Questions:
AP CHEMISTRY CHAPTER 14: CHEMICAL KINETICS(Pgs.574-614)
EQ: ______
Questions:
SECTION 1-Factors that Affect Reaction Rate-2•Chemical kinetics is the study of:
- Kinetics also looks at ______, which is a molecular-level view of ______
1)
2)
3)
4)
Physical State of the Reactants-4
•The more readily the reactants collide, the more ______they react.
•______reactions are often ______.
•______reactions that involve ______are faster if the surface area is ______; i.e., a fine powder reacts faster than a pellet or tablet. / Reactant Concentrations-5
- ______reactant concentration generally ______reaction rate.
Temperature-6
•______generally increases with ______.
•______energy of molecules is related to ______.
•At ______temperatures, molecules move more quickly, increasing numbers of ______and the energy the molecules possess during the collisions. / Presence of a Catalyst-7
•Catalysts affect rate without:
•Catalysts affect the kinds of ______, changing the ______(individual reactions that are part of the pathway from reactants to products).
•Catalysts are critical in many biological reactions.
SECTION 2-Reaction Rate-8
- Rate is:
- ______means ______
- [ ] means ______
- ______represents ______
- Types of rate measured:
-
- / Following Reaction Rates-9-10
- Rate of a reaction is measured using the:
Plotting Rate Data-11
•A plot of the data gives more information about rate.
•The slope of the curve at one point in time gives the ______.
•The instantaneous rate at time zero is called the ______rate; this is often the rate of interest to chemists.
•This figure shows ______and ______rate of the earlier example.
NOTE:
Relative Rates-12
•As was said, rates are followed using a reactant or a product. Does this give the same rate for each reactant and product?
•Rate is dependent on ______.
•If we followed use of C4H9Cl and compared it to production of C4H9OH, the values would be the same. Note that the______would have opposite signs—one goes down in value, the other goes up.
Rate =
Relative Rates and Stoichiometry-13
•What if the equation is not 1:1?
What will the relative rates be for: / SECTION 3-Determining Concentration Effect on Rate-14
•How do we determine what effect the concentration of each reactant has on the rate of the reaction?
Answer:
An Example of How Concentration Affects Rate-15
•Experiments 1–3 show how [NH4+] affects rate.
•Experiments 4–6 show how [NO2−] affects rate.
•Result: The rate law, which shows the relationship between rate and concentration for all reactants:
More About Rate Law-16
•The exponents tell the ______ of the reaction with respect to each reactant.
•In our example from the last slide:
•The order with respect to each reactant is ______. (It is first order in NH4+ and NO2−.)
•The ______is ______order (1 + 1 = 2; we just add up all of the reactants’ orders to get the reaction’s order).
•What is k? It is the ______. It is a ______-dependent quantity.
SECTION 4-First Order Reactions-17
Some rates:
Rate Law: / Relating k to [A] in a First Order Reaction-18
•rate = k [A]
•rate = −Δ [A] / Δt
•So: k [A] = −Δ [A] / Δt
•Rearrange to: Δ [A] / [A] = − kΔt
•Integrate: ln ([A] / [A]o) = − kt
•Rearrange: ln [A] = − k t + ln [A]o
•Note: this follows the equation of a line:
•So, a plot of ln [A] vs. t is ______.
An Example: Conversion of Methyl Isonitrile to Acetonitrile-19
•The equation for this reaction:
•It is first order: / Finding the Rate Constant, K-20
We can find the rate constant from:
Remember the integrated rate law:
The slope of the line will equal:
Half-Life-21
•Definition:
First Order Reaction:
•ln [A] = − k t + ln [A]o
•ln ([A]o/2) = − k t½ + ln [A]o
•− ln ([A]o/2) + ln [A]o = k t½
•ln ([A]o / [A]o/2) = k t½
•ln 2 = k t½ or t½ = 0.693/k / Second Order Reactions-22
•Some rates depend only on a ______to the second power.
•These are second order reactions.
•The rate law becomes:
Solving the Second Order Reaction for A → Products-23
•rate = k [A]2
•rate = − Δ [A] / Δt
•So, k [A]2 = − Δ [A] / Δt
•Rearranging: Δ [A] / [A]2 = − k Δt
•Using calculus: 1/[A] = 1/[A]o + k t
•Notice: / An Example of a Second Order Reaction: Decomposition of NO2-24
•A plot following NO2 decomposition shows that it must be second order because it is linear for 1/[NO2], ______ linear for ln [NO2].
•Equation:
Half-Life and Second Order Reactions-25
•Using the integrated rate law, we can see how half-life is derived:
•1/[A] = 1/[A]o + k t
•1/([A]o/2) = 1/[A]o + k t½
•2/[A]o −1/[A]o = k t½
•t½ = 1 / (k [A]o)
•So, half-life is: / Zero Order Reactions-26
•Occasionally, rate is ______of the ______of the reactant:
•Rate = k
•These are zero order reactions.
•These reactions are ______in concentration.
Factors that Affect Reaction Rate-27
1)
2)
3)
4) / SECTION 5-Temperature and Rate-28
•As temperature increases, ______
•The rate constant is ______dependent:
Rate constant ______with every ______deg. C rise.
Frequency of Collisions-29
•The ______is based on the ______.
•Molecules must ______to react.
•If there are more ______, more reactions can occur.
•So, if there are more ______, the reaction rate is ______.
•Also, if the temperature is higher, molecules move ______, causing more collisions and a higher rate of reaction.
The Collision Model-30
In a chemical reaction:
Molecules can only react if they: / Orientation of Molecules-31
•Molecules can often collide without forming ______.
•Aligning molecules properly can lead to chemical reactions.
•Bonds must be ______and made and atoms need to be in proper ______.
Energy Needed for a Reaction to Take Place (Activation Energy)-32
•Activation energy:
•An energy barrier must be overcome for a reaction to take place. / Transition State (Activated Complex)-33
•Reactants gain energy as the reaction proceeds until the particles reach the ______.
•The organization of the atoms at this highest energy state is called the ______ (or ______).
•The energy needed to form this state is called the ______.
Reaction Progress-34
•Plots are made to show:
•At the highest energy state, the ______state is formed.
•Reactions can be ______or ______after this. / Distribution of the Energy of Molecules-35
•Gases have an average temperature, but each individual molecule has ______.
•At ______energies, more molecules possess the energy needed for the reaction to occur.
The Relationship Between Activation Energy and Temperature-36
•Arrhenius noted relationship between activation energy and temperature:
•Activation energy can be determined graphically by reorganizing the equation: / Law vs. Theory-37
•Kinetics gives what happens. We call the description the ______.
•Why do we observe that rate law? We explain with a ______called a ______.
•A mechanism is a:
SECTION 6-Reaction Mechanisms-38
•Reactions may occur all at once or through several ______steps.
•Each of these processes is known as an ______or ______. / Molecularity-39
The ______of an elementary reaction tells how many ______are involved in that step of the mechanism.
Termolecular-40
•Termolecular steps require ______molecules to simultaneously collide with the proper ______and the proper ______.
•These are rare, if they indeed do occur.
•These ______ be ______than unimolecular or bimolecular steps.
•Nearly all mechanisms use only______- or ______reactions. / What Limits the Rate?-41
•The overall reaction cannot occur ______than the ______reaction in the mechanism.
•We call that the ______.
What is Required of a Plausible Mechanism?-42
•The ______ must be able to be devised from the rate-determining step.
•The ______must be obtained when all steps are added up.
•Each step must ______, like any equation.
•All ______are made and used up.
•Any catalyst is used and regenerated.
A Mechanism with a Slow Initial Step-43-45
•Overall equation:
•Rate law:
•If the first step is the rate-determining step:
•So, the first step of the mechanism begins:
•The easiest way to complete the first step is to make a product:
•We do not see NO3 in the stoichiometry, so it is an ______, which needs to be used in a faster next step.
•Since the first step is the slowest step, it gives the rate law.
•If you add up all of the individual steps (2 of them), you get the stoichiometry.
•Each step balances.
•This is a plausible mechanism. / A Mechanism with a Fast Initial Step-46-47
•Equation for the reaction:
•The rate law for this reaction is found to be
•Because ______processes are rare, this rate law suggests a multistep mechanism.
•The rate law indicates that a quickly established equilibrium is followed by a slow step.
•Step 1:
•Step 2:
What is the Rate Law?-48
•The rate of the overall reaction depends upon the rate of the ______step.
•The rate law for that step would be
How do we find [NOBr2]? / [NOBr2] (An Intermediate)?-49
•NOBr2 can react two ways:
–
–
•The reactants and products of the first step are in equilibrium with each other.
•For an equilibrium (as we will see in the next chapter):
The Rate Law (Finally!)-50
•Substituting for the forward and reverse rates:
•Solve for [NOBr2], then substitute into the rate law:
•This gives the observed rate law!: / SECTION 7-Catalysts-51
•Catalysts ______the rate of a reaction by ______the ______of the reaction.
•Catalysts ______the ______by which the process occurs.
Types of Catalysts-52
1)
2)
3) / Homogeneous Catalysts-53
•The ______and ______are in the same ______.
•Many times, reactants and catalyst are dissolved in the same solvent.
Heterogenous Catalysts-54
•The catalyst is in a ______phase than the ______.
•Often, ______are passed over a ______catalyst.
•The ______of the reactants is often the rate-determining step. / Enzymes-55
•______ are ______catalysts.
•They have a region where the reactants attach. That region is called the ______. The reactants are referred to as ______.
Lock and Key Model-56
•In the enzyme–substrate model, the ______fits into the ______of an______, much like a key fits into a lock.
•They are ______. /
SUMMARY
______