What do we know about molecules in the same phase?
1) They are in the same state (liquid, solid, gas)
2) They have the same chemical composition (i.e. molecular formula is the same)
3) They are structurally homogenous (they have the same molecular structure...not isomers)
In its solid form, Sulfur forms S8 and S6 rings, among others. Are these in the same phase?
No...although they are both in the same state (both are solid) and they both have the same empirical formula (S or S2) they do NOT have the same molecular structure
Do different phases of the same substance have the same specific heat capacity?
No...1 substance in its solid or liquid state will have a much lower specific heat than the same substance in its gas state bc in its gas state a lot of the heat put into the system does work rather than increasing the temperature of the substance
When you see melting point/freezing point, what 4 things should you immediately think?
1) In general
2) Ex- Higher melting point
1) General:
-does it take more/less heat/energy to melt it
-does it melt at a higher or lower temperature
-if the temperature of the solution is in between its melting the point and the melting point of what you're comparing it to, which will be a solid a
When you see boiling point/condensation point, what 5 things should you immediately think?
1) In general
2) Ex.- Lower boiling point
1) General:
-does it take more/less heat/energy to boil it?
-does it boil at a higher/lower temp.?
-does it have a higher/lower vapor pressure at the same temp.?
-if the temp. of the solution is btwn its boiling pt. and the boiling pt. of the thing you're
?H of fusion...how does the temperature change at this point?
-For solid -> liquid ?H is positive bc it indicates the amnt. of energy needed to be put IN to increase convert from solid state to liquid state
-For liquid -> solid ?H is negative bc it represents the amnt. of energy that is removed when the substance co
?H of vaporization...how does temp. change at this point?
-For gas-> liquid ?H is negative bc it represents the amnt. of energy removed when it converted from gas to liquid
-For liquid -> gas ?H is positive bc it represents the amnt. of energy needed to be added in order to convert from liquid to gas
-Temp. does
How does the temp. of the air just above a liquid compare to the temp. of the liquid while the liquid is boiling?
-the temperature of both will be equal bc the liquid is currently undergoing a phase change and thus all the heat being added into the system is being used to break intermolecular interactions and is not being used to increase the velocity of the individu
Why do things boil? What things would you expect to increase boiling point?
-vapor pressure is a measure of how much pressure the molecules at the surface of a liquid are exerting on the atmosphere...it represents how much the liquid molecules want to leave the liquid and get into the gas phase
-as you increase the temp., you inc
What are the following phase changes called?
A) Solid -> Liquid
B) Gas -> Liquid
C) Solid -> Gas
D) Liquid -> Gas
E) Gas -> Solid
F) Liquid -> Solid
A) Melting
B) Evaporation
C) Sublimation
D) Boiling
E) Deposition
F) Freezing
What does volatile mean? Non-volatile?
Volatile means that a substance's vapor pressure exceeds atmospheric pressure at normal temperatures...thus, at very low temperatures, the substance boils...non-volatile is the opposite
Formula for the effects on boiling point from adding a non-volatile solute
?T = (kb)(m)(i) ...kb = boiling point constant of the solvent (units = Kelvin/molal)...m = molality (mol solute/mass of solvent in kg)...i = # of things present when it dissolves in solution (e.g.- glucose would be i = 1...Pb(NO3-)2 would be i = 3)
Why is the boiling point elevated when you add non-volatile solute?
-when you add a non-volatile solute to a solution, some of it is dissolved in the liquid deep down but some of it is dissolved and hangs out at the surface...remember that things boil bc their vapor pressure exceeds atmospheric pressure...you can imagine
Molality
m = (mol of solute)/(mass of solvent)...be careful to notice that the denominator is mass of SOLVENT only...not the entire solution
Formula for the effects on freezing point from adding a non-volatile solution
?T = (kf)(m)(i)...kf = freezing point constant of the solvent (units = Kelvin/molal)...m = molality (mol solute/mass of solvent)...i = # of things present when it dissolves in solution (e.g.- glucose would be i = 1...Pb(NO3-)2 would be i = 3)
Why is the freezing point depressed when you add non-volatile solute?
if you add a non-volatile solution to any liquid it will lower the freezing point (meaning that it will require MORE energy to be removed from the system in order to freeze it...this is the same thing as saying it has a lower melting point meaning that it
What determines the phase (solid, liquid, gas)? What determines the temperature?
-phase is determined by the degree of organization...at solid phase, the degree of organization is the highest...at liquid phase, the degree of organization is slightly less (fewer intermolecular interactions occur, and particles have more freedom to move
Osmotic pressure (?)
-a measure of the tendency of water to move from a high water concentration to a low water concentration (usually across a semi-permeable membrane)
-the side that will receive the water has the HIGHER osmotic pressure...thus, the lower concentration of wa
A cell is put into a hypertonic solution. Which side of the cell has the higher osmotic pressure.
The extracellular side has the higher osmotic pressure bc the extracellular side has the higher solute concentration (lower water concentration)...thus, water will flow out of the cell
Formulas for ?
? = iMRT...i = # of particles once dissolved...M = molarity...R = gas constant (.0821 L
atm/(K
*mol)...T = absolute temp. (kelvin)
? = (pgh1) - (pgh2)
How do you calculate ?H from a heating curve?
?H of vaporization = the heat added to change from liquid to gas...just measure the portion of the x-axis for the flat line btwn the liquid and gas phases
?H of fusion = the heat added to change from solid to liquid...measure the portion of the x-axis for
Draw a phase diagram
-Solid is the upper left portion...then liquid, then gas
-Pressure is on the y-axis...and temp. is on the x-axis
Under what conditions is sublimation possible? Under what conditions is deposition possible?
Sublimation happens when a solid converts DIRECTLY into gas...this happens at low temperature and low pressure...deposition ALSO happens at low temperature and low pressure; however, it happens by increasing the pressure or decreasing the temperature as o
What is the triple point?
This is the point at which the 3 phases intersect...to the left of this point on the graph is where sublimation and deposition can occur
What is the critical point?
It is the point on the graph at which critical pressure and critical temperature overlap...it is a point at the end of the line that separates the gas phase from the liquid phase...beyond this point (at higher temperatures and/or higher pressures) the sub
Supercritical fluid
-anything above the critical point
-has both properties of liquid and gas...it can dissolve substances in the same way liquids can...it can effuse through solids the same way that gases can
-the density of a supercritical fluid can be changed a ton by sma
Critical Temp.
-gases become more difficult to liquify above certain temperatures bc of the high kinetic energy of the particles
-above critical temp., no matter how much pressure is exerted, the gas can not be turned into NORMAL liquid...instead, it converts into a sem
Critical Pressure
-the minimum pressure required to liquify a gas at its critical point
-due to the high temperature of the gas, this liquification is actually just a conversion of the gas into its supercritical fluid state
What phases are (or are not) at the...
A) Triple point
B) Critical Point
A) Gas, liquid, solid...NOT supercritical fluid
B) Gas, liquid, supercritical fluid...NOT solid
Solution
-a homogenous mixture of two or more distinct compounds that are all in the same phase
-a mixture of various substances that are all in the liquid phase can be considered a solution...ALSO, a solution can be a mixture of various substances that are all in
Solvent, Solute, Solution
Solute is what you have less of...solvent is what you have more of...solution is the mixture of both (if they are both in the same phase)
Hydration
-something is dissolved in an aqueous solution due to water's intermolecular interactions with it...in order for something to dissolve in water, it must have greater intermolecular interactions with the water than it does with itself...or, as is the case
Hydration number
the number of molecules of water with which an ion can interact with in an aqueous solution of given concentration
Aqueous
-contains water
How would you expect the hydration number to change with...
A) Different concentrations of the ion
B) Different sized ions
...
Common Ion effect
You add compound AB to a solution and it dissolves into A and B...you then add compound BC to the solution and it dissolves into B and C. Bc you have added more B to the solution, this increases the ion product and causes the equation to run to the left a
Definition of a salt
a neutral compound made up of 2 or more IONS (permanently charged species)
Why do things dissolve?
-the intermolecular forces between the solute and the solvent determine whether or not something will dissolve
WATER examples:
-if the intermolecular forces are STRONGER btwn the solvent (water) and the solute (e.g. NaCl) than btwn water and water, then 1
What kinds of functional groups would a molecule need to be soluble in water?
1) ionic...ionic forces are stronger than H-bonds and thus ALL ionic compounds dissociate in water bc the water would rather interact with the extremely charged ions than H-bond with other water molecules
2) Alcohols (need abt. 1 -OH for every 5 carbons i
Why do micelles form?
-bc water molecules can not interact with hydrophobic molecules, the water molecules are forced to take up a super structured form which is energetically unfavorable due to the low entropy...thus, the hydrophobic portions turn in and form a micelle in ord
What is a colloid?
-colloids are NOT solutions
-colloids are solvents that contain undissolved solute particles that are too small to be separated by filtration, but are much larger than the dissolved solute particles in a true solution
-the undissolved solute particles ARE
What are some properties of colloids?
-colloids scatter light whereas solutions do NOT
-examples of colloids= paint; dust in the air; etc.
Molarity
(moles solute)/(liters of solution)
Molality
(moles solute)/(kg of solvent)
Why does molarity change with temperature but molality does not?
Molarity is a measure of moles/liter...thus, when temperature is increased, the volume will increase and this will decrease molarity...however, molality is a measure of moles/kg and the mass of an object does NOT change with temperature
Mole fraction
(moles solute)/(total moles solution) ...total moles of solution = moles of solute + moles of solvent
Mass percent
(mass of solute)/(mass of solution)*100
ppm...can you guess what ppb is?
(mass of solute)/(total mass solution)
10^6...ppb = same
10^9...parts per million does NOT mean how many solute particles there are per 1 million total particles...it is simply the mass percent *10^4...the purpose of multiplying by 1 million is to make ex
Normality
N = (# of equivalents)/(liters solution) ....# of equivalents = the # of hydrogen ions the solute would produce OR accept...ex- the number of equivalents HCl can produce is 1 and thus, molarity = normality for HCl...however, the number of equivalents that
What is required to create a solution?
-intermolecular interactions between the solute molecules must be broken
-intermolecular interactions btwn the solvent molecules must be broken
-finally, new intermolecular interactions are formed between the solute and solvent particles
What can you tell about the ability of something to dissolve based on the enthalpy value?
-?H = when the intermolecular forces btwn solute and solvent particles are GREATER (stronger/more stable) than the sum of the original intermolecular forces btwn particles of each of the pure liquids, then net energy is released and the process is deemed
What can you tell about the enthalpy based on whether something dissolves in a solution or not?
Nothing...unless you know the change in temperature of the solution as well...if the solution heats up, then you know that energy was released bc the new interactions formed between solute and solvent are more stable than the old interactions btwn solute
?Hsolution
Heat of solution (another form of enthalpy)
A certain mixture has a large negative heat of solution. Describe the relative strength of...
A) The intermolecular forces between solvent molecules
B) The intermolecular forces between solute molecules
C) The intermolecular forces between solute and solv
A) the forces are weaker than the forces btwn solute and solvent molecules
B) the forces are weaker than the forces btwn solute and solvent molecules
C) the forces are stronger than the forces of both the solute-solute molecules and solvent-solvent molecu
What happens to entropy when a solution forms?
Entropy always increases
Vapor Pressure
when the gas phase and liquid phase are in equilibrium with one another, the vapor pressure is equal to the partial pressure of the gaseous form above the liquid
How is vapor pressure affected by the following? And why?
A) Temperature
B) Addition of a non-volatile solute
C) Addition of a volatile solute
A) As temp. increases, vapor pressure increases...the average kinetic energy of the molecules in the liquid increases and this increase in energy allows the molecules to exert a greater pressure on the ambient pressure above them...this is why things will
What does solubility mean?
it refers to how many particles of the original compound are able to dissociate and dissolve in a solvent
Precipitate
the part that does not dissolve in a particular solvent...this may be because the substance is insoluble or because there is more solute available in the solvent than can be dissolved in the solvent and thus the extras precipitate out
Saturated solution
a solution that has the solute completely dissolved to the max...if any more solute is added to the solution it will precipitate out
Unsaturated solution
a solution that can still accomodate more solute...if more solute is added, it will still dissolve
Super-saturated solution
-solution that can accomodate MORE solute than it normally can according to the solute's NORMAL solubility...this may be a result of an increase in temperature
-solutes that don't dissolve all the way are essentially like endothermic reactions...the solut
Like dissolves like
polar substances are soluble in polar solvents and non-polar substances are soluble in non-polar solvents
Why are you able to leave out the pure solids and pure liquids from an equilibrium equation?
-you can only leave them out because the CONCENTRATION does not change...for example, pure water can be left out of an equilibrium equation bc in a particular reaction, the amount of water used up compared to the amount of water there is available is so s
What is Ksp?
Ksp = the equilibrium constant for how much of a particular solute dissolves in a solvent...it is the exact same as Keq, Ka, Kb, etc.
How to calculate Ksp
1) Leave out pure liquids and pure solids (thus, ALL your Ksp equations should be 1 line only!!! if you have a denominator, it's WRONG!)
2) Temperature is the ONLY thing that changes Ksp..or pressure, when dealing with solubility of a gas
3) Ksp can only
When can equilibrium constants be measured?
the ONLY times when equilibrium constants (Ksp, Keq, Ka, Kb, etc.) can be measured is when the reaction/solution is at equilibrium...at ANY other point in time, the measurement will be inaccurate
What happens to the Ksp in a supersaturated solution? How?
-Ksp increases...it increases because more is able to dissolve due to an increase in temperature
What is the difference between solubility and the solubility constant?
The solubility constant (Ksp) is a measure of how much of a substance dissolves into its various individual pieces in a solvent...the solubility is how many of the individual pieces can dissolve in the solvent...ex- CaCl2 -> Ca2+ + 2Cl- ...Ksp = [Ca2+][2C
Ion product
a.k.a. solubility product...ion product is to Ksp what Q is to Keq...if the ion (solubility) product is greater than Ksp then the reaction will go to the left and precipitate will form...and if the ion (solubility) product is less than Ksp, then the react
How to calculate solubility
1) Write out the Ksp expression
2) Substitute the value for Ksp into the expression
3) Substitute x into the equation for each ion (use 2x, 3x, etc. for each mole of an ion produced
4) solve for x...your answer, "x", is the solubility of that particular s
Describe the Common Ion Effect and define the term "spectator ion
-
What is the solubility for the following compound dissolved in water? CaCl2
Ksp = [Ca][Cl]^2 ... Ksp = [s][2s]^2 ... Ksp = 4s^3...what this question is asking is how much of the parent molecule was dissolved? thus, the parent molecule dissolved into 4s^3 solute particles, but there was still only "s" parent particles that actuall
What will happen if a common ion is added to a saturated solution? What will happen if a spectator ion is added to the same solution?
-if a common ion is added to a saturated solution, a precipitate will form...this is bc the common ion increases the # of dissolved ions in the solution and makes the ion product GREATER than the Ksp...thus, the rxn goes to the left and a precipitate form
What are some ways that you can drive a solubility reaction forward so that you can dissolve more of the original solid and form more of the dissolved products?
1) Increase temperature
2) Take away products (according to Le Chatelier's principle, more products will then be formed)...but how can you remove products that are soluble in a solution? you can remove them from the solution by several methods...Add acid
You want to dissolve more NaCl in an aqueous solvent (Ksp = 4.5
10^-5) so that you can harvest a solution with a lot more Na+ ions than you would get from simply dissolving NaCl in water. You can't use heat because you can't effectively store your solutio
Yes...you know that LiNO3 will be able to dissolve just fine in the solution without affecting its own ability to dissolve or the ability of NaCl to dissolve bc there are no common ions...however, LiCl is a precipitate that CAN form and it has a smaller K
Which components of a compound will immediately tip you off so that you can know that it is either soluble or insoluble on the MCAT?
Soluble: contains nitrate, ammonium, and ALL alkali metals (Group IA)
Insoluble: contains carbonate, phosphate, silver (Ag), mercury (Hg) and lead (Pb)...UNLESS one of these is paired with something from the soluble list; then it IS still soluble
5 General Characteristics of Gases
1) Gases are far less dense than liquids or solids
2) They contain much weaker intermolecular attractions than do liquids or solids
3) Gas molecules are very far apart
4) Gas molecules move very fast and collide billions of times per second
5) Gases are A
Why don't gas molecules eventually lose their energy as a result of constantly colliding with one another?
They must be perfectly elastic collisions in order for the energy to be conserved
Effect of temperature on gas solubility
Gas solubility is the exact opposite of solubility for liquids and solids...by increasing the temperature, the solubility of the gas DECREASES bc the vapor pressure will increase, and thus, more of the gas particles will leave the liquid and go into the g
Effect of pressure on gas solubility
By increasing the vapor pressure of gas X over a liquid, the solubility of gas X in that liquid INCREASES...(this is why they pressurize soda pop cans with excess CO2)
The Ideal Gas Law
PV = nRT ...R= ideal gas constant = 0.0821 L
atm/mol
K OR 8.31 J/mol*K
What assumptions are made concerning Ideal Gases?
1) Gas molecules have no volume
2) No intermolecular forces exist between gas molecules
3) All collisions are perfectly elastic
4) Average KE is exactly proportional to temperature
*Important! the first 2 assumptions the most responsible for the differenc
STP
Standard Temperature and Pressure...a set of standard conditions true of any ideal gas said to be "at STP"...for the MCAT assume that all gases are ideal and start out at STP
What are the values for each of the variables at STP?
P = 1 atm
V = 22.4 Liters
n = 1 mole
R = 0.0821 L
atm/mol
K or 8.31 J/mol*K
T = 273 K (0*C)
What is the difference between STP and Standard conditions?
Standard conditions usually indicates 25*C plus several other agreed-upon conditions at which thermodynamic data are always measured
What is the new volume of a gas that is increased to have 3 moles of gas and the new pressure on it is 2 atm?
Manipulate the equation! There is twice the pressure as normal which means that volume will be cut into half, but there are also 3 times as many moles which means that the volume is 3 times as great...thus, the volume ends up being 3/2 times as great
Another way to solve ideal gas problems
P1V1/T1 = P2V2/T2
In what situations would ideal gas behavior most differ from real gas behavior?
1) When the temperature is extremely low
2) the pressure is extremely high
-both of these situations cause the gas molecules to be very close together which allows for greater intermolecular interactions and several other things occur that cause a great d
How can you determine what caused a deviation from ideal gas behavior? (volume or intermolecular forces?)
1) If PV/RT > 1, then the cause is most likely due to the molecular volume assumption (gas molecules actually do have volume)
2) If PV/RT < 1, then the cause is most likely due to the intermolecular forces assumption (the gas does experience intermolecula
Formula for Dalton's Law of Partial Pressures
Ptotal = P1 + P2 + P3...
How will the following be affected if you add 1 mole of gas A to a mixture of gases A, B, and C?
1) Total pressure
2) Partial pressure of gas A
3) Partial pressure of gas B and gas C
4) # of moles of gas B and gas C
5) Mole fraction of gas B
6) Solubility
1) total pressure increases
2) Partial pressure of gas A increases
3) Partial pressure of gas B and gas C remain UNCHANGED
4) # of moles of B and C obviously doesn't change
5) Mole fraction of gas B decreases
6) Solubility increases bc total pressure incr
What is diffusion?
-the process by which gas molecules spread from areas of high concentration to areas of low concentration due to the random motion imparted to them as a result of their kinetic energy and collisions with other molecules
What is effusion?
the diffusion of gas particles through a pin hole
What is the definition of a pin hole?
a hole smaller than the average distance a gas molecule travels between collisions
Graham's Law
Rate1/Rate2 = ?(MW2)/?(MW1)...the rate can be the rate of either effusion or diffusion...notice that the rate of effusion or diffusion is INVERSELY proportional to the molecular weight of the gas
You have 2 different containers. In container A you have 8 moles of H2(g) and 2 moles of Cl2(g). In container B you have 2 moles of H2(g) and 8 moles of Cl2(g). Which container has higher pressure?
Neither...they both have the exact same pressure...according to the ideal gas law ALL gases behave the exact same way regardless of what gas it is
How can you change the boiling point of a particular species? What are some ways that might trick you into thinking it increases boiling point but really don't?
1) Increase/decrease ambient pressure...this makes it harder/easier for the species (that has the SAME vapor pressure) to break free of the liquid state
2) Add non-volatile/volatile solute (non-volatile solute crowd the surface and don't allow for as grea
If you change the boiling point of a substance, do you change its vapor pressure as well?
Not necessarily...when you add volatile/non-volatile substances you DO change vapor pressure...but when you simply change bp by increasing/decreasing ambient pressure, nothing happens to the vapor pressure
Also, when the boiling point changes, it only cha
What is the difference between evaporation and boiling?
1) Evaporation is a constantly occurring phenomenon...it is when particles of the solvent simply leave the liquid phase and enter the gas phase...this occurs at ALL temperatures but MORE particles do this at higher temperatures
2) Boiling is when you see
If the freezing point depression constant (Kfp = 1.86*C/m for water) what is the the freezing point of a mixture of 1.6 moles of glucose in 1000 g of H2O?
A) .003 *C
B) -.003*C
C) 3*C
D) -3*C
?T = Kfp(molality)(i) .... i for glucose = 1 ... molality = moles of solute/mass of solvent in kg = 1.6 molal ... 1.6(1.86)(1) = 3 ...but since the freezing point is being depressed, the ?T = -3*C...thus D is correct
Is ?H of fusion greater for a container of ice containing 10 gallons of ice compared to another container with only 1 gallon of ice? If you were to compare the energy diagram for the 2 different containers, which would have a longer horizontal line for th
1) No...?H of fusion = J/kg...thus, it doesn't matter how much of it you have...?H of fusion only measures how much energy is required to break apart the intermolecular interactions btwn molecules in a solid (or how much energy is released when the intera
If you have 500 mL of 1 molar H2SO4, what is the normality of the solution?
H2SO4 produces 2 mol of equivalents (H ions)...thus, normality = 2N
N = nM ...N = normality ...n = number of equivalents the solute produces in solution ...M = molarity of the solute
You have 100 grams of compound A (MW = 50g/mol) in a 200 mL solution. What is the normality of the compound. Assume that it is a diprotic acid.
2 moles of compound A in 200 mL of solution...thus, the molarity is 2/.2 = 10 M...we know that it is a diprotic acid, and therefore has 2 equivalents for every mole, thus we know that the normality is N = nM = 20 N
You have a 2 N solution of H3PO4. What is the molarity?
N = nM.... 2/3 = M = .66 M
You dissolve a solute in a particular solution and the solution and the beaker warm up. What does this tell you about...
A) ?H of solution
B) Solute-solute intermolecular forces
C) Solvent-solvent intermolecular forces
D) Solute-solvent intermolecular for
A) ?H is negative bc heat is released from the mixing into the environment
B, C, and D) The sum of the solute-solute and solvent-solvent intermolecular forces is WEAKER than the solute-solvent intermolecular forces
E) the new solution is more stable than
A particular solvent experiences highly attractive intermolecular forces with itself and is then put into a solvent. What will be required to make the solute dissolve?
Heat must be added...bc the solute-solute intermolecular forces are stronger than the solute-solvent intermolecular forces, this reaction is ENDOTHERMIC...heat must be added to get the solute to dissolve
1) Is a mixture of polar solute in water an exothermic or endothermic reaction?
2) Is a mixture of oil in water an exothermic or endothermic reaction?
1) Exothermic...the new intermolecular forces btwn solute and solvent are more stable...which is why it dissolves! a little bit of energy is released...could potentially warm up the beaker if -?H is large enough
2) Endothermic...the new intermolecular for
What is the solubility of CaCl2 in terms of S?
Ksp = [Ca2+][2Cl-]^2 ...replace the dissolved ions with S ... Ksp = [S][2S]^2 = 4S^3 ....if you were to use Ksp to solve for S, S would be equal to the number of particles of CaCl2 that would dissolve in solution
What is the vapor pressure of a boiling pot of water that is 1 meter tall? Calculate vapor pressure for the bubbles forming at the bottom of the pot.
Vapor pressure must exceed ambient pressure in order for the substance to leave the liquid state and enter the gas state...thus, we know that vapor pressure is at least equal to the pressure at the bottom of the pot....P at bottom of pot = 101.325 kPa + 1
What is the name for Ksp?
solubility product...equilibrium constant for solubility of a compound...if the ion product is greater than the solubility product, a precipitate will form
You are doing an experiment on 2 moles of gas molecules. However, your results are not matching the results you had expected when you calculated your estimates using PV = nRT. What is most likely causing the discrepancy?
PV/RT > 1...bc you have 2 moles of gas molecules...this means that your gas sample is not following ideal gas behavior which is why your results are off...specifically what is wrong, is that the gas molecules actually DO have volume and that assumption is
You are doing an experiment on a sample of a particular gas. You calculate the air pressure to be 2 atm in a 4 L space. The temperature of the gas is 25*C. However, you notice discrepancies in your expected data with the real data. What is most likely the
PV/RT < 1... 2(4)/(8.34)(298) < 1...this tells us that the gas is not following ideal gas behavior and the reason why is bc the assumption that the gas molecules are NOT experiencing any intermolecular interactions is the assumption that is violated bc PV
Osmolarity
Osmoles/L ... Osmolarity = Molarity*i ... i = number of things the solute dissolves into...NaCl = i = 2...glucose = i = 1
1) What happens to the temperature of water when you add salt?
2) What happens to ice when you add salt to it?
3) What happens to the melting point of water when you add salt?
1) DECREASES!!!
2) NOTHING
3) DECREASES!!
Explain the opposing forces of vapor pressure and partial pressure
-When vapor pressure = partial pressure, the system is at EQUILIBRIUM
-when vapor pressure > partial pressure, the liquid boils
-when vapor pressure < partial pressure, the liquid stays in liquid form
Rank the Ksp of the following molecules in order of smallest to largest:
1) Ammonia
2) Propane
3) 2-bromopropane
Ammonia > 2-bromopropane > propane
1) How does pressure affect Ksp?
2) How does temperature affect Ksp?
1) Pressure ONLY affects the Ksp of GASES...if pressure increases, the Ksp of the gas will increase
2) Temperature affects Ksp of solutes that are GASES, LIQUIDS, OR SOLIDS....if the solute is a liquid or SOLID, increasing temperature will INCREASE Ksp...
When do you use .0821 for R and when do you use 8.314 for R? What are the units of each?
1) .0821 J/mol*K ... J = Fd = PV = (F/A)(V)...you use this when you pressure is in Pascals (bc pascals are N/m^2) and when your volume is in m^3
2) 8.314 atm
L/mol
K... obviously you use this when your pressure is in atmospheres and your volume is in lite
If you add 50 grams of KNO3 (MM = 101 g) to 1 liter of solution, what is the molarity of the solution? The density of KNO3 is 2 g/mL.
calculate moles of KNO3 = .5 moles...you calculate the number of moles of the compound ADDED, without considering what dissolves in the solution....moles/liters of solution...you can ignore the change in total solution volume caused by adding the KNO3...?
You have a 2.3 M solution of Mg(NO3)2. If you were to have 2 liters of this solution, how many NO3 particles would you have in the solution?
The MOLARITY of the solution is what remains constant, NOT the number of moles of solute...2.3 mol/L, thus with 2 liters you have 4.6 moles of solute...4.6 moles of solute dissolves to give you 4.6 moles of Mg and 9.2 moles of NO3...(9.2 * 6e^23) = 5.4e^2
Calculating change in vapor pressure after adding a volatile solute
Raoult's Law = (mole fraction of the solvent)
(VP of the solvent) + (mole fraction of solute)
(VP of solute)
Calculating change in vapor pressure after adding a non-volatile solute
Raoult's Law = (mole fraction of the pure solvent)*(VP of the pure solvent)...mole fraction decreases when you add more solute
Henry's Law
Vapor pressure of solute = (mole fraction of solute)*(Henry's Law Constant)
What is the relationship between heat of solution and vapor pressure?
???