Chem 108: Exam 2
DTb = iKbm
lower vapor pressure means need higher temp to boil dTb=increase in boiling point, i=van't Hoff factor, Kb=proportionality constant, m=molality
Unit of measurement for osmolarity
osmol/L OR moles of individual dissolved species/L
Polarity of C-O bonds and O-H bonds
C-O bonds are NOT as polar as O-H bonds
Benzene Molal Points
C6H6 Freezing Point: 5.5C Kf: 4.9 C/m Boiling Point: 80.1C Kb: 2.53 C/m
Carbon Tetrachloride Molal Points
CCl4 Freezing Point: -22.3C Kf: 29.8 C/m Boiling Point: 76.8C Kb: 5.02 C/m
Ethanol Molal Points
CH3CH2OH Freezing Point: -114.6C Kf: 1.99 C/m Boiling Point: 78.4C Kb: 1.22 C/m
Magnitude of charge with van't Hoff Factor
More Charge means more IMF. So it is less likely to be overcome by water
More energy is needed to reach the boiling point for a solution compared to pure solvent
More energy is required to overcome IMF
Osmosis
Movement of solvent across a semi-permeable membrane
Will 2 sides of a U beaker ever reach equilibrium of solution
No because there is more gravity on the higher concentration solution. This is due to increased osmotic pressure
Collisions of elastic molecules
No loss of energy when collided. There are no attractive forces or space taken up
Stabile Substances
Non volatile substances. Not readily vaporized, high IMFs. More easily dissolved
Significant Figures 0's rule
Non-zero digits are always significant. Any zeros between two significant digits are significant. A final zero or trailing zeros in the decimal portion ONLY are significant (If no decimals, following zeros are not significant)
Gas Law
PV=nRT
After holding your breath for a long time and you inhale
Pressure increases greatly, and so will also increase the number of moles
If temperature is raised, what happens to the pressure in the system?
Pressure is increased because of direct relationship
If volume is increased, what will happen to the pressure in the system?
Pressure will decreased because indirectly related
Colligative Properties
Properties of solutions that depend ONLY on the NUMBER of solute particles present. Does NOT focus not the identity of solute particles
Kb, molal boiling point
Property of EACH solvent.
In the middle of the afternoon, is water over the water or the land less dense?
The air over the land
Which body of air will rise at the beach?
The air over the land because it's less dense than the air over the water
Significant Figures while Adding/Subtracting
The answer will have the same number of SMALLEST sig fig number (from the last order of operation)
Significant Figures while Multiplying/Dividing
The answer will have the same number of SMALLEST sig fig number (from the last order of operation)
Molecular Speed and Temperature
The colder the molecule, the less speed it has
What can we say about density of the gas in the shark ballon
The density of the gas inside the shark is lighter than the density of gas in the room
DTf = iKfm
solute particles interferes with formation of lattice arrangement of solvent molecules dTf=freezing point depression, i=van't Hoff factor, Kf=proportionality constant, m=molality
When using the osmotic pressure law: R Value
.0821 L/atm
van't Hoff Factor for molecular compounds
1
Liter/Grams Ratio
1 Liter/1000 grams
Atmosphere (atm)
1 atm
Pascal (pa)
1 atm= 1.01325 x 10^5 PA
Kilopascal (kPa)
1 atm= 101.325 kPa
Millimeter of mercury (mmHg)
1 atm= 760 mmHg
Bar
1 atm=1.01325 bar
Milibar (mbar)
1 atm=1013.25 mbar
Pounds per square inch (psi)
1 atm=14.7 psi
Inches of mercury
1 atm=29.92 inches of Hg
Torr
1 atm=760 torr
How to determine the van't Hoff factor of a solute?
1) check if it is an ion or molecular compound 2) Check its formula (ion parts)
Boiling Point Elevation
A colligative property. Solvent is most important, temperature-dependent, so temperature-independent concentration units are used.
Melting Point Depression
A colligative property. Solvent is most important, temperature-dependent, so temperature-independent concentration units are used.
Vapor Pressure Depression
A colligative property. Solvent is most important, temperature-dependent, so temperature-independent concentration units are used.
Osmotic Pressure
A colligative property. Molarity is used, but T appears in formula
How to make a non polar molecule more soluble?
Add an Acid or a Base
How to find the liters of solution when given grams and density of the solution
Add up the Grams of solution and set ration of 1ml/grams (density) and multiply it by 10^3 to go from mL to Liters
DTb or DTf
Added to the normal boiling or freezing point of the solution
Alcohol Functional Group Solubility
Alcohols can have H bonds, making them very polar
Pressure formula
Amount of force applied to an area: P=F/A
Similarities of Gas laws
Molarity formula is used to derive it
Ideal gas
At STP, 1 mol of ideal gas/22.414 L
What factors are affected if you heat a steel container?
Average kinetic energy per gas particle. Collision Frequency. Pressure
How to check to see if a solute is soluble
Consider the solvent, is that polar or non polar. Then look at the solute, what intra/intermolecular bonds does it have?
When using the osmotic pressure law: Temperature
Convert it to Kelvins
To determine what is the solvent/solute when given the grams of substances
DO NOT COMPARE WITH THE GIVEN GRAMS. Convert the grams to moles With the molecular weight
When inhaling air
Diaphragm contracts and is pushed down. Pressure decreases, volume increases
When exhaling air
Diaphragm relaxes and is pushed up. Pressure increases, volume decreases
Pressure units of a barometer
Difference in heights
Strong Electrolyte
Dissociates "Completely" to form ions in solution.
Osmosis regarding solutes
From lower concentration of solutes to a higher concentration of solutes
Which direction will air flow if you are standing at the shore
From water to land because pressure moves from higher to lower
Differences of Gas Laws
Gas law is "Gas" Based. And osmotic pressure is solution based
Kinetic-Molecular Theory
Gases consist of large molecules of molecules that are in a continuous, random motion.
Each mole of solutes (Electrolytes)
Gives more than 1 mol of dissolved particles
Water Molal points
H2O Freezing Point: 0.0C Kf: 1.86 C/m Boiling Point: 100C Kb: .52 C/m
Hypertonic Solution
Higher concentration of dissolved solutes. Example: Corn Syrup or Salt Water
Osmosis regarding solvents
Higher concentration of solvents to a lower concentration of solvents
Molarity Formula
Molarity= moles of solute/liters of solution
What affects the density of a gas?
Molecule's nucleus size. Even if you have the same number of molecules, what matters is it's weight
Pressure of a gas is measured by
Molecules colliding with the side of the container
In a closed system, relationship of volume and pressure
Increase in volume will lead to a decrease in pressure
Formula of a compound
Indicates the expected number of particles into solution
Solubility of polar head with long, non polar body (Like stearic acid)
Is not soluble in water or octane because of the polar/non polar ratio. it forms a Miscelles
As you go higher in elevation, what happens to the pressure?
It decreases. Molecules of gas are farther apart
In order for a solute to change the boiling point of a solvent
It has to dissolve
If you're at the bottom of a pool, what happens to the pressure
It increases because gravity/pressure is increased
What happens to a pendulum in an accelerating car
It will move towards the back of the car because it is more dense than the air
What happens to a helium ballon in an accelerating car
It will move towards the front of the car because it is less dense than air
Hypotonic Solution
Lower concentration of dissolved solutes. Example: Water
When solving a molality/molarity/ solution ratio
Make sure to Label all aspects of the equation with actual problem's units (to minimize confusion)
Osmolarity
Measure of solute concentration
Barometer
Measures atmospheric pressure in the air
Molality Formula
Molality= moles of solute/kg of solvent
Volatility of a Substance
Related to the substance's vapor pressure.
Isotonic solution
Same concentration of solutes and solvent in solution
How to find Mole Fraction of a solution
Set up ratios with labels, multiply by the molecular weight to get grams- moles. Last ratio: Solute (moles)/ Solute+ Solvent (moles)
The freezing point of water is lowered proportional to the number of solute species present
So the substance with a higher van'T Hoff factor will contribute more particles- the more the freezing and boiling points.
How would you confirm the results of the egg test were not a fluke?
Switch the eggs from their baths and TEST AGAIN!!
Why are some ionic compounds more soluble than others
Take into effect Coulomb's law. If an ion is more stable together, the less likely water will break those strong dipole-dipole interactions
van't Hoff Factor for electrolytes
Takes into account the dissociation of a strong electrolyte to credit the effect of the solution
What does the barometer depend on?
Temperature, location, weather.
What do you predict will happen when an egg is placed in hypotonic solution?
The Water will enter the egg/cell and the egg will INCREASE in mass
What do you predict will happen when an egg is placed in hypertonic solution?
The Water will leave the egg/cell and the egg will DECREASE in mass
When a solute is added
The freezing point is lowered and the boiling point is raised
The lower the vapor pressure
The less readily the substance will vaporize. The lower the volatility, t he substance can be readily found as a liquid or solid
The higher the vapor pressure of a substance
The more readily the substance will vaporize. The higher volatility, the substance can readily found as a gas
If you close your mouth and nose while you breathe in
The pressure in the lungs when you try to inhale will be less than atmospheric pressure
Actual driving force that makes breathing occur
Vacuum force because the pressure and volume gradient changes
Atmospheric Pressure
Weight of the air per unit of area
A dissolved solute in a solution which contains very polar bonds will have a bigger Impact on the change in boiling point than a less polar compound
Yes, it feeds back into the van't Hoff factor. The more polar a substance is, the more it will separate
Saline
You can't give a patient straight water into their veins, because the red blood cells will burst. You need the salt to balance out the water
Why could handling PCP without gloves be dangerous for your brain
Your fingers are hydrophilic and PCP is Non polar. The 2 substances could interact and sink into your blood stream.
When doing van't Hoff problems
Your guess is a POSSIBILITY. You really need a solubility chart and experimental values to be sure
pi=iMRT
sucking pressure generated by solutions in which water is drawn into a solution, amount of pressure that must be applied to counteract the attraction of water molecules for the solution pi=osmotic pressure, i=van't Hoff factor, M=molarity, R=ideal gas, T=temp water moves to higher solute concentration
Osmotic Pressure Gas Law
π=iMRT