chem 102- exam #1
What are examples of a spontaneous processes? Hint: Think in terms of "these processes can only occur without added influence."
1. Solvation of a Soluble Salt 2. Expansion of a gas and diffusion 3. Phase Changes (Ice melting spontaneously, water evaporating) 4. Chemical Reactions (Iron rusts when exposed to the atmosphere)
ΔSsurr = quantity of heat (J)/ temperature (K)
For an exothermic process, ΔSsurr equation?
Polar molecules; non-polar
All alcohols are _______ ______(ethanol, C2H5OH, propanol, etc.). all Organics all ____-______. (c+h) Alcohols do not mix with organics. Alcohol makes polar & amines make it polar.
It also increases.
As the number of micro states over which energy can be distributed in a system increases, what happens to the entropy?
These values are close in number when water is the solution at a low concentration.
At a low concentration, what is the similarity in molarity and molality values?
With colloids, enough remain floating within solution therefore the colloid will never separate out. ion pairing means that a small percentage of ions are paired together and count as one particle instead of two.
Be able to differentiate between colloid & ion pairing
CH. 10
CH. 10
CH. 16
CH. 16
1. Change in BP- Elevation 2. change in FP -depression 3. Change in VP- Lowering 4.Ostmotic Pressure
Colligative Properties depend on # of ions: 1. 2. 3. 4.
Water will both enter and exit the bag; more water will exit the bag than entering it, therefore the bag will decrease in pressure.
Describe the "bag example" and whether or not the bag will increase or decrease in pressure?
ΔH1- Separate Solute particles ΔH2- Separate Solvent particles ΔH3- Solute-solvent interactions (EXOTHERMIC)
Describe the formation of a liquid solution using ΔH1, ΔH2, ΔH3. This results in ΔHsolvation. Which of these steps is exothermic?
Osmosis
Flow of solvent into the solution through a semipermeable membrane -Solvent can move through the membrane (higher concentration to lower concentration) and the solute cannot move through the membrane - Net movement of the solvent is always toward the solution with the higher solute concentration
ΔSsurr = - quantity of heat (J)/ temperature (K)
For an endothermic process, ΔSsurr equation?
T= ΔH/ΔS
How do we calculate the temperature where the reaction switches from spontaneous to not spontaneous or vice versa? (Hint: This is when ΔG =0)
ΔSsurroundings= -ΔHrxn/T
How do you calculate ΔSsurroundings?
liquids & solids are not affected by pressure, but the higher pressure of gas will result in increased solubility in gases
How does pressure impact solubility for liquids, solids, and gases?
Immiscible
If two liquids do not mix to form a solution, they exist in contact with each other as separate layers. Example: H2O and Octane
Miscible
If two liquids mix to an appreciable extent to form a solution, they are said to be ________ Example: H2O and Ethlylene Glycol
Spontaneous at high temperatures
If, then: ΔH is + ΔS is + ΔG is ?
Never Spontaneous; always reactant favored
If, then: ΔH is + ΔS is - ΔG is +
Always spontaneous
If, then: ΔH is - ΔS is + ΔG is -
Spontaneous at low temperatures
If, then: ΔH is - ΔS is - Δ G is ?
Second Law of Thermodynamics
In a spontaneous process there is always an increase in the entropy of the universe. The entropy of the universe is increasing; therefore, energy and matter tend to become more disordered.
Parts Per Million (PPM)
In very dilute solutions, this measurement is common. It is calculated by mass of A/ total mass x 10^6
Parts Per Billion (PPB)
In very dilute solutions, this measurement is common. It is calculated by mass of A/ total mass x 10^9
ΔSuniverse is positive when spontaneous.
Is ΔSuniverse positive or negative when the reaction is spontaneous?
Polar solutes; non-polar solutes; like dissolves like
Polar solvent dissolves ______ solutes, non-polar solvents dissolve ___________ solutes. AKA: "_____ dissolves _____"
Exothermic
Spontaneous reactions are often ________, but many spontaneous reactions have ΔH > or equal to 0.
Standard Molar Entropy (Snot) is the entropy gained by converting 1 mol of it from a perfect crystal at 0 K to standard state conditions at the specified temperature.
Standard Molar Entropy
Colloid
Suspension of tiny particles in some medium
Third Law of Thermodynamics
The entropy of a perfect crystal approaches 0 as the temperature approaches 0 K. No disorder in a perfect crystal at 0 K. -Defined by Ludwig Boltzmann, states that a perfect crystal at 0K has zero entropy; that is S=0.
First Law of Thermodynamics
The law of conservation of energy; energy cannot be created or destroyed. The total energy of the universe is constant.
van't hoff factor, i
The relationship between the moles of solute dissolved and the moles of particles in solution is usually expressed as: i= moles of particles in solution/moles of solute
Tyndall effect
The scattering of light by particles (shining light through a colloid)
Spontaneity
The tendency to occur without being driven by an external influence while giving no information about the speed of the process -- "Naturally Occurring Change" Examples of a ____ change: - Ice being placed on the table and melting results in melting, which is _____. - When your hand is on a hot cup of coffee, the heat transfers from the hot coffee to your hand ________.
Psolution= Solvent x Ppure solvent
What is Raoult's Law?
Microstates
These are one particular arrangement or state. The more micro states, the increase in entropy. As gas expands into a vacuum to give a uniform distribution since the expanded state has the highest positional probability of states available to the system. Ssolid < Sliquid << Sgas
Ionic Solids
These are soluble in polar water and insoluble in non polar solvents.
ΔG
This also s the maximum possible useful work obtainable from a process at constant temperature and pressure is equal to the change in free energy. -Achieving the maximum work available from a spontaneous process can occur only via a hypothetical pathway because all processes are irreversible. Example: ΔG is -100 kJ, then 100 kj of work can be done. If ΔG is 100 kJ, then no work can be done because the reaction is not spontaneous.
Solution
This is a homogenous mixture of two or more substances in a single phase. - The component in the largest amount is the solvent and the component in the small amount is the solute.
Miscible
This is a homogenous mixture that is easily distributed.
Entropy
This is a measure of disorder. The more disordered, the increase in spontaneity. When a substance dissolves, the process is spontaneous owing to the INCREASE IN ENTROPY. Matter and energy are more dispersed. The number of micro states is increased. - This is known as the driving force of spontaneous processes. - Describes the number of arrangements that are available to a system existing in a given state Properties of _____: -Measures disorder -State Function of ΔS= products - reactants - This increases with increasing temperature, due to temperature increasing the number of microstate energy positions.
Molarity
This is a measurement of moles of solute per liters of solution. This is represented by M.
Molality
This is a measurement of the moles of solute per kilograms of solvent.
Immiscible
This is a non-homogenous mixture.
Mass Percent-Weight Percent
This is calculated by taking the mass of A/total mass x 100%
ΔH
This is heat transferred at a constant pressure. If ΔH is negative, then the reaction is exothermic bc heat is leaving the system. If ΔH is positive, heat is coming into the system and is endothermic.
Nonpolar Paraffin
This is insoluble in polar water. It is soluble in non polar CCl4. (used to seal pipes)
Polar Sugar
This is soluble in polar water. It is insoluble in non polar gasoline.
Gibbs's Free Energy
This is the available energy to do work. This is the method used so far to determine whether a process is spontaneous required evaluation of two quantities (ΔSsystem & ΔSsurroundings) - The maximum non-PV work available to the system must be a function of enthalpy and entropy. -All the useful energy a substance contains. At equilibrium, ΔG=0 --> at equilibrium with a phase change, and when a non-spontaneous reaction becomes a spontaneous reaction
1. solid -> Liquid -> Gas 2. Small Moles -> Large Moles 3. Increase in Temperature 4. Small molecules -> Large molecules 5. Increase in Volume 6. Increase in Pressure 7. Pure -> Impure 8. Small to Big Things ---ΔSsystem
What are the 8 rules that result in the increase in entropy? What do these directly correlate to the calculation of?
ΔG= ΔH-TΔS This allows us to see if a reaction is spontaneous or not, due to it's relation to ΔSuniverse.
What equation is associated with Gibbs Free Energy?
ΔSuniverse = ΔSsystem + ΔSsurroundings
What equation is associated with the second law of thermodynamics?
Based on osmosis, the solute does not actually move to maintain the gradient, rather the solvent moves to level out the number of solute molecules and adjust the gradient. The solvent flows from low to high.
What gradient does the liquid solute flow?
low concentration to high concentration
What gradient does the liquid solvent flow?
C=Kh x Pi The amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the solution. This depends heavily on temperature.
What is Henry's Law?
-ΔG (Product Favored, spontaneous, reaction will occur)
What is the value of ΔG if the reaction is spontaneous? What is another way to term spontaneity concerning a reaction?
ΔG, ΔSuniverse; they are always the opposite signs of each other
What two things tell us if a process is spontaneous? How are they related?
The wide range is based on ion dipole. Sometimes there are ions that are so attracted to each other that they are harder to break off.
Why is there a wide range in solubility in water?
Mole Fractions
Xa=moles of A/total moles
Exothermic
_________: ΔH < 0
Endothermic
_________: ΔH > 0
ion pairing
this is at a given instant a small percentage of the sodium and chloride ions are paired and thus count as a single particle. Ion pairing is most important in concentrated solutions. As the solution becomes more dilute, the ions are farther apart and less ion pairing occurs. Ion pairing occurs to some extent in all electrolyte solutions. This is most important for highly charged ions.
density
used to convert mass to volume or volume to mas
Spontaneous at lower temperatures ΔG is product favored at low temps.
ΔH < 0 ΔS < 0 Spontaneous process? Related to ΔG?
Spontaneous at all temperatures Negative ΔG, due to it being spontaneous
ΔH < 0 ΔS > 0 Spontaneous process? Resulting in what value of ΔG?
Not spontaneous at any temperature ΔG is not spontaneous at any temperature.
ΔH > 0 ΔS < 0 Spontaneous process? Related to ΔG?
Spontaneous at higher temperatures ΔG is product favored at high temperatures
ΔH > 0 ΔS > 0 Spontaneous process? Related to ΔG?
