Chem 1032 Exam 1

boiling point

Endothermic process when thermal energy is greater than the IMFs and breaks the bonds causing a boil (Pvap=Pext) As IMFs increase in strength the boiling point is higher.

vapor pressure

Tells us how many molecules are able to escape a liquid at a given temperature. Pvap is lower when stronger IMFs are present

enthalpy of vaporization (ΔHvap)

The amount of energy that is needed to vaporize the molecules, when strong IMFs are present then more energy is needed to break the bonds

Clausius-Clapeyron equation

an equation that displays the exponential relationship between vapor pressure and temperature. ln(p2/p1)=(-HΔvap/8.314J/molK)(1/T1-1/T2)

ion-dipole forces

the force that exists between an ion and a neutral polar molecule that possesses a permanent dipole moment. Strongest IMF

solute-solute interactions

must be overcome to disperse these particles when making a solution

solute-solvent interactions

"like dissolves like"

the stronger the solute - solvent interaction, the greater the solubility of a solute in that solvent

solvent-solvent interactions

must be overcome to make room for the solute

Solubility gas Rules

As temperature increase solubility decreases

As pressure increase gas solubility increases

Molality

moles of solute/kg of solvent

colligative properties

Properties of solutions, such as vapor pressure lowering, freezing point depression, boiling point elevation, and osmotic pressure, that are affected only by the number of solute particles dissolved and not by their chemical identities.

boiling point elevation

difference between the boiling point of a solution and the boiling point of the pure solvent. ΔTb=iKbm

freezing point depression

The difference in temperature between a solution's freezing point and the freezing point of its pure solvent. ΔTf=iKfm

van't Hoff factor

- total # of of particles in solution

- Ex: glucose is 1

- Ex: NaCl is 2 (breaks up into 2 ions)

Condensation

Gas to liquid(exothermic); temperature is increased and pressure is decreased

Vaporization

Liquid to gas (endothermic); Pressure and temperature both increase

Melting

solid to liquid (endothermic)

normal boiling point

the boiling point of a liquid at a pressure of 101.3 kPa or 1 atm

mole fraction

The ratio of the moles of solute in solution to the total number of moles of both solvent and solute

ppm, ppb

Parts per million, parts per billion. A measure of concentration; (part/whole solution)

Why does the solubility of solids increase with increasing temperature?

Higher temperatures cause more kinetic energy. Moving causes more mixing which adds more chance of IMFs developing between solute and solvent.

Gases solubility (blank) with increasing temperature because gas particles speed up and have more energy to leave the liquid (vaporize)

decreases

ΔHhydration equals

ΔHsolvent(always water)+ ΔHsolute(always ion-dipole)

-Always exothermic

Solubility of a solid (blank) as temperature and Energy (ΔHsolute) increases

increases

spontaneous process

-A process that occurs without an overall input of energy

Positive enthalpy of the universe (ΔSuniv)

-exothermic (-ΔH), (+ΔS ), (-ΔG)

nonspontaneous process

a reaction that needs additional energy to proceed; includes endothermic reactions

-(+ΔH), (-ΔS), (+ΔG)

Entropy

A measure of disorder or randomness.

(-ΔS more order) and (+ΔS more randomness)

standard entropy

The entropy of one mole of a substance under standard conditions

Standard entropy increases with phase, molar mass, and complexity

standard entropy of reaction

∆S°rxn = ∑∆S°products - ∑∆S°reactants

free energy change

the difference between the change in enthalpy and the product of the Kelvin temperature and the entropy change; ΔG=ΔH-TΔS

State Functions

Entropy, Enthalpy, and Free Energy

When the products are greater than reactants then Free energy is

positive (nonspontaneous)