M3 Flashcards
(106 cards)
1
Q
can you predict product properties based on reactant properties ?
A
no (they emergent not a mix)
2
Q
if ΔG is positive, which way does the reaction go ?
negative ?
A
+ = forward
- = reverse
3
Q
what reactions are fast ?
slow ?
which goes to completion ?
A
- acid-base reactions
- iron rusting
- slow
4
Q
average reaction rate formula ?
A
Δx / Δt
Δx like (final-initial)
5
Q
are reactions inherently positive or negative ?
which one is negative ?
A
- positive (reverse reaction)
- forward reaction
6
Q
SOLVE: avg rate:
2N2O5 –> 4NO2 + O2
how does…
N2O5 disappear ?
NO2 appear ?
O2 appear ?
A
(-1/2 (ΔN2O5) / Δt) = 1/4 (ΔNO2 / Δt) = (ΔO2 / Δt)
2x as fast as O2 appears, half as fast as NO2 appears
4x as fast as O2 appears
1/4 as fast as NO2 appears, 1/2 as fast as N2O5 appears
7
Q
what is the equation for rate law ?
A
k [A]^x [B]^y
8
Q
when finding reaction order, what trials should be picked ?
A
those where wanted changes and other is constant
9
Q
what are the steps to find the reaction order ?
overall order ?
A
- pick trials
- do one element first: final/initial then its R (final/initial)
- what exponent is needed for the answer for A (or B etc) to equal the answer of R
- exponent = order
overall is just order of the A + B
10
Q
How to find k from a rate law ?
A
just plug it in and solve
11
Q
What are the units for k when reaction order is…
0 ?
1 ?
2 ?
3 ?
4 and etc ?
A
M/s
1/s
1/Ms
1/M^2s
1/M^3s
12
Q
what order is: ln[A]t = -kt + ln[A]0 ?
what does the -kt mean ?
A
1
negative slope
13
Q
what order is: [A]t = -kt + [A]0 ?
what does the -kt mean ?
A
0
negative slope
14
Q
what order is: 1/[A]t = kt + 1/[A]0 ?
what does the kt mean ?
A
2
positive slope
15
Q
What part of the rate law is temperature dependent ?
A
only k
16
Q
what is the transition state/activated complex ?
what is the KE there ?
A
highest point on graph
lowest
17
Q
can Ea be negative ?
A
nope
18
Q
if the reaction has reactants higher than products…
in the forward reaction:
what is the ΔH ?
which bonds are weaker ?
A
ΔH- (exothermic)
bonds broken
19
Q
What factors raise/affect rate ? why ? (4)
A
- temperature: higher temperature means more KE (more energy to overcome activation energy) = more collisions
- SA: more means more space for particles to attach
- concentration of reactants
- catalyst: reduces activation energy without being used up
20
Q
are all collision effective ?
A
no, they need to:
- collide
- in right direction
- with enough energy to overcome barrier
21
Q
are cold reactions slow or fast ? why ?
A
slow
only a small fraction of molecules had sufficient KE to form activation complex
22
Q
are hot reactions slow or fast ? why ? what happens to products ? Ea ?
A
fast
a larger fraction of molecules had sufficient KE to form activation complex (KE>Ea)
increase products
decrease Ea
23
Q
the arrhenius equation tells us that when temperature increases what happens to k ? when Ea increases ?
A
increases
decreases
24
Q
what is the rate determining step ?
A
that with the highest Ea
25
is the concentration of forward and reverse reactions the same at equilibrium ?
no, the rates are
25
during a reversible reaction, are both forward and reverse reactions occurring at the same time ?
yes
26
Le Chatelier's principle only applies to what ?
gases !
27
which reaction is favored when reactants are added ? is the equilibrium disturbed ?
forward
yes
28
which reaction is favored when products are added ? is the equilibrium disturbed ?
reverse
yes
29
does Le Chatelier's principle apply to all gases ?
not inert gases (last group nor N2)
30
temperature has a greater effect on which reaction ? which does it favor ?
the one with the highest Ea
- high temp favors highest Ea
- low temp favors lowest Ea
31
in an endothermic reaction, what is the comparison between Ear and Eaf ?
what happens to Kc as temp increases ?
Ear < Eaf
Kc increases
32
in an exothermic reaction, what is the comparison between Ear and Eaf ?
what happens to Kc as temp increases ?
Ear > Eaf
Kc decreases
33
what happens to the concentration of a gas when volume increases ?
decreases
decreases
34
what happens to the pressure of a when volume increases ? why ?
decreases since more volume means more space and less collisions
35
what happens to the molecules when there is high pressure ? what happens to Kc ?
molecules want to move to side with less molecules
nothing (it dont affect it)
36
when temperature rises in an exothermic reaction, is heat a product or reactant ? endothermic ?
product
reactant
37
do catalysts affect equilibrium ?
no
38
do inert gases affect equilibrium ?
nope
39
what is the difference between Q and K ?
Q is used when equilibrium is disrupted
K is used when there is equilibrium
40
what is the formula for Keq ?
K = [[C]^c) [D]^d]] / [[A]^a [B]^b]]
top being products and bottom reactants
41
what is the relationship between Q and K at the start of a reaction ?
Q < K
42
what happens to equilibrium when K = Q ?
K > Q ?
K < Q ?
at equilibrium
products/reactants are too small so reactants must decrease and prod. increase: equilibrium shifts right
products/reactants are too large so reactants must increase and prod. decrease: equilibrium shifts left
43
what is the sign of the change of reactants in ice tables ?
negative since they getting used up
44
when you know the value of K (forward reaction), how do you get the reverse reaction ?
1/K
45
what does it mean if K<1 ? if K>1 ?
products > reactants (reactants favored)
products < reactants (products favored)
46
if pH is given, how do you find the Ka and pKa ?
1. 10^-pH
2. Ka: chemical equation and solve for Ka = ([H+] [A-] / [HA]), top being the concentration gotten from step 1
3. pKa: -log (Ka)
47
if pH isn't given, how do you find the Ka and pH ?
1. Ka = 10^-pKa
2. ice table for Ka = ([H+] [A-] / [HA]) and solve
3. pH = -log[H+]
48
difference between ΔG and ΔG^0 ?
ΔG: actual free energy at nonstandard conditions
ΔG^0: standard free energy at standard conditions
49
formula for ΔG ? (ΔG^0 given)
ΔG = ΔG^0 + RT lnQ
50
what is the value of R ?
8.314 J/molK
51
how to convert from C to K ?
C + 273
52
how to convert from J to kJ ?
J divided by 1000
53
what does it mean when...
ΔG < 0
ΔG > 0
ΔG = 0
reaction is spontaneous; moving toward equilibrium (produces energy); ratef increases
reaction is nonspontaneous; moving away from equilibrium (requires energy); rater increases
reaction is at equilibrium; rate unchanged
54
formula for ΔG^0 when it's given ?
ΔG^0 = -RT lnK
55
what does it mean when...
ΔG^0 < 0
ΔG^0 > 0
ΔG^0 = 0
K>1 (prod > react)
K<1(prod < react)
K=0 (prod = react)
56
formula for ΔG if ΔH and ΔS given ?
ΔG=ΔH - TΔS
57
if the ΔH^0 and ΔS^0 is > 0, how is the reaction ?
spontaneous at high temps
58
if the ΔH^0 and ΔS^0 is < 0, how is the reaction ?
spontaneous at low temps
59
if the ΔH^0 < 0 and ΔS^0 > 0, how is the reaction ?
spontaneous
60
if the ΔH^0 > 0 and ΔS^0 is < 0, how is the reaction ?
nonspontaneous
61
ΔH is favorable when ?
-
62
ΔS is favorable when ?
+
63
How to find the concentration of H+ when M is given ?
it's the same
64
What is the acronym to remember reduction and oxidation ?
OIL RIG
(oxidation is losing)
(reduction is gaining)
65
The lower the pH of an acid, the what ?
the stronger the acid
66
strong acid = ?
high % ionization
67
How to find enthalpy change ?
bonds broken - formed
68
When bonds are being broken, it that an exo or endothermic process ? thermodynamically favorable when ?
endo-
at high temps
69
When temperature increases, how are the interactions between molecules of liquid A and molecules of liquid B ?
they are weaker than the interactions formed between liquid A and B when mixed
70
What is the trend of molecule size in the periodic table ?
increases down
71
Relationship between molecule size and strength of acid ?
larger size = stronger acid (weaker overlap of bonding orbitals)
72
What is the difference between a Lewis vs Bronsted acid and base ?
Lewis: deals with e- (base donates, acid receives)
Bronsted: deals with H+ (acid donates, base receives)
73
What are the rules for oxidation numbers ?
- lone atom = 0
- neutral atoms (no charges): add up to 0
- groups 1, 2, 15, 16, 17 always same number (+1, +2, -3, -2, -1) (specially H and O)
74
How to find in which compound a certain element has the highest possible oxidation number ?
compare the target element to the element is it bonded to in that molecule:
1. equal it to 0 and solve
example: H2S: H is +1, +2 due to the subscript --> 0= 2 + x and solve for x; = -2
2. highest one wins
75
What's an easy way to find which reaction is a redox ?
Has elements that are alone on one side and then part of a molecule on the other
76
When an acid has an OH- group alone, what does this mean ?
it's a weak acid
77
When an acid has carboxyl group (COOH), what does this mean ?
it's a strong acid
78
When comparing 2 molecules, how to know which is the electrophile and which is the nucleophile ?
- electrophile is the lewis acid
- nucleophile is the lewis base
- if both of lone pairs (usually means it's the base), then it's the one that's least electronegative
79
What is the electronegativity trend ?
increases across
80
How to find the OH when the H3O is given ?
What if the OH is given ?
(1 x 10^-14) / H3O
same thing: (1 x 10^-14) / OH
81
How to know what molecule is polar vs nonpolar ?
- polar: diff elements bonded to it or lone pairs (on central atom)
- nonpolar: same atoms
82
What are the IMF's and how to find them ?
- LDF (nonpolar)
- dipole-dipole (polar)
- H+ bonding: H bonded to ONF on both ends (and polar)
83
What's special about OH group ?
it's automatically polar
84
What is the rule for a solution to be missible ?
like dissolves like (polar and polar or nonpolar and nonpolar)
85
When something is heated, what does that make the reaction ? why ?
- endothermic
- raises temp which increases rotational and vibrational motions
86
How does the phase changes graph go ? entropy and enthalpy changes ? what happens to kinetic and potential energy when heating ?
as it goes up, it goes from solid at the very bottom to gas at the very top
- entropy increases up (more disorder/less tightly packed)
- enthalpy increases up (endothermic)
- as the temp increases, KE increases, PE constant
- temp constant (straight line), KE constant, PE increasing
(opposite - decreases- when cooling)
87
When something is slightly soluble in water, what happens when temp increases ?
solubility decreases (entropy is negative and makes gibbs negative at high temps)
88
What equation is used for the question :
A 45.0 mL sample of 0.531 M NH4NO3 is diluted with water to a total volume of 475.0 mL. What is the ammonium nitrate concentration in the resulting solution ?
M1V1=M2V2
89
What is the sign of entropy when something is insoluble ?
-
90
How to know order of highest to lowest enthalpy vaporization ?
highest = molecule with strongest IMFs
91
What group is always nonpolar ?
hydrocarbons
92
How to find hybridization ?
of atoms + # of lone pairs (on central atom)
93
How to find boiling point when entropy and enthalpy given ? What will always be the sign of G ?
G always = 0
ΔG=ΔH - TΔS
94
How to find which molecule is more soluble ?
highest charge or biggest
95
What does diatomic molecule mean ?
bonded to itself
N: N2
96
What does the positive sign of H mean when mixing ?
interactions between the same molecule (H2O and H2O) are stronger than diff molecules (H2O and urea)
97
If a mixed solution has a positive sign for S, which solution has higher S (before or after mixing)
After mixing
98
When something is polar, what happens to the bond dipoles ?
don't completely cancel out, leaving molecule with overall net dipole
99
VSEPR ? (electron geometry, molecule shape, bond angle) ?
- 2 center of density: linear, 180C
- 3: trigonal planar: 120C
- 1 lone pair (on central
atom): bent
- 4: tetrahedral: 109.5C
- 1 lone pair: trigonal
pyramidal
- 2 lone pair: bent
- 3 lone pair: bent
100
relationship between pKa and ea ?
pK increases = Ea decreases
(stronger acid)
101
When a reaction is exothermic, which is being made more ?
products
102
If a rate law is k[A]^2, and A and B are quadrupled, what do you do ?
[4]^2
103
relationship between Ka and acid strength ?
high Ka = stronger
104
When given a graph, how to tell which point belongs to Q>K ? 1
- more prod than reactants so point closest to prod
- point closest to react (more react than prod)
105
When the initial system % decreases, what happens to the equilibrium ?
shifts left since there's more prod
