Solutions Flashcards
1
Q
What is molarity?
A
mol of solute / L of solution (M)
2
Q
Molality
A
mol of solute/ kg of solvent (m)
3
Q
Molality is for what type of properties only?
A
colligative properties
4
Q
Colligative Properties
A
properties that depend only on the number of particles, not the identity
5
Q
What are the 4 colligative properties?
A
vapor pressure, boiling point elevation, freezing point depression, and osmotic pressure
6
Q
What is about the same in dilute solutions?
A
.1 M is about .1 m
7
Q
Mass percent
A
compares the grams of solute to grams of solution
8
Q
Mole Fraction
A
compares the moles of solute to moles of solution
9
Q
What 3 things occur when dissolving a substance?
A
- the solute expands (IMF are broken) - lattice energy
- the solvent expands (IMF are broken)
- the solute and solvent combine (new IMF are formed)
10
Q
Enthalpy of the solution
A
total of enthalpy changes when dissolving
11
Q
Enthalpy of hydration
A
changes when already separated solute is added to water
12
Q
Explain the dissolving process with a nonpolar solute and polar solvent
A
- non-polar solvent is delta H1: has small IMF (LD) + bonds being broken = small to medium positive enthalpy
- polar solvent is delta H2: has large IMF (H-bonds or dipoles) + bonds being broken = large positive enthalpy
- delta H3: has essentially zero IMF because they don’t mix= small positive enthalpy
- enthalpy of solution: small positive + larger positive + small positive = very larger positive
- No solution forms (immiscible = does not dissolve in any amount. - don’t mix
13
Q
Explain the dissolving process with a polar solute and non-polar solvent
A
- polar solute = delta H1 = large IMF + bonds breaking = large positive
- nonpolar solvent = delta H2 = small IMF (LD) + bonds breaking = small positive
- delta H3 = small positive (no IMF)
- enthalpy of solution= large positive + small positive + small positive = larger positive
- no solution forms (immiscible) - don’t mix
14
Q
What happens with the enthalpy of the solution is large and positive?
A
NO solution forms (immiscible)
15
Q
What happens when the enthalpy of the solution is negative?
A
the solution will form (miscible)
16
Q
Dissolving process for polar solute + polar solvent
A
- polar solute = large IMF + bonds breaking = large positive
- polar solvent = large IMF + bonds breaking = large positive
- energy is released when new IMF forms = very large negative
- enthalpy of the solution = probably negative - solution will form
17
Q
What happens when the enthalpy of the solution is small?
A
solution will form
18
Q
Polar solute & polar solvent (small enthalpy)
A
possible small positive enthalpy of solution- still miscible
19
Q
nonpolar solute & nonpolar solvent
A
- solute = small positive (IMF + broken bonds)
- small positive (IMF + bonds broken)
- delta H3 = small positive
- enthalpy of the solution is small & positive because the increase in entropy overcomes any positive enthalpy of the solution
20
Q
C-H bonds are
A
non-polar (because of similar electronegativites)
21
Q
-OH groups make H-bonds that are
A
polar (H-bonds - strongest)
22
Q
“ol” at the end of a structural formula means
A
alcohol
23
Q
C-O and C-N bonds are
A
polar (two dissimilar non-metals -two different electronegativities)
24
Q
-COOH group
A
- carboxyl group
2. polar
25
H at the end of -COOH ionizes to make
an acid
26
How can a large molecule with C-H bonds be considered polar
must have many polar groups (more elcectrons)
27
fats & oils = large C-H molecules are
nonpolar
28
What are the 2 types of vitamins
1. water-soluble (polar) must be replaced daily (C, B)
| 2. fat soluble (non-polar) are stored in the body (A, D, E, K)
29
halides
dissolve best in water (ionic or polar)
30
halogen
dissolve best in non-polar solvent like mineral oil ( LD )
31
What will a polar solvent & non-polar solvent form when mixed
two layers
32
What are the factors that affect solubility?
structural factors (polar vs. nonpolar), pressure effects, and temperature effects
33
pressure has little effect on
solids and liquids
34
What does pressure affect?
the gas dissolved in a liquid
35
What happens when more P is added?
1. increase in # of dissolving gas molecules
| 2. new equilibrium is established with MORE gas dissolved
36
Henry's law
amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the solution
37
When the temperature is increased what happens
1. the rate of solubility is increased
| 2. the volume of the solution increases slightly
38
What occurs when you decrease the temperature of the water?
1. it decreases the water's volume until 4 C - water is opposite this trend after 4 C; because the H-bonds are making the liquid become solid (water is larger as a solid
39
temperature cannot predict
the amount of solubility
40
solubility is dependent on
temperature, IMF, and # of e-s (not mass)
41
What is the effect of a non-volatile solute on the VP?
1. it lowers the VP because the molecules are blocking the water molecules
2. more molecules will leave than pure solvent the solution
3. all the pure solvent will evaporate as the solution continues to pull molecules from the air
42
Raoult's Law
the direct relationship between mole fraction of solvent and VP of solvent
43
a solution is considered ideal when
the solute and solvent do not interact ( the interaction between each are similar) - a solute is the dilution the solution
44
what occurs when the observed VP is lower than expected (non-ideal)
1. negative deviation from Raoult's law
2. fewer molecules are evaporating than expected
3. enthalpy of the solution is larger and negative (exothermic)
4. the solvent and solute must attract each other in H-bonds
45
what occurs when the observed VP is higher than expected (non-ideal)
1. positive deviation from Raoults law
2. more molecules are evaporating than expected
3. the solute and solvent must repel (polar and non-polar mix)
46
vapor pressure is affected by
temperature, # of electrons, and IMF
47
When something is dissolved in water, what happens to the vapor pressure?
the vapor pressure goes down because the dissolved particles get in the way so fewer water molecules are able to escape
48
boiling point occurs when
VP = atmospheric pressure
49
freezing point occurs when
VP (liquid) = VP (solid)
50
what happens to make the boiling point of water go up when something is dissolved in water?
the vapor pressure of water must equal 1 atm of 760 torr to boil and the VP of pure water is 20 torr at 20 C; therefore it takes longer for the temperature to continue to rise
51
why does the freezing point go down as more particles are added to a solution?
the solute interferes with crystal formation
52
osmotic pressure
the pressure needed to stop osmosis
53
osmosis
the flow of a solvent into a solution through a semipermeable membrane
54
semipermeable membrane
membrane with holes that allows molecules of a specific size to pass-through
55
what can pass through in osmosis
only the solvent
56
what can pass through in dialysis
both the solvent and other molecules of a limited size
57
what is osmotic pressure measured in?
atms
58
what can account for a large osmotic pressure
small concentrations
59
isotonic solutions
solutions with identical osmotic pressures
60
hypertonic solutions
have higher osmotic pressures & higher molarites
61
hypotonic solutions
have lower osmotic pressures & lower molarities
62
reverse osmosis
a pressure greater than osmotic pressure is applied causing the solvent to leave the solution- producing pure solvent
63
electrolyte solutions
solutions with ions (conduct electricty); alcohols are not electrolytic
64
i =
van't Hoff factor
65
why is the "i" sometimes less than expected?
ionic pairing
66
colloids
the suspension of tiny particles, that stay suspended because of electrostatic repulsion
67
what is the difference between a colloid & a solution
colloids scatter light & solutions do not
68
Ksp =
used to tell if a precipitate will occur or if all the solute will dissolve
69
Q > Ksp
ppt will form and only some solute dissolves
70
Q < Ksp
no ppt; all solute will dissolve + additional solute
71
Q = Ksp
all solute will dissolve but not additional solute
72
pH of acids
< 7
73
pH of bases
> 7
74
pH of alcohols
= 7
