Download When drawing Lewis Dot Structures, remember to make sure: • Your

UW CHEM 120 Autumn 2012 Name __________________________________________ Section _____________ WS 5: Dot Structures and Intermolecular Forces When drawing Lewis Dot Structures, remember to make sure: • Your structure uses the correct number of electrons • Resonance structures are included, if appropriate • The octet rule is followed, except where it shouldn’t be… o Some can have less than an octet, such as § H, which requires only 2 electrons, § B, which can have 6 or 8 electrons, and § Be, which requires only 4 electrons. o Some can have expanded octets, such as § P, which can have 10 electrons, § S, which can have 12 electrons, and § Cl, Br and I, which can have 14 electrons, (although they almost always have 8) 1. For each of the formulas below, provide the Lewis Dot Structure. CH3CH3 CH3CH2CH3 CH3CH2OH PO43-­‐ NO2+ NO2-­‐ 1 of 3 UW CHEM 120 Autumn 2012 In the following pairs, list the intermolecular force that each species exhibits, and circle the structure that will exhibit the strongest intermolecular forces. a. C3H8 and C8H18 C C CH3 C C F b. F
and F
H
H
H
C
C
C
C
O
C
C
C
H
H
H
H
H
c. benzaldehyde H
and C
C
C
C
O
C
C
C
OH
H
H
benzoic acid 2 of 3 UW CHEM 120 Autumn 2012 •
The tables below contain boiling point data for several different hydrocarbons (made of C and H only) and alcohols (a hydrocarbon with an –
OH group attached). Explain any trends you observe in these boiling points in terms of the strength of intermolecular forces. Hydrocarbons
Alcohols
Molecular
Formula
Molecular
Mass (amu)
Boiling
Point (°C)
Molecular
Formula
Molecular
Mass (amu)
Boiling
Point (°C)
CH4
CH3CH3
CH3CH2CH3
CH3CH2CH2CH3
16
30
44
58
−162
−88
−42
−0.5
CH3OH
CH3CH2OH
CH3CH2CH2OH
32
46
60
65
79
97
3 of 3