Lewis Structures
How many unpaired electrons are in the ground state of a fluorine atom?
1 unpaired electron
What is the periodic trend for electronegativity
Increases as you go up and to the right
What needs to happen in order for a molecule to absorb Infrared Light?
needs to change the net dipole with vibrations of the molecule
What is a dipole
an uneven balance of electrons that create partial charges
What kind of atoms are capable of hydrogen bonding?
N, O, F atoms
How many resonance structures can be made for the molecule NO3-?
3 structures
What makes a molecule polarizable?
more electrons and more space increases the polarizability of a molecule
What needs to happen in order for a mixture to occur and why would a mixture not happen?
A-A and B-B have to be less than A-B interactions
If A-B is not stronger than A-A or B-B it will not mix
Why is this statement false? "If a molecule can hydrogen bond it is always going to be stronger and have a higher boiling point than a molecule that cannot hydrogen bond"
Even though these forces are important, polarizability plays a factor with how large the compound is.
Rank the evaporation rate (1 being highest) CH3CH2CH2CH2CH2OH
CH3CH2CH2OH
CH3CH2CH2CH3
CH3CH2OCH3
CH3CH2CH2CH3>CH3CH2OCH3>CH3CH2CH2OH> CH3CH2CH2CH2CH2OH
Draw the line structure of the following molecules and identify the functional groups
CH3CH2CH2CH2CHO
CH3CH2OCH2CH3
CH3CH2CH3Answer Key
Rank the following according to increasing electronegativity: Br, O, Cl, N, F
Br, Cl, N, O, P
Draw a PEC of a mixed and unmixed state that would not favor mixing
Answer Key
Which of the following atoms would you expect to be most polarizable: N, P, As, Sb?
Sb
Rank the following in terms of increasing boiling point:
C4H9OH
C2H5OH
C4H10
CaBr2
C4H10 < C2H5OH < C4H9OH < CaBr2
ED= Trigonal Planar
MG= Bent
Angle= >120°
•Which of the following molecules possess a molecular Dipole?
•I. PCl5
•II. CO2
•III. HCN
•IV. NH3
III/IV
Refer to Powerpoint
Answer Key
. Which of the following compounds is capable of dipole–dipole interactions? Draw each lewis structure and label the dipole arrows.
a. CH4
b. SF6
b. CO2
d. H2CO
D only
CH2F2 has a dipole moment of 1.93 D and a boiling point of –52°C. CH2Cl2 has a dipole moment of 1.60 D and a boiling point of 40°C. Why is the boiling point of dichloromethane (92º) higher than that of difluoromethane? Which of the following explains why dichloromethane has the higher boiling point?
That CH2Cl2 has a higher boiling point proves that is has stronger intermolecular attractions, even though CH2F2 has a larger dipole moment. Evidently CH2Cl2 has larger London dispersion attraction, which is more than making up for it’s smaller permanent dipole.
For the preferred structure of POCl3, what are the bond orders for the bond between P and O and between P and Cl atoms
Cl=1
O=2
refer to answer key
These molecules would mix together.
Explain what would happen if a O2 molecule was close to a HF molecule? (explain charges of each atom too)
The permanent dipole of the HF would create a temporary dipole in the O2 because depending on which way the HF was oriented, there would be different charges in the O2
•Hexane, C6H14 (mw=86) has a boiling point of 68º. Ethanol, CH3CH2OH (mw=46) has a boiling point of 78º. Mark each of the following statements as TRUE or FALSE.
•a. Ethanol must have stronger intermolecular attraction, based on its higher boiling point.
•b. Ethanol has a higher boiling point because of greater London dispersion force
•c. Both hexane and ethanol have hydrogen bonding.
•d. Ethanol has a higher boiling point due to hydrogen bonding.
A, D are true
B, C are false