Chap 1

Question 1

Intermolecular Forces
Hydrogen Bonding –
Dipole-Dipole Forces –
London Dispersion Forces (van der Waals Forces) –
Ion-Dipole Forces –

Answer 1

Question 2

Ranking Boiling Points

Answer 2

Question 3

Bond angle?

sp

sp2

sp3

Answer 3

Question 4

Do bonds other than single bonds have sigma bonds? double? triple? how many for each?

Answer 4

All single bonds are sigma bonds and the first bond of a double or triple bond is also a sigma bond. The remaining bonds are pi bonds which means that a double bond is composed of 1 sigma and 1 pi bond, and a triple bond is composed of 1 sigma and 2 pi bonds. The molecule in questions has 3 double bonds (having 3 pi bonds) and 1 triple bond (having 2 bonds) and therefore has a total of 5 pi bonds.

Question 5

What orbitals overlap to form the pi bond indicated in the structure below?

Answer 5

Question 6

Does boiling pint increase with greater intermolecular forces?

Answer 6

Yes?

Question 7

Does a greater surface area or branching create a higher melting point?

Answer 7

all alkanes, are nonpolar, and have only London dispersion forces. The greater the molecular weight and surface area, the greater the greater the London dispersion forces.

Starting with the simplest branched compound, as you increase branching, you will increase the melting point, but decrease the boiling point. Why? … Boiling point is related to the forces between molecules, which in the case of hydrocarbons is Van Der Waals interactions

Question 8

Does a greater surface area or branching create a higher boiling point?

Answer 8

With increase in the branching, the surface area of the molecule decreases and vander waals forces of attraction decreases which can be overcome at a relatively lower temperature. Hence, the boiling point of an alkane chain decreased with an increase in branching

Question 9

Under what circumstance doe solubility increase? (NOT WATER) HEXANE

Answer 9

The governing principle in solubility is “like dissolves like” in terms of polarity. Cyclohexane is nonpolar and the most nonpolar of the answer choices will be most soluble in cyclohexane.

alcohols and are capable of hydrogen bonding. The least polar will be the one with the longest carbon chain:

Question 10

Under what circumstance solubility increase in WATER?

Answer 10

alcohols and are capable of hydrogen bonding due to the presence of the hydroxyl group. The carbon chain is hydrophobic though and the longer the carbon chain the lower the polarity and the less soluble the compound will be in water. The compound that is most soluble in water will therefore have the shortest carbon chain

Branching makes carbon chain shorter ( shorter the batter)

Question 11

Does branching alkane raise the melting point?

Answer 11

Yes!

• Branching has a lower boiling point.
• Because it has a lower surface area.

BUT

1. Branching raises the melting point.
2. More compact structure=better bit crystal structure.