Unit 3: Solubility and Kinetics Flashcards
1
Q
Solubility
A
The maximum amount of solute that can be dissolved in a solvent at equilibrium
2
Q
Unsaturated solution
A
When the solute concentration is less than its equilibrium solubility concentration
3
Q
Saturated solution
A
When a solute concentration is equal to its equilibrium solubility concentration
ex. flat coke
4
Q
Supersaturated solution
A
When a solute concentration is greater than its equilibrium solubility concentration
5
Q
Precipitation Reactions general formula
A
AB(aq) + CD (aq) <=> AD(aq) + CB(s)
6
Q
A double-replacement reaction is where ____________ react to form ____________.
A
dissolved substances, one (or more) solid products
7
Q
The solid that is formed in a double-replacement reaction is known as a ___________.
A
precipitate
8
Q
The solution above the precipitate is called the __________.
A
supernatant
9
Q
The equation in which all ionic species (regardless of their physical state) are kept in their formula units, is called a ______________ or __________________.
A
molecular equation, formula unit equation
10
Q
Total ionic equations
A
include all ions and compounds in the reaction in the form they actually exist in the solution
11
Q
Net ionic equations
A
only include the ions forming a precipitate, and neglect to include ions remaining dissolved in solution (spectators)
Ions that are in the same form on both the reactant side and product side of the equation are canceled
12
Q
Always soluble:
A
Li+ Na+ K+ Rb+ Cs+ NH4+ NO3– ClO3– ClO4– CH3COO–
13
Q
Never soluble (except soluble when bonded with Group 1 elements and NH4+):
A
phosphate: PO43–
carbonate: CO32–
sulfite: SO32–
14
Q
Usually insoluble (except soluble when bonded with Group 1 elements and and NH4+ and some Group 2 elements):
A
OH– S2–
15
Q
When in doubt,
__________ compounds are usually insoluble.
A
Ag, Hg, and Pb
16
Q
Before a solution is saturated, a solid will _____________ dissolve. Once saturation is reached, the rate of dissolution of the solid and the rate of reforming the solid from dissolved ions are _____________ and the system is ___________
A
spontaneously, equal, at equilibrium
17
Q
Compounds that we call insoluble are those whose lowest free energy point for the dissolving process lies …
A
very close to 100% solid reactant(s) and nearly 0% ionic products.
18
Q
The ____________ is the equilibrium constant for the equilibrium between a slightly soluble ionic solid and a solution of its ions when the reaction is written as the solid dissolving into ions.
A
solubility product constant (Ksp)
19
Q
Since there is always only one solid reactant in a solubility chemical equation, there is never a __________ in a Ksp expression.
A
denominator
20
Q
When Qsp > Ksp, the reaction shifts to the ___________
A
reactants (to the left).
For solubility reactions, the solid is the reactant on the left. Thus, if Qsp > Ksp, the compound will precipitate.
21
Q
When Qsp < Ksp, the reaction shifts to the ____________
A
products (to the right).
For solubility reactions, the dissolved ions are the products on the right. Thus, if Qsp < Ksp, the ions remain dissolved.
22
Q
When Qsp = Ksp, the reaction is at _____________.
A
equilibrium
23
Q
molar solubility (x)
A
the number of moles per liter of the compound that will dissolve in a saturated solution
24
Q
just AB dissolving in water
Ksp equation?
A
Ksp = x^2
25
just A2B or AB2 dissolving in water
Ksp equation?
Ksp = 4x^3
26
just A3B or AB3 dissolving in water
Ksp equation?
Ksp = 27x^4
27
just A2B3 or A3B2 dissolving in water
Ksp equation?
Ksp = 108x^5
28
[ion] =
(x) (subscript)
29
x =
[ion] / subscript
30
to get grams per liter...
multiply moles/L x molar mass = g/L
31
to get molar solubility from g/L...
divide g/L by molar mass = mol/L
32
Ksp values for 3:2 or 2:3 ratios are ________
very small
33
the common ion effect occurs in a solution in which...
the same ion is provided by two different compounds.
34
will concentration of Mg2+ be greater if MgF2 is dissolved in pure water or in a solution of 0.1M sodium fluoride?
pure water
35
what is the molar solubility (x) of MgF2 in water?
Ksp = 4x^3
x = (Ksp/4)^1/3
36
what is the molar solubility (x) of MgF2 in 0.10 M NaF?
Ksp = [Mg2+] [F-]^2
solve for [Mg2+]
37
what is the molar solubility (x) of MgF2 in 0.10 M MgNO3?
Ksp = [Mg2+] [F-]^2
solve for [F-]
divide by 2 bc x = [ion] / subscript
38
Thermodynamics tells us about the _________ of a chemical reaction, whereas kinetics tells us about the __________ of the reaction.
energy, rate
39
If you calculate the reaction rate at t = 0, what rate did you just calculate?
instantaneous rate and initial rate
40
Any factors that causes molecules to __________________ speeds up the reaction rate
collide more frequently
41
The factors affecting the rates of a chemical reaction
Medium or Nature of the Reactants
Concentration (pressures for gases)
Temperature
A catalyst
42
For a reaction that is zero-order overall the rate...
does not change during the reaction.
43
Rate will also not change for a ___________ if you double or triple the concentration of reactant.
zero-order reaction
44
A catalyst...
speeds up the reaction by lowering activation energy but does not change K (equilibrium constant)
45
All else being equal, a reaction with a higher activation energy compared to one with a lower activation energy will...
proceed slower.
46
If the exponents in the rate-law do not match the coefficients in the balanced chemical equation, then we know that...
the reaction does not take place in one step.
47
Transition states are _______________.
short-lived
48
where is the reaction rate the fastest?
at the beginning
49
Reaction Rate
CH3Cl + OH- --> CH3OH + Cl-
rate = ?
-∆ [CH3Cl] /∆t = ∆ [CH3OH] /∆t
50
Reaction Rate:
the change in concentration of one of the reactants of products at a selected stage of the reaction divided by the time interval over which change takes place
51
___________ is the reaction rate at a specific moment in time or specific concentration
Instantaneous
52
___________ is the reaction rate over a defined time interval
Average
53
___________ is a single unique average rate of reaction that is uniform across all reactants and products
Unique average reaction rate
54
The instantaneous rate is the ___________ to the curve at the time of interest
slope of the tangent
55
Most instantaneous rates ___________ as the reaction proceeds.
decrease
56
The instantaneous rate of reaction at the start of the reaction is called the ____________
initial rate of reaction
57
the initial rate always has the unit:
concentration/time
rate = M/s (molarity over time)
58
The rate of the reaction depends on the __________ of the two reactants. This expression is known as the ___________.
concentrations, rate law
59
Some reaction rates depend heavily on the concentrations of the reactants, while other reaction rates do not. The __________ is the degree to which the reaction rate depends on the concentrations.
reaction order
60
Reaction orders can only be
0, 1, 2
61
_________ reaction order indicates that something other than concentration is determining rate of reaction.
zero
62
The __________ is unique to each rate law. The units depend on the overall order of the reaction.
rate constant, k,
63
units for rate constant (k) for zero-order reaction?
M x s-1
64
units for rate constant (k) for second reaction order?
M-1 x s-1
65
units for rate constant (k) for first reaction order?
s-1
66
____________ show concentration as a function of time
Integrated rate laws
67
integrated rate law for zero order:
[A] = [A]0 - kt
slope of int. rate law plot = -k
68
integrated rate law for first order:
ln[A] = ln[A]0 - kt
slope of int. rate law plot = -k
69
integrated rate law for second order:
1/[A] = 1/[A]0 + kt
slope of int. rate law plot = k
70
rate law for zero order:
rate = k
71
concentration vs. time plot for zero order:
negative linear until hits x-axis and trails straight
72
rate law for first order:
rate = k[A]
73
concentration vs. time plot for first order:
decreases exponentially
74
rate law for second order:
rate = k[A]^2
75
concentration vs. time plot for second order:
decreases exponentially (drops faster than first order, more concave)
76
empirical rate law
rate = k[A]^x [B]^y
77
____________ allows us to predict how long a reaction will take, or how much of the reactant remains after a certain amount of time.
Integrated rate laws
78
Half-life is the amount of time it takes for...
one half of [A]0 to react away.
79
The amount of reactant remaining after n half-lives is
[A] = (1/2)^n [A]0
80
Zero order:
As the concentration decreases, the half-life __________
decreases
81
First order:
As the concentration decreases, the half-life __________
remains constant
82
Second order:
As the concentration decreases, the half-life __________
increases
83
0th order half-life formula
t1/2 = [A]0 / 2k
84
1st order half-life formula
t1/2 = ln2 / k
85
2nd order half-life formula
t1/2 = 1 / k[A]0
86
Radioactive isotopes half-lives are __________ and do not depend on how much material is present
constant
first-order half life
87
All radioactive decay is ___________.
first-order
88
____________ is a distinct event in the progress of a reaction, often a collision of particles
Elementary Reaction
89
___________ is the number of reactant molecules, atoms, or ions in a specific elementary reaction
Molecularity
90
Unimolecular =
1 reactant
91
Bimolecular =
2 reactants
92
Termolecular =
3 reactants
93
___________ is a sequence of elementary reactions or steps that take place as reactants are transformed into products
Reaction Mechanism
94
An intermediate is ________ early in the mechanism and then _________ later, so it doesn't appear in the ____________.
produced, consumed, overall reaction
95
The rate of the overall reaction is determined by the rate of the ________________. This step is called the ____________ or _______________ step.
slowest elementary step, rate limiting step, rate determining step
96
If there is an intermediate in the slow step, you must find a way to ________ the reactant(s) that lead to the production of the intermediate.
swap out
97
higher concentration increases the __________ of collisions, resulting in a _________ reaction
frequency, faster
98
a solid reactant with a __________ creates offers more opportunities for reaction, so crushing large chunks of a solid into a fine powder results in a ________ reaction.
larger surface area, faster
ex. crushed ice melts in drink faster than regular cubed ice
99
reactant molecules have _______ at higher temperatures, so a larger number of reactant molecules can get over the ____________ hump.
more energy, activation energy
100
The rate constant k __________ with increasing temperature.
increases (exponentially)
101
All reactions go ________ at higher temperatures.
faster
102
Arrhenius Law formula
k = Ae^-(Ea/RT)
103
The _____________ is the rate constant at infinite temperature, or the theoretical maximum reaction rate possible.
pre-exponential factor A
104
_____________ is the minimum amount of energy that the reactants need in order to undergo a chemical reaction.
Activation energy Ea
105
The higher the activation energy, the _______ the temperature dependence of the rate constant
stronger
106
Low activation energies around 10 kJ/mol
temperature "independent"
107
High activation energies around 60 kJ/mol
temperature dependent
108
The same reaction at two different temperatures will have two different ___________.
rate constants
109
Arrhenius equation:
ln (k2/k1) = Ea/R (1/T1 - 1/T2)
110
_________ states that even if all the molecules have sufficient energy, not all interactions between reactants will lead to products.
Collision theory
111
On reaction coordinate plot, peaks are _______________
transition states or amount of steps in mechanism
112
On reaction-coordinate plot, number of valleys represents number of ___________
intermediates
113
If the reaction is endothermic in the forward direction, the activation is higher for the ________ direction than for the ________ direction.
The high Ea means that the rate constant of the ________ reaction depends more strongly on temperature than does the rate constant of the _____ reaction
forward, reverse
forward, reverse
114
If the reaction is exothermic in the forward direction, the activation energy is lower for the ________ direction than for the _______ direction.
The low Ea means that the rate constant of the ________ reaction depends more strongly on temperature than does the rate constant of the ________ reaction
forward, reverse
reverse, forward
115
For endothermic reactions: when the temperature increases, the _______ rate constant increases more than that of the _________ reaction.
forward, reverse
116
For exothermic reactions: when the temperature increases, the _______ rate constant increases more than that of the _______ reaction.
reverse, forward
117
If you increase the heat on an exothermic reaction, the ________ start to become more favored.
reactants
118
Collision theory only applies to...
Transition State Theory or Activated Complex Theory usually applies to...
molecules in the gas phase
molecules in solution
119
An ____________ is an arrangement of two molecules that can either go on to form products or fall apart again into the unchanged reactants.
The _________ have lengthened and weakened.
The ________ are only partly formed.
activated complex
original bonds
new bonds
120
In order for a reaction to occur, molecules have to get __________.
This causes their potential energies to increase due to two factors:
"too close"
1. proton-proton repulsions
2. electron-electron repulsions
121
If the initial KE of the reactants is less than the Ea...
no reaction will occur
122
A catalyst is _______ early in the reaction and _________ as a product later. It _______ appear in the overall reaction.
consumed, regenerated, does not
123
A catalyst is a compound or material that ________________ for the reactants to become products.
opens up a new reaction pathway (a new mechanism)
124
The new pathway has a _______ transition state energy than the original pathway
lower
125
The new pathway might have the _______ elementary steps or __________
the same number of, it might have more or fewer
126
The catalyst is the only factor that...
lowers the activation energy
127
Homogenous catalysts:
catalyst that is in the same phase as the reactants
128
Heterogenous catalysts:
catalyst that is in a phase different from that of the reactants
129
net ionic equation for the formation of precipitate
Copper (II) phosphate
3Cu2+ (aq) + 2PO43- (aq) <=> Cu3(PO4)2 (s)
130
net ionic equation for the formation of precipitate
Silver sulfite
Ag2+ (aq) + SO32- (aq) <=> Ag2SO3 (s)
131
net ionic equation for the formation of precipitate
Nickel (II) sulfide
Ni2+(aq) + S2- (aq) <=> NiS (s)
132
tin (IV) phosphate
Sn3(PO4)4
133
iodate
IO3-
134
IO3-
iodate
135
cesium (III) iodate
Cs(IO3)3
136
to determine what is most or least soluble you can't just go off ________, you have to __________
Ksp values, calculate molar solubility (or ballpark #'s)
137
The overall order of a reaction can be found by...
the sum of all the orders of the reactants
138
The reaction order is the relationship between _________ and ___________
reactant concentrations, the rate of a reaction
139
For solubility reactions, the dissolved ions are the _________ on the ________. Thus, if Qsp < Ksp, the ions __________.
products, right, remain dissolved
140
The Arrhenius equation is often used to compare the rate constants measured at two different temperatures. Using two sets of data points, the equation can be rearranged to yield...
This equation can also be written as...
ln(k2/k1) = Ea/R (1/T1 - 1/T2)
ln k = ln A - Ea/RT
141
Therefore if one measures rate constants at many temperatures and constructs a plot of _________ the slope of the plot would be ________ and the intercept will be ________
ln k vs 1/T
-Ea/R
ln A
