequency (ejection) + excess energy
This excess energy is kinetic energy which = hf-hf not
E= m c squared
So we solve for mass, m= E/c^2
Energy = hf and f=c/lambda, so E = hc/lambda
So, mass = h/lamba c
M = h/ (lambda c)
Energy has mass in the relativistic sense (not classically). Thus, energy is a wave and particle
What does energy having mass show us
Wave and particle
De Broglie equation
Wavelength = h/mass* velocity
Replace c with velocity in general– allows us to compare wavelengths of electrons with balls. The wavelength of a ball is incredible small
What’s de broglie explain
All matter can be thought of as both particles and as waves
Diffraction
Light scattering from a regular array of points or lines. Allows for the separation of electromagnetic radiation
Constructive interference
When the peaks match the peaks of the waves, reinforces the wave
Destructive interference
The peak of the wave matches the trough, canceling it out
Crystal Latrice
Solid state of matter with regular array pattern– hit x rays to generate a diffraction pattern.
This pattern supports electrons moving as waves
Atomic emmision spectra
Energy added to a system, so electron gets excited, and then it emits a photon– this results in the emission spectrum of the hydrogen atom with lines for specific wavelengths but not all values, thus it is quantized.
What happens when Hydrogen goes to the excited state?
Energy is added to the system, making the Hydrogen excited. Then goes back to the ground state, emitting or releasing the same amount of energy that was originally abosrobed. This happens when the energy of the final state - energy of initial state is negative.
Goes from excited to the ground state
When from ground to excited, it absorbs the photon of
Transitions in energy levels that are visible
All ending at n=2–> n=6–>n=2…
Bohr model
Change in energy = -2.178 *10^-18 J ((1/n2 ^2) - (1/n1 ^2))
Only works for hydrogen because one electron
N is the energy level
Predicted circular model
Standing wave
Has fixed ends –> n has to be an integer to have standing waves, which is important so that the wave can come around and get back to where it was without distructive interference causing the wave to get cancelled out.
Wave function equation
H hat (triton) = E (triton) H hat is an operator-- set of allowed mathematical instructions E is total energy of the system, PE+ KE triton is the wave function-- basically the orbital, where the electron is Triton squared is the probability of finding an electron near a particular point in space.
Wave function squared probability example
Say we have two positions in space–> (x1,y1,z1) and (x2,y2,z2)
Relative probability of finding the electron at positions 1 and 2 is given by substituting the values of x, y, and z for the two positions into the wave function, squaring the function value, and computing the following ratio:
(Triton (X1,y1,z1))^2 / (triton (x2,y2,z2))^2 = N1/N2
N1/N2 is the ratio of probabilities of finding the electron at positions 1 and 2. If the ratio were 100, then the electron is 100 times more likely to be found at position 1 than position 2
Electron density and electron probability relationship
They’re the same!
This explains what the orbitals look like
What happens to the electron probability as the distance from nucleus increases?
1/x format. Probability goes down as distance increasss
Node
When wave crosses the origin. Electrons can’t be there
N=3, 2 nodes. Has n-1 nodes.
Cut off atomic radius significance
Cut off atomic radius at 90%–> size of an orbital is arbitrarily defined as the surface that contains 90% of the total electron probability
Quantum numbers
4 QN’s that explain where we can find the electron
4 QN’s
- Principle QN (n)
- Angular momentum QN (l)
- Magnetic QN (ml)
- Spin QN (Ms)
Principle QN (n)
The energy level. Integer (1,2,3…)
Increases further from nucleus
Angular momentum QN (l)
From 0--> n-1 If n = 1, then L=0 If n= 3, then L = 0,1,2 0 = s 1=p 2=d 3=f 4=g
Magnetic QN (ml)
Ranges from -L to positive L
If l is 1, then -1,0,1
Spin QN (Ms)
Positive or negative 1/2
Pauli exclusion principle
No 2 electrons can be in the same spot in the same system
S orbital shape and reason
In the S orbital, there is only one posibility for ml, 0, and Ms can be +/- 1/2. So in a sphere shape. Two electrons in the sphere.
P orbital shape and reason
P orbital is a dumbbell. 3 different possibilities with 2 electrons in each since ml can be -1,0,1
Phosphorus electron config
1 s2 2 s2 2 p6 3 s2 3 p3 Or [Ne] 3s 2 3p 3
Valence electrons
All the electrons not in the noble gas config.
Photoelectron spectoscopy
Ability to measure the KE of an electron in the photoelectric effect and thus measure the ionization energy.
Photoelectron spec big equation
KEphoton = KE electron + IE
Ionization energy
Energy required to remove an electron
Energy associated with the reaction:
Metal–> M+ + e-
Ionization energy
Energy required to remove an electron
Energy associated with the reaction:
Metal–> M+ + e-
Ionization energy graph
More ionization energy to remove energy levels closer to the nucleus. Relative number of electrons vs ionization energy
Ionization energy graph
More ionization energy to remove energy levels closer to the nucleus. Relative number of electrons vs ionization energy
What can ionization energy diagrams tell us
Explains what atom it is based on electron relative height in the last column to the right.
Also tells us how to understand the electron structure of elements and the energy levels. 1s on bottom because most energy is required to remove a 1s electron
What can ionization energy diagrams tell us
Explains what atom it is based on electron relative height in the last column to the right.
Also tells us how to understand the electron structure of elements and the energy levels. 1s on bottom because most energy is required to remove a 1s electron
Aufbau principle
Fill lowest energy orbital first
Aufbau principle
Fill lowest energy orbital first
Hund’s rule
First fill the electrons unpaired and then pair them
Hund’s rule
First fill the electrons unpaired and then pair them
