Chapter 5

Question 1

Solids

Answer 1

Lowest Temp, Highest IMF

Question 2

Liquid

Answer 2

In middle

Question 3

Gas

Answer 3

Highest temp, lowest IMF

Question 4

van der Waals forces,
or informally as intermolecular
attraction is

Answer 4

All the attractive forces between
neutral atoms and molecules

Question 5

London Dispersion Forces

Answer 5

Present in all condensed phases
Present for all molecules, whether
they are polar or not
Weakest IMF
Larger and heavier atoms exhibit stronger dispersion forces (polarizability of large atoms)

Question 6

A larger contact area

Answer 6

allows for more
dispersion forces

Question 7

Dipole-Dipole attraction

Answer 7

• Only present with polar molecules
• Stronger than London dispersion forces
  -Larger dipole moment = stronger dipole-dipole attraction

Question 8

Hydrogen bonding

Answer 8

• is the strongest type of dipole-dipole attraction
• higher boiling point
• F-H, O-H, or N-H bonds

Question 9

Ion-dipole interactions

Answer 9

• an ionic compound is dissolved
  in a polar solvent

The strength of the ion-dipole
interaction determines the solubility of an ionic compound in water

Question 10

Weakest to strongest INTERMFS

Answer 10

Dispersion, Dipole dipole, hydrogen bonding, ion dipole

Question 11

INTRAMFS

Answer 11

covalent, ionic

Question 12

Immiscible

Answer 12

does not mix ( lose imfs and dont gain back)

Question 13

miscible

Answer 13

mixes (lose imfs but gain them back)

Question 14

Some ionic compounds release heat when dissolved in water, some absorb
heat, others don’t have a noticeable effect on temperature, these effects are

Answer 14

the enthalpy of solution

Question 15

The enthalpy of solution (ΔHsoln) can be broken down into two parts:

Answer 15

1. Separating the ions: lattice energy (ΔHlat or ΔHsolute)
2. Hydrating the ions: enthalpy of hydration (ΔHhydr)

Question 16

lattice energy is

Answer 16

always positive, it takes energy to
separate opposite charges

Question 17

hydration enthalpy (ΔHhydr) is

Answer 17

always negative, forming
intermolecular interactions (ion-dipole) releases energy

Question 18

If ΔHsolute is greater than ΔHhydr, then

Answer 18

ΔHsoln is positive (endothermic)

Question 19

If ΔHhydr is greater than ΔHlat, then

Answer 19

ΔHsoln is negative (exothermic)

Question 20

how do greenhouse gases absorb infrared light?

Answer 20

• Light travels through the electromagnetic field and interacts with charged particles
• At high enough energy (UV or visible), light can directly excite electrons and break chemical bonds
• At lower energy (IR), light can only cause bonds to vibrate (as long as they have partial charges to
  interact with).

Question 21

So how can a non-polar molecule like CO2 absorb IR radiation?

Answer 21

there must be some combination(s)
of bond vibrations (stretches and/or bends) which change its dipole
moment (polarity), like CO2

Question 22

Water is a much more ‘efficient’ greenhouse gas compared to CO2,
because

Answer 22

it is permanently polar, which means that all its modes of vibration are IR-active

Question 23

The only molecules that do not absorb IR radiation at all are

Answer 23

homonuclear
diatomic molecules, like N2