TEST 2- 17.1-17.7, 17.10, 11 Flashcards
First law of thermodynamics
energy cannot be created or destroyed, only transferred
The internal energy of an isolated system
remains constant
The total energy of the universe is
constant, and change in energy of universe is 0
The first law of thermodynamics describes
organized energy
Second law of thermodynamics
all spontaneous energy transfers in the universe serve to increase overall entropy (s) of universe
Reversible process
does not increase entropy of universe, can be undone by reversing conditions, can be forward or reverse on path
Irreversible process
does increase the entropy, cannot be undone
Spontaneous reaction or change
continue to occur on its own without outside forces
Spontaneous reactions will result in
increase in disorder (entropy) of universe
Spontaneous processes do not need
continuous input of energy
Nonospontaneous process
does not occur in specific conditions and requires an input of energy
Organized energy of universe
goes down, disorganized energy goes. up
The second law of thermodynamics describes
disorganized energy
Third law of thermodynamics
as temp increases so does entropy, as temp decreases so does entropy
At 0 K
absolute 0, entropy is 0
Entropy
increase in randomness or dispersal of matter and energy in J/Kxmol
Standard entropy
absolute entropy at pressure 1 atm
Microstates
all the microscopic distributions of energy among particles in a system that are possible, while maintaining the macroscopic form
Entropy related to microstates equation
S = Kbln(W)
Kb
boltzman’s constant- 1.318 x 10^-23 J/K
W
number of microstates
A decrease in pressure or increase in volume
Increases entropy
A decrease in pressure means an increase in
volume, energy has more space to disperse
Larger molecule size allows for more
microstates and greater entropy
Two substances of the same substance in same state
larger sample will have more entropy
A process with an increase in the number of gas particles will result in
overall increase in entropy
Mixing substances will cause
increase in overall entropy, solid has higher entropy when dissolved than when in solid form
Two compounds with similar mass in same phase
more complex means a greater entropy
Enthalpy in exothermic processes
enthalpy is negative, system releases energy, heat of surroundings is greater than 0, heat of system is less than 0, and ENTROPY of surroundings is greater than 0
Enthalpy in endothermic process
enthalpy is positive, system absorbs energy, heat of system is greater than 0, heat of surroundings is less than 0, and ENTROPY of surroundings is less than 0
Energy gained by the surroundings is equal to
the energy lost by the system, qsurroundings = - qsystem
Change in entropy of phase change =
change in enthalpy of change divided by temperature where change occured
Positive value of change in entropy
increase in entropy, favorable, spontaneous
Change in entropy of universe =
Change in entropy of system + change in entropy of surroundings, Change in entropy of system + enthalpy of surroundings / temp
Change in entropy surroundings =
- Change in enthalpy system / Temp at constant pressure
How to find enthalpy and entropy change for chemical reactions
change in products - change in reactants
Free energy
state function that combines enthalpy and entropy
Gibbs free energy
usable energy, energy available to do work, Change in Gibbs energy = Change in enthalpy - Temperature (Change in entropy) (entropy of SYSTEM)
Exergonic reactions
negative free energy, lose usable energy as the process moves forward, spontaneous in forward direction, nonspontaneous in the reverse
Endergonic reactions
positive free energy, gain usable energy, nonspontaneous in the forward, spontaneous in the reerse
If gibbs free energy = 0
reaction is in equilibrium and no net change will occur
If Change in H is negative and Change in S is positive
reactions are spontaneous at all temperatures
If Change in H is negative and Change in S is negative
reactions are spontaneous at low temperatures
If Change in H is positive and Change in S is positive
reactions become spontaneous at high temperatures
If Change in H is positive and Change in S is negative
reactions are non-spontaneous at all temperatures
Solute
substance that experiences a phase change after dissolved
Solvent
the media that remains in that same phase after a solution is formed, solute is dissolved in this
Molarity and temperature
temperature dependent
The sum of mole fractions
always equals 1
Mole fraction and temperature
temperature independent
Mole fraction
Number of moles of A / number of moles of A + B
Molality
m, moles of solute / kg of solvent
Molality and temperature
temperature independent
Mass percent
Mass of component / total mass of components x 100
Mass percent and temperature
temperature independent
Parts per million
mass of solute / mass of solution x 10^6
Parts per billion
mass of solute / mass of solution x 10^9
Parts per million simplified equation
mg solute / kg solution
Parts per billion simplified equation
ug solute / kg solution
Unsaturated solution
solute’s concentration is lower than its solubility
Saturated solution
solute’s concentration is equal to its solubility
Supersaturated solution
solute’s concentration is greater than is solubility
Miscibility
ability of one liquid to dissolve in another liquid
Miscible
liquids successfully mix
Immiscible
liquids. do not mix
Two liquids are miscible phrase
like dissolves like
For a solution to form spontaneously
there is an exothermic change in the system (decrease in internal energy), increase in entropy (increase in disorder)
An increase in entropy ALWAYS occurs when
a solution has been made
Solutions being combined
is more energetically favorable that liquids on their own
Solute molecules need to
separate and spread out from other solute molecules
Solute molecules separating is a __ process
endothermic
Solvent molecules need to
separate and spread out from other solvent molecules
Solvent molecules separating is a __ process
endothermic
Solute molecules interacting directly with solvent molecules is a __ process
exothermic
Direction formation of a solution is a __ process
exothermic
If more energy was required to break bonds in solute and solvent than energy released in solution formation
overall heat of solution is endothermic
If the heat of solution is positive (endothermic)
adding heat will increase solubility of the solute
If more energy was released in the solution formation than energy required to break the bonds in the solute and solvent
overall heat of solution is exothermic
If the heat of solution is negative (exothermic)
adding heat will decrease solubility of the solute
As atomic radius of an ion decreases
the heat of hydration is more exothermic
As atomic radius of an ion increases
the heat of hydration is more endothermic
As the charge of two ions of similar size increases
(same period), the heat of hydration is more exothermic
As hydration processes become more exothermic
the process is becoming more spontaneous
Henry’s law
solubility of a gas in a solution is directly proportional to the partial pressure of the gas
As pressure increases, solubility of gas
will also increase
As volume increases, solubility of gas
decreases
As temperature increases, solubility of gas
decreases
Van’t Hoff Factor
moles of particles in solution / moles of solute dissolved
Experimentally determined VHF will always be
lower than the ideal
Percent ionization formula
= (experimental VHF -1) / (ideal VHF -1) x 100
Colligative properties depend on
the number of particles of solute and solvent and not the identity of the solute
Adding solute to a liquid has the effect of
lowering the vapor pressure
Raoult’s law
how the vapor pressure of liquid changes as a solute is added to the liquid
Raoult’s law formula
Vapor pressure of solution = mole fraction of solvent x vapor pressure of pure solvent
If we create a liquid-liquid system where both components are volatile
Ptotal = X solv 1 x Vapor pressure solv 1 + X solv 2 x Vapor pressure solv 2
Boiling point elevaiton
solute dissolved in liquid, solute lowers vapor pressure of liquid and boiling point increases
Boiling point elevation equation
Change in Tb = Kb(m)(I)
Freezing point depression
solute dissolved in liquid, solute interrupts ability of liquid to interact which decreases freezing point
Freezing point increases when molality
decreases
When solute increases, vapor pressure and boiling point
vapor pressure decreases, boiling point increases
Osmotic pressure
amount of pressure required to prevent the flow of a pure solvent into a solution through semi-permeable membrane
Osmotic pressure equation (pi)
pi = nRT / V (I)
R gas constant for osmotic pressure
R = 0.0821 L x atm / mol
Osmosis
movement of water from low concentration of solute to high
In osmosis solute cannot
move across semi-permeable membrane
Entropy increases with __ IMF
decreasing
Microstates increase with __ temperature
increasing
Temperature increases with __ entropy
increasing
Forming bonds
releases energy
Formation of solution steps
break solute-solute (exo), break solvent-solvent (exo), form solute-solvent (endo)
Favor spontaneous reactions
decrease in internal energy, increase in disorder
Ion-dipole attraction
electrostatic, between ion and molecule with a dipole, H2O molecules surround and solvate the separated ions, physical process, dissociation
If ion-dipole attraction dominate
compound it pulled in solution is highly soluble
If force of attraction between oppositely charged ions is dominate
component is undissolved in solid state, low water solubility
Solubility
rate is dissolution is equal to rate of precipitation
Supersaturated
concentration is greater than solubility
Unsaturated
concentration is lower than solubility
Exothermic temperature decreases and solubility
increases
Endothermic temperature increases and solubility
increases
Ionic and covalent solids
can dissolve
Solid dissolving in a liquid
endothermic
Solubility of solids __ with increasing temperature
increases
Increasing heat favors
formation of products
Miscible
two liquids that mix in all properties (ethanol, water)
Immiscible
two liquids that do not mix to an extent, NP liquids, gases, hydrocarbonds, water
Partially miscible
two liquids that are moderately soluble, bromine, water
Dissolution of gas in liquid
exothermic
Gas solubility decreases
temperature increases
Gas solubility and partial pressure
directly proportional
Making supersaturated solutions
high temperature, slowly cool, solid wont precipitate, at low temp solute concentration is greater than compound solubility
Molality
moles solute / kg solvent
More solute = ___ vapor pressure
decreasing
Solution boils at higher or lower temperature than pure solvent
higher
Boiling point elevation and freezing point depression are direct results of
vapor pressure lowering
Saturated solutions are
at equilibrium
Water evaporated unsaturated solution, vapor pressure above solution
decreases
Water evaporated saturated solution, vapor pressure above solution
equal
Intensive properties
units of concentration do not depend on size or amount
