Chp 5 Flashcards
if apply pressure above, ex
if apply pressure above, ex carbinatd drink in a can, if you keep it closed like pressure over it it doesn’t go flat as much, you are pushingn down the gas so it stays in solution!!!
so another good way to get soda or beer to go flat leave for a while, low CO2 allows all the pressure to come out of solution
solubility
supersaturated
tricked system to hold more solute than it normally would at a temperature
ex. sugar water solution, at higher temp sugar more soluble get more in
then cool it down really really slwoly do not docile table, adn sometimes if really careful can get solution to still be holding more solute than it normally would at lower temp, very unstable as a system but can have a scenario where you get the solution to add extra solute for a while- super saturated solution* but if sneeze or drop in a seed cyrstal you would get percipitaiton
molalilty***
little m
= # moles of solute/kg of solvent
now dealing with MASS units and just solvent
DOES NOT CHANGE WITH TEMPERATURE
this can be important, vol of liquid doesnt change that much when change temperature but can change a bit
molarity can vary slightly when change temperature, but here mass units of kg in denominator no change when you change the temperature**
Molarity
moles of solute/ L of solution
L = volume units
solution= whole solution
telling you how much stuff is dissolved, how many moles of stuff disolved either per unit of solution or per unit of solvent** usually really similar
mole fraction X
X= #moles of A/ total # of moles
mass percent
ex
mass of A / total mass
ex. if a solution is 3% glycerol by mass= assume 100grams, so assume 100 grams and then you can say you have 3 grams of glycerol and 97 grams of water*** so sometimes then if trying to do MOLALITY needed to know mass of solvent this is how you think about it, if 3% glycerol by mass then say ok 3 grams of glyceorl but 97 grams of water; if doing molarity 100 grams of the whole solution*
how ot unpack mass percent to give you other numbers can use for other concentraiton units
density of water
1 g/ mL
assume on mcat aqueous solutions, density same as water
Colligative properties
definition=properties depend on the NUMBER of particles in a solution, the concentration not hte kind of molecule it is**
ex. if have 1 molality solution of salt water it depends on how many particles you have in the solution, the identity of the particles does not matter, so properties that work that way are called colligative properties
ex. vapor pressure, bp, freezing point comparing what happens in solution to scenario with original pure solvent
Boiling point
change in bp, more concentrated more solute in there bigger change in boiling point and then number of parts
change in BP= kb (constant) X m (molality) X i (# of parts of solute breaks into in solution, number of ions)
kb= 0.51 for H2O
ex. glucose, i= 1
for NaCl, i= 2
MgCl2, i=3
then add this delta BP to old boiling point to get new boiling point
osmotic pressure
higher molarity, more salty a solution is more solute is dissolved the higher the osmotic pressure will be
greater M gives you bigger osmotic pressure
connected this with bio- if a capilary has very high osmotic pressure, means very high solute concentration and means water really wants to come rushing in** so more concentrated the saltier the blood is the higher hte osmotic pressure becaue water will want to flow in, one of the ways blood pressure can go up, more solute means more water means more volume means higher blood pressure
normality
N= M X n
concentration X number of hydrogens
if HCL- one H, so n= 1
ex. 0.15 M HCl 0.15 X 1
= 0.15 normality*
normality ex.
H2SO4
NaOH
ex. 1.4M H2SO4–>
N= 1.4 X 2= 2.8 N
ex. 2 M NaOH (ONLY 1 H so n=1)
so normality = 2x1= 2N
ex. 0.4 M BaOH 2
0. 4 X2= 0.8 N
another eq for normality
equivalent weights/L
(liters of solution)
number of equivalent weights , 1 ew= mass that yields 1 mol of protons/H+ for acids
for bases 1 mol of OH ions**
step 1. start with 1 mol of H+ and convert it to the grams of substance this will give you the number of equivalent weights*, one equilvanet weights is the mass of 1 mol of H+ take grams of substance and convert it to the nomality( eq w/L)
what is the normality of a solution that contains 50 g of H2SO4 dissolved in 15 L?
what is the normality of a solution that contains 1.5 g of Ca(OH)2 dissolved in 850 mL?
- which of the following is a true statement?
a. a saturated solution is concentrated
b. an unsaturated solution is dilute
c. a saturated solution can be dilute
d an unstruated solution can be at equilbirum
unsaturated solution can have more solute added/dissolved, terms concentrated and dilute mean that not a lot of solute has been dissolved in the solvent, and concentrated means a lot of sovlent has been dissovled in the solvent, but those two pairs of terms are relly really different from each other, can have a solution very very concentrated from each other, but solution is still not saturated* becuase its a capacity of that solvent to take a lot fo sovlent is high terms are just indpednet of each other, a saturated solution can be dilute OR it can be concnetrated
saturated just means solution is maxed out, a lot of solute present or not a lot of solute prsent*
a is too strong a statement, c is correct a staurted solution can be dilute
d. its a definitional things, equilbirum is the SATURATED SOLUTION** when get to saturated solution that means you are AT equilbirum
lattice energy
tells you how hard it is to rip apart the ions in a crystal lattice, crystal lattice are structures find ions ins Na+ with Cl- Cl-
in three dimensions, questions i who amuch would it take to rip apart the crystal lattice of the ionic solid*
harder to pull ions apart* same as saying higher absolute value of lattice energy if greater charge on ions or smaller radius of ions*
if greater charge on ion more force there will be between them they will really stick to each other, the smaller the radius of the ions the more tehy are really able to stick to each other, so the reason teh answer to number 12 is A is becasue F is so small KF would have hte highest lattice energy** b/c its radius is so small*
- lattice energy corresponds to the energy change when gaseous ions come together to form an ionic solid. The absolute value of the lattice energy is hgiher when bond stregnth is greater. The absolute value of lattice energy should be highest for:
a. KF
b. KCl
c. KBr
d. KI
if greater charge on ion more force there will be between them they will really stick to each other, the smaller the radius of the ions the more tehy are really able to stick to each other, so the reason teh answer to number 12 is A is becasue F is so small KF would have hte highest lattice energy** b/c its radius is so small*
answer a
- The absolute value of lattice energy should be highest for:
a. NaOH
b. Mg(OH)2
C. AL (OH)3
d. Ca(OH)2
c. Al (OH)3
one that has the highest charge on one of the ions, will be hte hardest crystal lattice to rip apart becuase highest charge makes for very strong interactions between the ions*
if you have Na OH, for all of them OH will be OH- and Na will be Na+, all causes OH-1 but here ion with +3 charge greatest charge for an ion of any of these examples that would have the highest lattice energy, how much energy it would take to pull apart AL from OH to get Al out of there compared to mg2+ or ca2+ because the charge allows for a very strong electrostatic interaction**
- A non-volatile solute will cause an increase in which of the following?
a. the vapor pressure of the solution compared to the pure liquid
b. the bp of the solution compared to the pure liquid
c. the freezing point of the solution compared to the pure liquid
d. the temperature of the solution compared to the pure liquid
nonvolatile solute think normal solute like salt in water, non-volatile means system would evaporate, system would behave differently think normal solute like salt in water or sugar
THINK ABOUT Colligative properties, idea bp is elevated is a correct statement about hte different colligative proprties** answer b
= boiling point of the solution compared to the pure liquid
