AP Chem Final Flashcards
What is STP?
Pressure = 1 atm
Temperature = 273 Kelvin
What is important when using ideal gas law?
Pressure is in atmospheres
Temperature is in Kelvin
Volume is in Liters
How do you convert Celsius to Kelvin?
Temperature in Kelvin is Equal to Temperature in Celsius plus 273.15
How do you convert atmospheres to torr and mmHg?
1 atm = 760 torr = 760 mmHg
1 torr = 1 mmHg
What are the conversions you need to know?
2.54 cm = 1 inch
1 kg = 2.2 lbs
What is the 1 mol equal to?
6.022*10^23
What is the ideal gas constant for Kelvin and Atmospheres?
0.0821
What are the names of the equations and the variables of ideal gas law they involve?
Boyle’s Law: P, V
Charle’s Law: V, T
Gay-Lussac’s Law: T, P
Combined Gas Law: P, V, T
Avogadro’s Law: V, n
Ideal Gas Law: P, V, n, T
What is the law you utilize when there is more than one gas in a chamber?
Dalton’s Law
Total Pressure = Pressure of Gas 1 + Pressure of Gas 2 + etc
How do you find the mole fraction of a specific gas in a mixture?
Moles of the Gas/Total Moles
How do you find the pressure of a specific gas given total pressure?
Mole Fraction of the Gas * Total Pressure
What are the three postulates of KMT?
The combined volume of all molecules is negligible relative to the total volume of the gas
The average kinetic energy of molecules in a gas is proportional to the absolute temperature
All collisions are completely elastic (energy can be transferred but not lost, gas will not slow down on its own)
How does heat effect particle speed
The hotter the gas the faster the molecules within it.
What is pressure according to KMT?
Molecules in gas hitting the sides of a container
How does molar mass effect speed?
The higher the molar mass the slower the particles are
What is true of gasses at the same temperature?
They have the same kinetic energy
When does KMT/ideal gas law break down and why does this happen?
Extremely low temperatures or Extremely high pressures
Cause particles DO have volume and DO exhibit intermolecular forces
What factors affect solubility?
Temperature:
Increases solubility of solids
Decreases solubility of gasses
Pressure:
Increases solubility of gasses
What is henry’s law?
C = kP where P is the partial pressure of the gas, k is the henry’s law constant, and C is the concentration of the dissolved gas in equilibrium (in molarity aka mol/liter)
What are the types of energy?
Work: Change in Energy
Kinetic Energy: Energy from motion
Potential Energy: Due to position of composition
Thermal Energy: Associated with temperature
Chemical Energy: Associated with positions of electrons and nuclei
What is an important law for when working with energy?
Conservation of Energy
What is the system and the surroundings?
The system is the objects currently at play
The surroundings are thing outside the system which energy from inside the system gets transferred to
How do you convert from calories to Joules?
1 cal = 4.184 Joules
What are path and state variables?
State variables are the same no matter the path taken
Path variables depend on the path taken
How do you convert from L*atm to J?
1 L*atm = 101.3 J
What is the equation for work related to pressure and volume?
w = -P*ChangeV
Where P is the pressure and V is the change in volume
What are q and w for a system?
Q is the thermal energy
Positive means the system gained thermal energy, negative means the system released thermal energy aka the surroundings gained thermal energy
W is the work
Positive means work was done on the system and negative means work was done by the system
What is change in E for systems problems?
The change in the energy of the system.
Positive means energy flows into the system
Negative means energy flows out of the system
What are the equations that relate energy and temperature?
q = CchangeT
Where C is the heat capacity and changeT is the change in temperature
q = mcchangeT
Where m is mass in grams, c is the specific heat capacity and changeT is the change in temperature
q = MC*changeT
Where M is the number of moles, C is the molar heat capacity, and changeT is the cchange in temperature
How do you solve a problem involving two systems heat capacity equations?
q1 = -q2
m1C1changeT1 = -m2C2changeT2
Tf is the same for both so
m1C1(Tf - T1i) = -m2C2(Tf-T2i)
m1C1Tf + m2C2Tf = m2C2T2i + m1C1T1i
What are general trends in specific heat capacity?
As you go the left specific heat increases and as you go up specific heat increases
What is the energy of a reaction calculated as?
changeE = q + w
How do you measure the energy of a reaction in a bomb calorimeter?
Since volume is constant q is the only relevant factor
Thus
ChangeE = C_calorimeter*changeT = q
q_calorimeter = -q_rxn
What is the enthalpy?
Enthalpy = changeH = q = mCT
So enthalpy is just the heat lost or gained by the system
Notably this is different than changeE the change in energy cause it ignores the change in volume
What are exothermic vs endothermic reactions?
Exothermic reactions release energy (thus has negative enthalpy) while endothermic reactions absorb energy (thus has positive enthalpy)
What is H_rxn?
H_rxn is the enthalpy for a balanced chemical equation
So if the equation is
C3H8(g)+5 O2(g)→3 CO2(g)+4 H2O(g) and ΔHrxn=−2044 kJ
That implies for every 1 mol of C3H8 and 5 mols of O2 that is reacted to for 3 mols of CO2 and 4 mols of H20 2044kJ are released from the system.
How do you utilize a coffee cup calorimeter to find Hrxn?
-q_soln = -mCchangeT = q_rxn = q_p
H_rxn = q_p/mols of reactant
MAKE SURE TO UTILIZE NEGATIVE
What happens if you reverse a chemical reaction? what if you have enough reactants to do it twice?
It reverses the H_rxn aka it multiplies the value by -1
the H_rxn is doubled
How do you calculate H_rxn using standard heats of formation?
H_rxn = H_products - H_reactants
How do you find change E for a coffee cup calorimeter?
First find the calorimeter constant using water (if the problem requires). Enthalpy is equal to q_soln + q_calorimeter if it does and just q_soln if it doesn’t
Then changeE = Enthalpy + PchangeV
What is the speed of light in m/s?
3*10^8 m/s
What is amplitude wavelength and frequency?
Amplitude is the height of peaks of a light wave, wavelength in the distance between two peaks, frequency is the number of cycles which occur per second.
What is the relationship between frequency and wavelength?
Frequency = Speed of Light / Wavelength
What are interference and diffraction?
Interference is the process by which waves either amplify or destroy each other.
Diffraction is the process where waves going through a slit similar in size to their wavelength bend around it.
What is the energy of a photon?
E = hv
What is Planck’s constant?
6.626*10^-34 J s
Who found the photo-electric affect?
Albert Einstein
Who found black-body radiation?
Max Planck
Who found line spectra?
Niels Bohr
What is the order of the electromagnetic spectrum?
Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma Ray
What is the range of values for visible light in wavelength? Where in the rainbow does it start and where in the rainbow does it end?
750nm-400nm
750nm is red and 400nm is violet
What is a wave function?
A wave function describes the wavelike motion of an electron
What are the 4 quantum numbers and how do you find them?
n: The principal quantum number
The level of the electron (so 1, 2, 3, 4 (use periodic table))
l: The angular momentum quantum number
The sublevel of the level you are currently in (so s, p, d, f (use periodic table once again(s is considered 0)))
m_l: Magnetic quantum number
The position within the sublevel
Imagine the sublevel with the correct number of boxes (2 electrons per box). The center box is 0, to the left is -1 and to the right is +1 and etc. m_l is this number
m_s: The spin quantum number
The direction of the electron arrow. Up means +1/2 down means -1/2
What is the energy for a given n-level of hydrogen?
E = -2.18*10^-18J/n^2
How do you calculate the energy of a photon emitted from a electron falling from a higher level to a lower level?
changeE = E_f - E_i = -2.18*10^-18(1/nf^2 - 1/ni^2)
energy of photon = -changeE
What are the shapes of the first 4 orbitals?
s: Circle
p: 2 Balls connected at the middle
d: 4 Balls connected at the middle or a vertical p orbital with a ring
f: 8 Balls connected in the middle or 2 balls with rings on the ends
What are three issues with the bohr model?
Spectra Splitting
Fixed Positions of electrons
Fails for multielectron systems
What is debroglie’s wavelength equation for an object?
Wavelength = Planck Constant/Mass of the object * velocity of the object
What is determinate vs indeterminate physics?
Determinate physics says equations can predict the future
Indeterminate physics says that the future is a matter of statistics, with each possible outcome having a different percent probability
What is a property of electron’s velocity and position?
They cannot both be known at once
What is deBroglie’s hypothesis?
Electrons can demonstrate wave properties because they are in a superposition of both states, thus interfering with themself
What is electron shielding and penetration?
Electron shielding is where inner electrons apply a repulsive force to outer electrons and thus the charge exerted on them is less
Penetration is the process by which these electrons go lower than the shielding electrons and thus are not repelled as much
How many electrons can be in each orbital?
at most 2. If there is 1 it is unpaired and if there are 2 they are paired
How do you show electron configuration?
The n level followed by the sub level with the number of electrons in it shown as a superscript of the sublevel. Put them in order of energy level when writing out the configuration for an atom
What are the principles of electron filling?
Aufbau: Start from lowest energy orbital and work up
Pauli’s Exclusion Principle: No two electrons can spin the same way in the same orbital
Hund’s Rule: Electrons will first fill a sublevel spinning in parallel before then pairing in their orbitals
How do you read the periodic table to show orbitals?
For each row go 1, 2, 3, 4. Then use the left block as s, the right block as p, and the middle block as d. Remember the middle block is offset one, so on row 4 it’s n will be 3.
What are the trends in atomic radii, ionization energy, electron affinity, and metallic character?
Atomic Radii: Decreases across the table, increases down the table
Ionization Energy: Increases across the table, decreases down the table
Electron Affinity: Decreases Across the table, not definite pattern down the table
Metallic Character: Decreases across the table, increases down the table
How do you figure out electron positions for electron configurations for cations and anions?
For anions it is the same as when filling normally
However, for cations, electrons are pulled from the highest n-level rather than the highest energy level
so [Ar] 4s^2 3d^3 would pull from 4s^2 rather than 3d^3 when making the cation.
How do successive ionization energies compare to first ionization energy?
They are almost always greater
When does an atom have and not have magnetic properties?
When an atom has unpaired electrons it is paramagnetic meaning it exhibits magnetic properties
When an atom has all paired electrons it is diamagnetic meaning it does not exhibit magnetic properties
What are the three right most groups going from right to left?
Halogens, Chalcogens, Pnictogens
What are trends in atomic radii for cations and anions?
Anions are larger than the base molecule and cations are smaller than the base molecule
What order do electrons occupy orbitals?
Lowest energy first (so 1s has the lowest energy, with every successive level/sublevel being higher energy)
How do you draw a lewis dot symbol?
Right the shorthand for the element surrounded by a number of dots equal to the number of valence electrons the molecule has
What is the octet rule?
The most stable position is when a molecule has a full 8 valence electrons, and thus it is beneficial for it to obtain that state
What are the three types of bonding and the electron configuration they have?
Ionic: Electrons transferred from one molecule to another
Covalent: Electrons shared between the molecules
Metallic: Electrons pooled in between all the molecules
How do you draw the lewis structure for an ionic compound?
Have the cation sitting without any dots around it and the appropriate superscript, and then the anion in brackets with all the dots inside the brackets and the proper superscript outside the brackets
What is lattice energy?
It is the additional energy that is created by ionic compounds forming a lattice structure
How do you calculate lattice energy using the born-haber cycle?
Lattice Energy = Heat of Formation for the two substances - every other energy in the cycle
What are trends in lattice energy?
The larger the atomic radius the smaller the lattice energy
The greater the charge difference the larger the lattice energy
How do you find the lewis structure of a molecule?
Sum the number of valence electrons. Then place the center atom surrounded by all other atoms. Make single bonds with each, and place the rest of the electrons around the outer elements. Form double and triple bonds as needed to complete octets
How do you determine type of bond based on electronegativity difference?
Pure Covalent: 0 - 0.4
Polar Covalent: 0.4 - 2.0
Ionic: 2.0+
What are the 4 important electronegativity values?
F (4.0), Li (1.0), H (2.1), and Cs (0.7).
What are trends in electronegativity?
As you go across a row it increases and as you go up a column it increases
What are resonance structures?
They are all the equivalent forms a molecule can take.
How do you calculate formal charge of an atom in the lewis structure?
Original Number of Valence Electrons - 1/2 * number of bonding electrons - number of nonbonding electrons
What are some rules for formal charge?
The formal charge of the central atom should NEVER be negative. If it is find a different structure.
Formal charge should never be greater than 1, maybe 2.
Lewis structures will rearrange themselves to follow the above rules, so always check
What are the exception to the octet rule and how do you draw them?
Expanded Octet: Occurs for third row and lower. Can be used to balance formal charge.
Incomplete Octet: Unlikely but possible usually with hydrogen, just sorta make the best you can out of it (usually given formal charge)
Odd Electron Species: Unlikely but possible, again just do the best you can.
How is bond length affected by bond order?
The higher the bond order the shorter the bond length
What is bond energy?
The energy stored in the covalent bonds of a molecule
How do you find heat of reaction using bond energies?
H_rxn = H_bonds broken - H_bonds formed
What is VSEPR theory?
The idea that electron groups and molecules repel each other to form the shapes of the molecules
What are the 5 shapes of VSEPR, their bond angles, and the amount of electron groups/molecules required to form them?
2: Linear: 180
3: Trigonal Planar: 120
4: Tetrahedral: 109.5
5: Trigonal Bipyramidal: 90, 120
6: Octahedral: 90
How does electron sea account for many properties of metal?
High electrical conductivity since electrons can flow about in the delocalized sea
High heat conductivity for the same reason
High malleability since there is no particular bond
What is bond angle compression caused by?
Lone pairs exerting greater repulsive force than bonding pairs
Double/triple bonds exerting greater repulsive force than single bonds
What are the molecular geometries and their conditions?
Trigonal Planar: 1 lone pair: Bent
Tetrahedral: 1 lone pair: Trigonal Pyramidal, 2 lone pairs: bent
Trigonal Bipyramidal: 1 lone pair: see saw, 2 lone pairs: T-shapes, 3 long pairs: linear (MAKE SPECIAL NOTE OF HOW THE TRIGONAL PLANAR PART OF THE STRUCTURE GETS FILLED WITH LONE PAIRS FIRST)
Octahedral: 1 lone pair: square pyramidal, 2 lone pairs: square planar
When is a bond polar vs non-polar?
When there is an electronegativity difference of more than 0.4 the bond is polar
When is a molecule polar? what is another name for this polarity?
When there is a net dipole induced by the polarities of each bond which compose the molecule. Remember vector addition for cancellation
The dipole moment
What are the valence bond theory hybridizations and their corresponding electron group quantities?
sp: 2
sp^2: 3
sp^3: 4
sp^3d: 5
sp^3d^2: 6
Double / Triple bonds count as one electron group
What types of bonds are contained within single, double, and triple bonds?
Single: 1 sigma bond
Double: 1 sigma bond, 1 pi bond
Triple: 1 sigma bond, 2pi bonds
This makes sense because if a double bond is formed you most likely have sp^2 hybridization leaving 1 unhybridized orbital and if a triple bond is formed you most likely have sp hybridization leaving 2 unhybridized orbitals
How do you use mo theory?
Count the total number of valence electrons of two molecules which are going to bond. Then, plug into the MO boxes
What is the order and number of the mo theory boxes?
Sigma 2s: 1 box
Antibonding Sigma 2s: 1 box
Pi 2p: 2 boxes
Sigma 2p: 1 box
Antibonding Pi 2p: 2 boxes
Antibonding Sigma 2p: 1 box
For nitrogen and lighter diatomics
The pi 2p and sigma 2p are swapped for oxygen and heavier diatomics
Pi bonds have 2 boxes
Sigma bonds have 1 box
2 valence electrons per box
Electrons fill lowest energy first implying the sigma 2s has the lowest energy
What is the bond order of a MO theory bond? what does it tell us?
(Num electrons in bonding MOs- Num electrons in antibonding MOs)/2
Positive bond order indicates that the molecules will bond, with higher bond order indicating stronger bond
Negative or 0 bond order indicates that the molecules will not bond
if there is an unpaired electron in the MO diagram it shows that the object is paramagnetic (so it experiences magnetic forces).
If all electrons are paired in the MO diagram it shows the object is diamagnetic
What are the 3 types of IMFs and their order in terms of strength? also what to look for when ranking them
London-dispersion forces : Weakest : Size of the molecule
Dipole-Dipole forces : Middle : Electronegativity difference / Overall dipole pull
Hydrogen Bonding : Strongest by far : Number of hydrogen bonds present
How do you find the dipole-dipole strength of a molecule?
Draw it using VSEPR then see how the electronegativity differences would pull the electron cloud
What are properties related to IMF?
Surface tension increases as IMF increases
Viscosity increases as IMF increases
How does capillary action work?
When adhesive forces make a liquid stick to the surface of an object (usually a tube), and the cohesive forces make the molecules not directly attached come with
What are the three variables that affect vaporization?
The rate of vaporization increases with increasing temperature.
The rate of vaporization increases with increasing surface area.
The rate of vaporization increases with decreasing strength of intermolecular forces.
When does vaporization occur?
Always, due to fluctuations in thermal energy present in even a uniform liquid.
What is vapor pressure?
The pressure at which dynamic equilibrium is achieved between the vaporization of a liquid and the condensation of the liquid it comes from.
When volume is changed this balance is temporarily ruined before more or less gas disolves into the liquid, returning it back to equilibrium
What are the 6 transformations a substance can undergo?
Fusion: Solid to Liquid
Vaporization: Liquid to Gas
Condensation: Gas to Liquid
Freezing: Liquid to Solid
Sublimation: Solid to Gas
Deposition: Gas to Solid
How do you find the energy required for a substance to change from x temperature to y temperature when there is a phase change
Use normal thermochemistry to find energy required for heat change, then use heat of whatever phase change to figure out energy require to change phase.
What is heat of hydration and heat of solution?
Heat of solution is the overall enthalpy required to mix two substances. It is the heat of hydration + the heat of seperating the solute particles
Heat of hydration is the combined enthalpy of seperating the solvent particles and mixing them with the seperated solute particles
How does lattice energy relate to solutions?
Enthalpy of solute is equal to -H_lattice
What are the different ways of expressing concentration?
Molarity: mols of solute/volume of solution (L) : symbol used is (M)
Molality: mols of solute/mass of solvent (kg) : symbol used is (m)
Mass Percent: Mass of solute/mass of solution * 100
Mole Ratio: mols of solute/(mols of solute + mols of solvent)
Parts by Volume: volume of solute / volume of solution
Parts by Mass: mass of solute / mass of solution
What is raoult’s law?
Vapor Pressure of Solution = mole fraction of gas * pure vapor pressure of solvent at same temperature
How do you calculate the boiling point elevation and freezing point depression due to a solute.
Molality * Boiling point elevation constant
and
Molality * Freezing point depression constant
What sets molality apart from other measures of concentration?
It is unaffected by temperature
How do you calculate osmotic pressure?
Osmotic Pressure = Molarity * ideal gas constant * temperature in Kelvin
What is the van’t hoff factor, how is it calculated, and Whow is it used?
The van’t hoff factor is a factor which applies to electrolytes dissolved in water.
It is calculate by taking the
moles of particles in the solution / number of formula units dissolved
aka it is equal to the amount of particles a given molecule dissolves into in water.
The van’t hoff factor is used in with freezing point depression, boiling point elevation, and osmotic pressure equations. so they become
T_b = imK_b
T_f = imK_f
Osmotic Pressure = iMRT
What is the beer-lambert law?
Absorbance = proportionality constant * length of tube traveled through * concentration in molarity
