Unit 3: Intermolecular Forces Flashcards
Which interaction force is the strongest between large molecules?
London Dispersion Forces
Dispersion forces increase with ______ contact area between molecules and with ______ polarizability of the molecules.
Increasing, Increasing
How does the polarizability of a molecule increase?
An increasing number of electrons in the molecule, and the size of the electron cloud.
Vapor pressure?
The pressure of the gas when a solution reaches an equilibrium of the # of particles that leave and enter the solution. The more pressure, the more molecules that become a gas.
Why are ionic compounds brittle?
When they slide amongst each other, the bonds will break since they can only bond at specific locations
Molecular solids are composed mainly of?
Solids with relatively weak intermoleculer forces.
Interstitial alloys?
Non-metalic, low electronegativity atoms that disrupt the flow of electrons inside the electron cloud.
The solid and liquid phases for a particular substance typically have _____ molar volume since _______?
Similar, the molecules are always in close contact with each other in both phases.
Ideal gas law?
PV = nRT
Partial pressure of one component inside a gas full of many components?
P_a = P_total * X_a, X_a = moles A/total molecules, P_total = total pressure of the gas
Total pressure of gas: P_total = ?
P_a +P_b + … + P_n
Kinetic Energy Formula?
KE = (1/2) mv^2
Axis in Maxwell-Boltzmann distribution graph?
Independent: Energies/Velocities
Dependent: Temperature
Chromatography?
(Paper, thin-layer, and column) separates chemical species by the differences in intermolecule forces strengths within species.
When are two substances more soluble and miscible?
When the intermolecular forces have similar properties (polar - polar interactions), but not (polar - non-polar interactions).
Photoelectric Effect?
When an atom or molecule absorbs or emits a proton and its energy increases or decreases by the energy of the photon.
Equation for Photoelectric Effect?
c = lambda nu, c = speed of light, nu = frequency
Energy of a photon is related to the frequent of the electromagnetic wave: Planck’s equation?
E = h nu, h = planck’s constant
In a sigma bond, the electron density is concentrated where?
Along the line connecting the nuclei.
In a pi bond, the electron density is concentrated where?
around the line connecting the nuclei.
Internuclear axis?
the line connecting the nuclei
Rules abt pi bonds? 4*
*Pi bonds are weaker than sigma bonds
*in almost all cases, single bonds are sigma bonds
*A double bond consist of one sigma and one pi bond.
*triple bond consist of one sigma and two pi bond
Hybridization?
When subshells merge and the energy state average.
Hybrid orbital?
A new orbital from hybridization.
Number of electrons in sp^x?
1 + x
Max hybridization configuration?
sp^4
Formal charge?
Charge of an atom will have if all the atoms in the molecule have the same electronegativity.
How to compute formal charge for an atom?
*All lone paired electrons are assigned to atom on which they are found.
*for every bond, half of bonding electrons are assigned to each atom in bond.
*Subtract: # of Valence electrons in the neutral atom - # of electrons that an atom has
Sum of all formal changes =?
Total charge of the molecule
How to use formal charges to determine Louis structure?
*Dominant Louis structure is generally the one in which atoms make sure that formal charges are closest to 0.
*The dominant atoms are which negative charges reside on more electronegative atoms.
Resonance structure?
Several different ways to categorize a Louis structure for the same molecule. So, each possibility gets averaged out into a symmetrical Louis structure.
Chromatography?
An experimental technique by analyzing the changes of colours.
Spectrophotometer?
Used to determine the spectrum of a compound or to determine concentration of unknown sample.
How to use spectrophotometer?
•Wavelength of light is to be used for the measurement is selected by adjusting the wavelength dial.
•Zero the meter with a reagent blank, which contains same amount of all reagents and solvents used to prepare sample.
•Reagent blank is replaced by actual sample and meter is read. More samples can be measured as long as wavelength if not changed.
-To figure out the concentration of the solute, we need to determine the wavelength of the largest peak of absorbance. The graph that plots absorbance in respect to wavelength is called the calibration curve.
Bear’s law curve?
Absorbance in respect to concentration (mM millimolar). It is a linear relationship.
Beer’s law?
Absorbance (A) = abc
Or
Absorbance (A) = epsilon bc,
Epsilon = molar absorptivity, b = path length, c = concentration
