# General chemistry 2 Ch12 chemical kinetics

## 27 terms · Final exam part one

### Chemical Kinetics:

The area of chemistry concerned with reaction rates and the sequence of steps by which reactions occur

### Reaction Rate

Either the increase in the concentration of a product per unit time or the decrease in the concentration of a reactant per unit time

Concentration change
Rate = _______________________
Time change

### Rate Law

An equation that shows the dependence of the reaction rate on the concentration of each reactant

### characteristics of First and second order reactions

Type A-->Products

### zeroth-order reaction

the rate is independent of the concentration of the reactant.

### Elementary Reaction vs overall reation

-A single step in a reaction mechanism, describes an individual molecular event.
-describes the reaction stoichiometry and is a summation of the elementary reactions.

### reactive intermediate

formed in one step and consumed in a subsequent step.

### Reactions

names from definations above

### Molecularity

A classification of an elementary reaction based on the number of molecules (or atoms) on the reactant side of the chemical equation.

uni, bi, tetra

### reaction rate laws and molecularity

The rate law for an elementary reaction follows directly from its molecularity because an elementary reaction is an individual molecular event

### Rate-Determining Step

The slowest step in a reaction mechanism. It acts as a bottleneck and limits the rate at which reactants can be converted to products

slow then fast

### Rate Laws for Overall Reactions:Initial Fast Step

fast then slow then fast

### k vs temprature

The rate constant is dependent on temperature

### Transition State

The configuration of atoms at the maximum in the potential energy profile. This is also called the activated complex.

### Collision Theory

As the average kinetic energy increases, the average molecular speed increases, and thus the collision rate increases.

calculating rate

### Activation Energy (Ea)

The minimum energy needed for reaction. As the temperature increases, the fraction of collisions with sufficient energy to react increases.

### Arrhenius equation

a different form of collision theory equation, where A(=pZ) is the frequency factor

### rate constant vs Ea vs T

k decreases as Ea increases
k increases as T increases (as before)

### Catalysis

A substance that increases the rate of a reaction without itself being consumed in the reaction. A catalyst is used in one step and regenerated in a later step.

Since the catalyst is involved in the rate-determining step, it often appears in the rate law.

### catalyzed vs uncatalyzed

Ea lower vs higher

### Homogeneous vs Heterogeneous Catalysts

A catalyst that exists in the same phase as the reactants.(iodide in decomposition of peroxide)
vs
A catalyst that exists in a different phase from that of the reactants.(commercial use eg. gas exhausted from automobile engines)

### More on heterogeneous

table on Heterogeneous catalysts