Unit 3: Intermolecular Forces

Question 1

Which interaction force is the strongest between large molecules?

Answer 1

London Dispersion Forces

Question 2

Dispersion forces increase with ______ contact area between molecules and with ______ polarizability of the molecules.

Answer 2

Increasing, Increasing

Question 3

How does the polarizability of a molecule increase?

Answer 3

An increasing number of electrons in the molecule, and the size of the electron cloud.

Question 4

Vapor pressure?

Answer 4

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.

Question 5

Why are ionic compounds brittle?

Answer 5

When they slide amongst each other, the bonds will break since they can only bond at specific locations

Question 6

Molecular solids are composed mainly of?

Answer 6

Solids with relatively weak intermoleculer forces.

Question 7

Interstitial alloys?

Answer 7

Non-metalic, low electronegativity atoms that disrupt the flow of electrons inside the electron cloud.

Question 8

The solid and liquid phases for a particular substance typically have _____ molar volume since _______?

Answer 8

Similar, the molecules are always in close contact with each other in both phases.

Question 9

Ideal gas law?

Answer 9

PV = nRT

Question 10

Partial pressure of one component inside a gas full of many components?

Answer 10

P_a = P_total * X_a, X_a = moles A/total molecules, P_total = total pressure of the gas

Question 11

Total pressure of gas: P_total = ?

Answer 11

P_a +P_b + … + P_n

Question 12

Kinetic Energy Formula?

Answer 12

KE = (1/2) mv^2

Question 13

Axis in Maxwell-Boltzmann distribution graph?

Answer 13

Independent: Energies/Velocities
Dependent: Temperature

Question 14

Chromatography?

Answer 14

(Paper, thin-layer, and column) separates chemical species by the differences in intermolecule forces strengths within species.

Question 15

When are two substances more soluble and miscible?

Answer 15

When the intermolecular forces have similar properties (polar - polar interactions), but not (polar - non-polar interactions).

Question 16

Photoelectric Effect?

Answer 16

When an atom or molecule absorbs or emits a proton and its energy increases or decreases by the energy of the photon.

Question 17

Equation for Photoelectric Effect?

Answer 17

c = lambda nu, c = speed of light, nu = frequency

Question 18

Energy of a photon is related to the frequent of the electromagnetic wave: Planck’s equation?

Answer 18

E = h nu, h = planck’s constant

Question 19

In a sigma bond, the electron density is concentrated where?

Answer 19

Along the line connecting the nuclei.

Question 20

In a pi bond, the electron density is concentrated where?

Answer 20

around the line connecting the nuclei.

Question 21

Internuclear axis?

Answer 21

the line connecting the nuclei

Question 22

Rules abt pi bonds? 4*

Answer 22

*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

Question 23

Hybridization?

Answer 23

When subshells merge and the energy state average.

Question 24

Hybrid orbital?

Answer 24

A new orbital from hybridization.

Question 25

Number of electrons in sp^x?

Answer 25

1 + x

Question 26

Max hybridization configuration?

Answer 26

sp^4

Question 27

Formal charge?

Answer 27

Charge of an atom will have if all the atoms in the molecule have the same electronegativity.

Question 28

How to compute formal charge for an atom?

Answer 28

*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

Question 29

Sum of all formal changes =?

Answer 29

Total charge of the molecule

Question 30

How to use formal charges to determine Louis structure?

Answer 30

*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.

Question 31

Resonance structure?

Answer 31

Several different ways to categorize a Louis structure for the same molecule. So, each possibility gets averaged out into a symmetrical Louis structure.

Question 32

Chromatography?

Answer 32

An experimental technique by analyzing the changes of colours.

Question 33

Spectrophotometer?

Answer 33

Used to determine the spectrum of a compound or to determine concentration of unknown sample.

Question 34

How to use spectrophotometer?

Answer 34

•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.

Question 35

Bear’s law curve?

Answer 35

Absorbance in respect to concentration (mM millimolar). It is a linear relationship.

Question 36

Beer’s law?

Answer 36

Absorbance (A) = abc

Or

Absorbance (A) = epsilon bc,

Epsilon = molar absorptivity, b = path length, c = concentration