1
Q
Dispersion force
A
all liquids/solids experience; weakest force
- increases w/ increasing molar mass
2
Q
London force
A
dispersion force for nonpolar species
3
Q
dipole-dipole interaction
A
- polar molecules
- higher melting and boiling points
4
Q
hydrogen bonding
A
F-H, N-H, O-H
- highest melting and boiling points
5
Q
hydrophilic
A
water-soluble
- ions, polar molecules, H-bonds
6
Q
hydrophobic
A
water-insoluble
- hydrocarbons (alkanes)
7
Q
boiling point increases w/ increasing ___
A
- increasing molar mass
- increasing polarity
- increases greatly w/ hydrogen bonding
8
Q
branching disrupts ___
A
the amount of surface area molecules that interact
- decreases van der Waals interaction–>
- decreases boiling point
9
Q
dipole-dipole interactions, dipole-induced-dipole interactions, and dipole-induced-dipole-induced interactions occur b/w what molecules?
A
- dipole-dipole interactions: polar and polar molecule (no H-bonds)
- dipole-induced-dipole interactions: polar and non polar
- dipole-induced-dipole-induced interactions: nonpolar and nonpolar molecules
10
Q
triple point
A
- pressure and temperature at which solid, liquid and gas of a pure substance coexist in equilibrium
- the lowest pressure at which the liquid phase can exist
11
Q
below the triple point…
A
solid –> vapor or vapor –> solid
12
Q
critical temperature
A
lowest temp liquid and gas coexist
13
Q
melting point: molecular, ionic, metallic, covalent
A
- molecular: low (lowest)
- ionic: high
- metallic: hard to predict
- covalent: very high (highest)
14
Q
conductivity: molecular, ionic, metallic, covalent
A
- molecular: poor conductor
- ionic: poor conductor
- metallic: excellent conductors
- covalent: poor conductor
15
Q
strength: molecular, ionic, metallic, covalent
A
- molecular: soft
- ionic: hard but brittle
- metallic: ductile, malleable
- covalent: very hard and very brittle
16
Q
sheen: molecular, ionic, metallic, covalent
A
- molecular: dull
- ionic: dull
- metallic: shiny
- covalent: dull
17
Q
Is rate dependent upon concentration? Why or why not?
A
yes, as concentration increases, rate increases
18
Q
What is the significance of k? Is it dependent upon pressure? Temperature?
A
- k = rate constant
- depends on temp (not pressure)
19
Q
The half-life of which order reaction (0,1,2 which?) is independent of concentration?
A
1st
20
Q
the unit of a rate constant is always
A
M^-(order-1)*S^(-1)
21
Q
For which order reaction would reactant A be totally consumed in twice the half-life of the reaction?
A
0th order
22
Q
For which order does the concentration of the reactant decrease by 1⁄4 in twice the half-life of the reaction?
A
1st
23
Q
define equilibrium
A
rate forward = rate backwards
- forming reactants at same rate forming products
24
Q
Is an elementary step the same as an elementary reaction?
A
yes
25
What is the rate-limiting step?
- the slowest step
- determines overall rate of reaction
- Rslow = Roverall
26
what is an intermediate?
produced and consumed but not in overall reaction
- right --> left side (products --> reactants)
27
t/f: rate law depends on intermediates
FALSE (independent of intermediates, must substitute in rate expressions)
28
what is a catalyst?
produced and consumed but not in overall reaction
-left --> right side (reactants --> products)
29
Is concentration of catalyst allowed in a rate law (rate expression)?
it could be used
30
activation energy
minimum energy to start a reaction
31
activation energy depends on...
the substance (NOT temp, pressure, or concentration)
32
how does a catalyst impact activation energy?
decreases
33
K = ?
= K(forward)/K(backward)
= k1/k-1
= [products]^# / [reactants]^#
34
formation reaction
forming 1 mole of a compound from the 2 elements in their natural temp and pressure
35
what does a large K value mean?
mostly product at equilibrium, very little starting material
36
a small K value means...
mostly starting material, very little product
37
What quantity represents the extent of reaction?
how much product is made at equilibrium
38
K = 1 means...
molarities of reactions = molarities of products
39
K < 1 means...
favors the reactants
40
K > 1 means...
favors products
41
atoms with lone pairs are usually more ____, and differences in electronegativity between two atoms results in ____
electronegative
polarity
42
when are gases permanent gases at room temperature (25 dC?)
Tc < 25 dC
43
how does polarity effect boiling point? nonpolar?
polarity increases boiling point
- nonpolar has lower boiling point
44
polarizability depends on ____
molar mass (more polar = larger molar mass)
45
unit for k is found by ?
M^-(order - 1) S^(-1)
46
Rate =
change(concentration)/change(time)
47
The activation energy of a reaction A + B → C depends upon what property?
the nature of reactant species
48
What are minimal requirements for two molecules to react to form product?
- molecules must approach with the right orientation
- molecules must collide with minimal energy required to break bonds ( ≥ EA)
49
define reaction mechanism
Sequence of elementary steps (in complex reaction) describe in detail how the reaction proceeds
50
R overall ~ =
R slow
51
write the rate law for given steps:
Roverall = Rslow
- R = k (reactants slow)^(stoichiometry)
- substitute for intermediates
52
equation to solve for order "m" or "n"
Ln (R1/R2) = m * Ln(A1/A2)
53
where is the triple point on the phase diagram? the critical point?
triple point- where all 3 line segments meet
critical point- end of far line
54
what phase is below the line on the phase diagram? top left? top right?
- bottom: gas
- top left: solid
- top right: liquid
55
Common network covalent elements and compounds
common: Si, SiC, SiO2 (quartz), C (diamond), C (graphite), BN, Ge, ReB2, AIN
56
UNITS for temperature in Arrhenius equation
KELVIN (C + 273.15)
57
what substances are taken into account for the equilibrium constant expression (K)?
gases (g) and aqueous solutions (aq)
- not solid or liquids
- K = (products)/(reactants)
58
(Ms)^-1 = what order?
2nd
59
Le Chatelier’s Principle
if a system at equilibrium is disturbed by some change, then the system will shift so as to entirely or partially counteract the effect of the change
60
examples of changes for le chatelier's principle
- Adding or removing gaseous reactants or products
- Changing the volume or pressure of system
- Changing the temp
61
(LC) adding a gaseous species to the products will shift equilibrium to the
left
62
(LC) removing a gaseous species from the products will shift equilibrium to the
right
63
(LC) adding a gaseous species to the reactants will shift equilibrium to the
right
64
(LC) removing a gaseous species from the reactants will shift equilibrium to the
left
65
Le Chatelier's principle does not include...
- liquids or solid
- a gas that doesn't react with another species
66
(LC) increasing volume will shift equilibrium to...
the side with more gas moles
67
(LC) decreasing volume will shift equilibrium to...
the side with fewer gas moles
68
(LC) increasing pressure will shift equilibrium to...
the side with fewer gas moles
69
(LC) decreasing pressure will shift equilibrium to...
the side with more gas moles
70
(Van Hoff't) endothermic (+), raising temp shifts the equilibrium...
to more products
71
(Van Hoff't) endothermic (+), lowering temp shifts the equilibrium...
to more reactants
72
endothermic reactions...
need energy
73
exothermic reactions...
don't need energy (have enough)
74
(Van Hoff't) exothermic (-), raising temp shifts the equilibrium...
to more reactants
75
(Van Hoff't) exothermic (-), lowering temp shifts the equilibrium...
to more products
76
(Van Hoff't) exothermic (-), lowering temp shifts the equilibrium...
to more products
77
Would addition of a catalyst to a reaction increase the equilibrium constant?
NO- The only thing that changes an equilibrium constant is a change of temperature
78
what effects the equilibrium constant value?
ONLY temperature
79
Adding mass to one side, shifts equilibrium towards
The opposite side
80
Relationship between pressure and volume
Inverse (one increases, other decreases)
81
Delta (H) < 0 =
(-) delta H
Exothermic
82
Delta(H) > 0 =
(+)
Endothermic
83
Diatomic elements
Have no fear of ice cold bear
(Hydrogen, nitrogen, oxygen, iodine, chlorine, bromine)
84
concentration = ---/----
Mol / Volume
85
Reverse rate constant = (K)^?
K^(-1)
86
Q =
(products)/(reactants)
87
Q = K =
at equilibrium
88
Q ≠ K =
not at equilibrium
89
Q < K =
reaction moving to the right (products)
90
Q > K =
reaction moving to the left (reactants)
91
The addition of a buffer gas or of a pure solid (or pure liquid) causes ____ effect.
no effect
92
equilibrium table: extent of the reaction = ___ units
x atm
93
breaking bonds....
requires energy (endothermic)
94
making bonds...
releases energy (exothermic)
Chem 102
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