Chemistry 111 - Exam 1 - IMFs & Properties of Solutions

Inter Molecular Forces (IMF)

how 2 different molecules interact and the forces between them

What are IMFs responsible for?

• physical properties

• states of matter

• reactions

Intermolecular Seporation

average distance between molecules, increases with higher energy s→l→g

Induced Dipole

only 1 atom needs a dipole moment that effects all others to also have dipoles

Dispersion

• IMF that is always present

• stronger with higher mm & atomic mass

• depends on surface area

  • if linear → more dispersion

  • if compact → less dispersion

• only attractive force

Dipole Dipole

• IMF that must have a permanent dipole

• ↑ difference in electronegativity → polar molecule → dipole dipole

• can be repulsion and attraction

• polarity ↑, dipole dipole ↑, BP ↑

Water’s Properties

1. very polar

2. weak dispersion (18 g/mol)

3. BP ↑ at 100 C

4. hydrogen bonding

5. 0 C FP - solid ice is lower density than liquid bc it leaves gaps for hydrogen bonding → floats

Hydrogen Bonding

IMF where hydrogen is covalently bonded to F, O, N

Ion Dipole

IMF within ions where positive polar pulls anions and negative polar pulls cations

Viscosity

• resistance to flow (honey ↑, water ↓)

• easy IMF to see

• IMF ↑, viscosity ↑

Boiling Point

• temperature where l → g

• IMFs ↑, BP ↑

• molecues w/ high IMFs hold on tighter → more energy to boil

Evaporation

• slow change from l → g

• at temp below boiling

• IMF ↑, evaporation rate ↓ (evap ↑ if temp ↑)

Surface Tension

IMF ↑, surface tension ↑

• regular molecules have forces on all sides, surface molecules have no upward pulling force so the downward force placed on the water doesn’t have anything to push back → further down

Cohesion

strong attraction for itself

Adhesion

strong attraction for other molecules

Vapor Pressure

the pressure exerted by vapor above a volatile (evap readily) liquid, P of vapor in equilibrium w/ a liquid

Capillary Action

water rises in a narrow glass tube without any additional forces because of cohesive forces to the glass and adhesive to the other water

Melting/Fusion

solid to liquid

Freezing

liquid to solid

vaporization

liquid to gas

condensation

gas to liquid

sublimation

solid to gas

deposition

gas to solid

Supercooling

liquid being cooled super fast that it doesn’t have time to convert to a solid

critical temperature

the highest temp where a liquid can be formed, has to be cooled below in order to turn into liquid from gas with pressure

critical pressure

pressure required to bring about liquefication of a gas at critical temperature

superficial fluid

when temp > critical temp & pressure > critical pressure, the liquid and gas states are indistinguishable, thet are extremely powerful solvents

solvent

the more abundant part of a mixture

solute

the less abundant part of a mixture

solution

homogenous mixture of solute and solvent

solute-solute forces

must be overcome to distribute the solute throughout the solvent

solvent-solvent forces

must be overcome to make room for the solute molecules to spread out

solvent-solute forces (solvation) (if water, hydration)

occur as the particles mix, the driving force behind solution formation, their IMFs are stronger than solute-solute → mixes together → greater solubility

Saturated solution

max solubility reached, no more able to dissolve

unsaturated solution

has the ability to take more solute

Solubility

amount of solute dissolved

liters of solvent

at a given temp where like dissolves like → similar IMFs between solute and solvent → greater solubility

supersaturated solution

more solute than needed for it to be saturated

solubility depends on

• P g ↑ → solubility ↑

• mm ↑ → solubility ↑

• T ↑ solubility g ↓

• T ↑ → solubility s ↑

• IMFs (like dissolves like)

mass % equation

mass of component x100%

total mass

volatile solvent

anything with BP < 100 C, lower IMFs

non-volatile solvent

anything with BP > 100 C, higher IMFs

i (van’t hoff factor)

the number of particles the solute splits into when dissolved

osmosis

• the flow of water (or solvent) across a membrane

• net movement of solvent is toward the solution with higher solute concentration bc wants homogenous

osmotic pressure

the pressure required to stop osmosis from a pure solvent to a solution

colligative properties

physical changes from adding a solute to a solvent, depend on the quantity (concentration) of solute particles and not on identity

types of colligative properties

• vapor pressure lowering

• depression of freezing point

• elevation of boiling point

• osmotic pressure

electrolytes

• solutions that conduct electricity

• ions are present

• i > 1

non-electrolytes

• no conducting electricity

• no dissociation into ions

• i = 1

isotonic

two solutions with identical osmotic pressure