chem 1312 chapter 10,11,12

Raoult’s Law Formula

P_solution=X_solventP*_solvent

Raoult’s Law Definition

Adding a nonvolatile solute lowers vapor pressure

Raoult’s Law Application

Lowering vapor pressure connects to other colligative properties

Raoult’s Law question example and strategy

calculate vapor pressure density and mass of solute and solvent:
1) mol solute and solvent

2) mole fraction of solvent

3) calculate vapor pressure using Psolution=XsolvPsolv

(Psolv given: “water at 100*C”=water is boiling= pressure is 1.00 atm

Colligative Properties key concept

colligative properties depend on the number of dissolved particles

osmotic pressure formula

Osmotic Pressure=iMRT

van’t hoff factor

number of particles the solute breaks into in water

molarity

moles solute/ L solution

molality

mol solute/kg solvent

mole fraction

mole A/total moles

how do gas and temp affect gas solubility

• gas solubility depends on pressure

• temp affects solubility differently for solids and gases

van’t hoff factor (i) =

moles of particles in solution/moles of solute dissolved

boiling point elevation by nonvolatile solutes formula

ΔTb = i m Kb

i= vant hoff

m= molality

Kb=boiling point of constant solvent

freezing point elevation by nonvolatile solutes formula

|ΔTb| = i m Kf

i= vant hoff

m= molality

Kf=freezing point of constant solvent

• absolute value!

possible application of freezing or boiling point questions

find molar mass of solute

colligative properties

depend on number of particles

• bp, fp, osmotic pressure

• the number = molality → use for temperature (bp or fp)

Average Rate (from concentration data of reactant A):

rate law

overall order

m+n

whatever this is

zero order

[A]_f= -kt + [A]o

first order formula

ln[A] = -kt + ln[A]o

second order formula

zero order half life

[A]o / 2k

first order half life

ln(2/k) or 0.693/k

second order half life

1/k[A]o

arrhenius equation tells you

temperature dependence of the rate

arrhenius formula

k=Ae^(-Ea/RT)

linear for arrhenius equation

ln(k)= -Ea/R • (1/T) + ln(a)

Keq=

products over react and raised to stoichiometric coefficients leaving out pure liquids and solids

Henry’s law concept

describes how concentration varies with pressure

Henry’s Law formula

c=KP (concentration= constant x partial pressure)

finding units of K in rate laws

k= m^n-1 x t^-1

systematic ratio strategy

divide all runs by smallest initial rate

gas constant for arrhenius equation

8.314 s/mol*k

arrhenius equation:

increase T=

increase K

linear arrhenius formula

ln(k)= -Ea/R * (1/T) + ln(A)

temp rate comparison arrhenius equation

ln(k2/k1)= -Ea/R * (1/T2 - 1/T1)

reaction mechanism

sequence of elemnetary steps resulting in overall reaction

elementary step

a simple rxn with NO intermediates and only one transition state

rate determining step

step that is much slower than the others

Keq=

Kforward / Kreverse

Kp=

Kc(RT)^{delta n_gas}

if delta n_gas=0

Kp=Kc

K»1 the reaction is

product favored (numerator is larger)

K«1 the reaction is

reactant favored (denominator is large)

reversing reactions find K

take reciprocal of K1

what if stoichiometric coefficients change

raise K1 to power of coefficient (K2= K1^1/2)

what happens to Keq is you add a chemical equation?

adding rxns multiplies the individual equilibrium constants (K5= K1 x K4)

ICE tables

if Initial [c] of some species are known and Changes in [c] can be deduced by rxn stoichiometry, then the Equilibrium concentrations can be determined

Q>K

net flow to left (reverse reaction). means too many products

Q=K

equilibrium

Q<K

net flow towards right (products, forward reaction) means there are too many reactants