Chemistry- Chapter 12 Kinetics

Change in amount (concentration, measured in molarity) of a reactant or product per unit of time, always positive

Rate at which reaction proceeds over time, using concentrations at the beginning and end of a time period

The rate at which a reaction is proceeding at a specific time and/or concentration

The instantaneous reaction rate at “time zero”

Rate at which different components of a reaction change relative to each other, depends on reaction stochiometry

mol L^-1 s^-1

1/s or s^-1

L mol^-1 s^-1

Rate = k [A]^0 = k

Rate = k [A]^1

Rate = k [A]² or k [A]^1 [B]^1

1. Chemical nature of reactants

2. Physical states of reacants (and their surface area)

3. Temperature (reactions faster at higher temps)

4. Concentrations (proportional increase)

5. Presence of a catalyst

A substance that increases reaction rate without being consumed by the reaction, usually lowers the reaction rate

Reactants and catalyst are in the same phase

Reactants and catalyst are in a different phase

The minimum energy necessary to form a product during a collision between reactants

On a graph, energy difference between reactants and transition state (peak)

1. Ea > kinetic energy of molecules: reaction occurs slowly (few fast molecules have enough energy to react)

2. Ea < kinetic energy of molecules: reaction occurs rapidly (large amount of molecules energetic enough)

1. Rate of reaction is proportional to # of collisions/time

2. Reacting species must collide in an orientation that allows contact between the atoms that will be bonded

3. Collision must occur with enough energy to allow for mutual penetration of reacting species valence shells, so e- can rearrange to form new bonds

The resulting unstable species of reactant species collide with proper orientation and enough energy, usually short lived and undetectable

Species that are produced in one step and consumed in another

The slowest elementary step of a reaction (which a reaction can’t proceed faster than), typically the first step of overal reaction