Unit 2

temp dependence of ∆S of surrounding

at high temps - surr. already have lots of thermal energy spread among many possible motions, so adding little more changes dispersal less. (small, and positive)

at lower temps - the same added energy makes a bigger difference (large, and positive)

∆°H

enthalpy change per mole substance

∆H

enthalpy changes for the whole substance amount

∆S for Surrounding equation chemical rxn

-∆H(rxn)/T = (-∆H°(rxn) ∙ moles)/T

change in ∆S (surrond) when given ∆H (system)

-∆H(sys)/T

Gibbs Free Energy formula

G = H - TS / ∆G = ∆H_(sys) - T∆S_(sys)

-∆G

spontaneous

+∆G

non-spontaneous

0= ∆G

equilibrium

chart for Gibbs free energy

third law of thermodynamics

-the entropy (S, not ∆S) of a perfect crystal at absolute zero (0 K) is 0 J/mol(K)

-exactly 1 microstate

-every other substance that is not a perfect crystal or not at absolute 0 has some energy in the form of entropy.

-the sign of the entropy of any substance at temperatures above absolute zero is always positive

first law of thermodynamics

that energy can not be created or destroyed but merely converted from one form to another

second law of thermodynamics

entropy of a system should always increase

Molarity (M)

Moles of solute/ volume of solution (L)

-molarity varies w/ temp bc temp affects the volume of a solution

Molality (m)

moles of solute/mass of solvent(kg)

Mole fraction

moles of component A/ total moles in solution

mole percent

(moles of component A / Total moles in solution ) ∙100%

volume percent

(volume of solute / total volume of solution) ∙100 %

mass percent

(mass of solute/ total mass of solution) ∙100%

parts per million (ppm)

mass of solute (mg)/ total mass of solution (kg) = (mass of solute/total mass of solution)∙10⁶

parts per billion (ppb)

mass of solute (µg)/total mass of solution (kg) = (mass of solute/total mass of solution) ∙10⁹

∆_solution for gases are always…

negative

• the solubility of any gas will always decrease as temperature increases

Henry’s law for gas solubility

S = K_H (P_gas)

what are the four colligative properties

1. vapor pressure lowering

2. freezing point depression

3. boiling point elevation

4. osmotic pressure