Intermolecular Forces

Question 1

What are the four intermolecular forces?

Answer 1

1. Ionic
2. Hydrogen bonding
3. Dipole-Dipole
4. London Dispersion/Van der Waals

Question 2

Rank the intermolecular forces by strength (strongest to weakest)

Answer 2

1. Ionic
2. Hydrogen Bonding
3. Dipole-Dipole
4. London Dispersion/Van der Waals

Question 3

How is the strength of the intermolecular forces related to the melting point and boiling point of a compound?

Answer 3

As the intermolecular force strength increases, the boiling point and melting point increase since more energy is needed to break the bonds since they are stronger.

Question 4

Ionic

Answer 4

Ion-Ion; something from the left of periodic table from something from the right of the periodic table; strong, solid structure needs a large amount of energy to breakup

Question 5

Hydrogen bonding

Answer 5

Interaction that occurs between heteroatom (F, O, N) and hydrogen; higher number of hydrogen bonds= higher M.P. and B.P.

Question 6

Dipole-Dipole

Answer 6

polar molecules that have a permanent dipole; creates partial positive charges and partial negative charges on a molecule that are attracted to the partial positives and negatives of another polar molecule

Question 7

London dispersion

Answer 7

very weak interactions that exist between all molecules due to temporary dipoles (based on where electrons happen to be at the moment); flipping back and forth (not permanent)

Question 8

The effect of size of a molecule on number of interactions

Answer 8

Small molecules–>less surface area–>less interactions; large molecules–>more surface area–>more interactions

Question 9

The effect of branching on boiling point

Answer 9

Increase in branching–>decrease in boiling point because branching takes up more room–>less interactions between molecules–>less bonds to break–>lowering the boiling point

Question 10

Solubility

Answer 10

Like dissolves like

Question 11

Miscibility

Answer 11

the ability of something to mix with another substance

Question 12

In what kind of solvents can ionic species dissolve in?

Answer 12

polar solvents

Question 13

Non-polar molecules can have _____ bonds.

Answer 13

polar

Question 14

Determining polarity of a molecule

Answer 14

Look for polar bond (look for electronegative atoms); see if they cancel out; if they don’t–>polar molecule

Question 15

Hydrophobic

Answer 15

incompatible with water–>substance is non-polar (oil)

Question 16

Hydrophilic

Answer 16

compatible with water–>substance is polar

Question 17

Can molecules have hydrophilic and hydrophobic sections?

Answer 17

Yes