Module 10 Flashcards
Calculate volume percent composition
((volume of component) / (total volume of soln)) * 100%
If there’s an impurity in a solution
-add to increase boiling point
(boiling pt elevated)
-substract to decrease freezing point
(freezing pt depressed)
Finding freezing/boilling point
Use eqn:
(d)T = Km
m= molality
(d)T = Difference in temperature of boiling/freezing point
K = constant
Then 0 degrees C
+ (d)T if boiling point
- (d)T is freezing point
molality
m = moles solute / kg of solvent
Osmotic pressure
pressure of a solution required to stop osmosis
pi = MRT
pi = osmotic pressure
M = molarity
R = gas constant (in Kelvin) = 0.08206
T = absolute temperature (Kelvin)
Osmosis should be in atm.
Electrolyte solution and particles
Electrolytes dissociate in solution, thus there are more particles in a solution than molecules
van’t Hoff factor (i)
i = (# of particles in solution after dissociation) / (number of formula units dissolved in soln)
i = pi / (MRT)
(osmotic pressure eqn^)
van’t Hoff factor for nonelectrolytes
1
mass/volume percentages are always implied to be?
g/mL
When gases are dissolved in a liquid solvent, what can change their solubility?
Higher temperature - solubility decreases
Higher pressure - solubility increases
When solids/liquids are dissolved in a liquid solvent, what can change their solubility?
Higher temperature - solubility increases
Higher pressure - n/a
mass percent composition eqn
(mass of element / mass of whole molecule) * 100
mole fraction eqn
i (mole fraction) = (moles of i) / (total moles)
ALSO:
using delta_Pressure = molefraction_solute * initialP_solvent
molefraction_solute = delta_Pressure / initialP_solvent
molality eqn
(moles of solute) / (kg of solvent)
ALSO:
delta_T / constant = molality
Freezing point depression
delta T
Tinitial - T_final = delta_T
Henry’s Constant
k = c/P
k = Henry’s Constant
c = concentration of solute / 1 atm
P = 1 atm
Finding solubility given partial pressure
c = kP
k = Henry’s constant (calculated w/ concentration / 1atm)
P = given pressure
Vapor Pressure of Solution
= (mole fraction of solvent) * (original pressure of solvent in mmHg)
Note: mole fraction of solvent = moles of solvent / (moles of solvent + solute)
Note: solvent can be replaced with any other kind of molecule, not just solvent
Finding moles of solute w/ mole fraction
n_solute = (mole fraction of solute * moles of solvent) / (1 - mole fraction of solute)
Partial pressure
= mole fraction * initial pressure
Find freezing/boiling point
- delta_T = constant * molality
- add/subtract delta_T from initial boiling/freezing pt
moles eqn for an element in a molecule
mol = (% of element) / atomic wright of element
Molecular Formula
- Find empirical formula
- Divide molecular mass by mass of empirical formula
- Multiply coefficients of empirical formula by the quotient
