Reaction Rates + Rate Law
This is the study of the rates at which chemical reactions occur and the factors that affect them.
What is kinetics?
This is the time it takes for the concentration of a reactant to decrease to half its initial concentration.
What is half life?
This is a species which is produced by one elementary reaction, then consumed in a subsequent elementary step in a reaction mechanism.
What is an intermediate?
This is the elementary step in a reaction mechanism that occurs at the slowest rate.
What is the rate-determining step?
This is the difference in potential energy between the reactants and products of a reaction.
What is enthalpy of reaction (delta H)?
This is an equation which relates the concentrations of the reactants in a chemical reaction to the rate at which the reaction occurs.
What is the rate law?
This, plotted against time, will produce a linear graph for a first order overall reaction.
What is ln[A]?
This is the minimum amount of energy that a collision between particles must happen with in order for the reaction to occur.
What is activation energy?
Step 1: H2(g) + ICl(g) → HI(g) + HCl(g) slow
Step 2: HI(g) + ICl(g) → HCl(g) + I2(g) fast
This is the rate law for the above reaction mechanism.
What is k = [H2][ICl]?
This is equal to the number of peaks shown on a reaction energy profile.
What is number of steps?
A hypothetical chemical reaction occurs between three reactants, as shown below:
A + 2 B + C → AB2C
The rate law of the reaction is experimentally determined to be:
rate = k[B]2[C]
This is the reaction order with respect to A.
What is zero order?
This order reaction can be identified by the presence of a consistent half life.
What is first order?
Higher molecularity typically has this effect on reaction rate.
What is decreases reaction rate.
These are the necessary criteria that a reaction mechanism must meet in order to be considered valid.
What are...
- the sum of the elementary reactions must equal the overall balanced equation
- the rate determining step must produce the same rate law as experimentally determined?
This type of reaction has a positive overall energy change.
What is an endothermic reaction?
This is the overall reaction order for a reaction that is first order with respect to one reactant and second order with respect to the other.
What is third order?
This is the half life of ethane when it decomposes according to the reaction with a rate constant, k, of 5.36x10-4 s-1 at 973 K.
What is 21.5 minutes?
This is the catalyst in the following reaction:
Step 1: ClO- + H2O → HOCl + OH-
Step 2: Br- + HOCl → HOBr + Cl-
Step 3: OH- + HOBr → H2O + BrO-
What is H2O?
Step 1: H2(g) + NO(g) → H2O(g) + N(g) slow
Step 2: N(g) + NO(g) → N2(g) + O(g) fast
Step 3: O(g) + H2(g) → H2O(g) fast
This is the overall reaction represented by the above mechanism.
What is 2 H2(g) + 2 NO(g) → N2(g) + 2 H2O(g)?
This is the highest energy, unstable intermediate species formed between two stable compounds.
What is a transition state or activated complex?
In aqueous solution, the reaction represented by the balanced equation above has the experimentally determined rate law: rate = k[S2O82-][I-].
If the concentration of [S2O82-] is doubled while keeping [I-] constant, this is what will happen to the rate of the reaction.
What is rate of reaction doubles?
The conversion of cyclopropane gas, “A”, (0.25 M at t = 0) to propene gas, “B” is a first-order reaction with a rate constant, k, equal to 6.7x10-4 s-1 at 773 K.
A → B rate = k[A]
This would be the concentration of cyclopropane after 8.8 minutes. (hint: use integrated rate law)
What is 0.18 M?
Increasing this value for a reactant can increase reaction rate by increasing the frequency of collisions AND the probability of favorable orientation.
What is surface area?
The concentration of this type of species remains low throughout the course of a reaction.
What are intermediates?
This is how enzymatic catalysts speed up reactions.
What is by creating more favorable orientation for successful collisions?